HYBRIDIZATION PROBLEMS

Look at this diagram. Now think about hybridized sp2 orbitals. The above electron configuration is in the excited state, because one of electrons in the 2s orbital has promoted to the 2py orbital.
1. Write the electron configuration of this atom in the ground state.
2. Which atom has this electron configuration?
3. Why this hybridized orbital called sp2?
4. Give an example of the molecule which has hybridized sp2 orbitals.
5. Apply your understanding of hybridization to another example, for orbitals sp.
6. Explain hybridized sp3 orbitals for ammonia and water.
7. Compare the molecular geometry of methane, ammonia, and water.
8. Explain the reason why methane, ammonia, and water have different molecular shapes, although have the same hybridized orbitals.

ORBITALS PROBLEMS

Students, do you still open my blog? Of course, if you want to be the best student, so spend your time to learn something in this long holiday.
Do you remember these orbitals?
These orbitals are very important for elements in the A (main) groups.
1. How many orbital(s) is (are) in the s sub shell?
2. How many orbitals are in the p sub shells?
3. Do you remember, how many sub shells are maximum in an atom?
4. There are atoms that only have a s orbital. Whose are these elements?
5. Write the electron configuration of those elements.
6. There are 18 elements whose have s and p orbitals. Write the electron configuration of these elements.
7. What is the difference between px, py and pz orbitals?
8. What is the difference between 1s and 2s orbitals?

IONIC COMPOUNDS PROBLEMS

This task is about writing the chemical formulas of ionic compounds.
the numbers above periodic table at each group are the oxidation number of atom in their compounds. Remember, if the atom an element, the oxidation number is zero.
For ionic compounds, the oxidation number is the charge of the cations and anions.
Covalent compounds consist of atoms rather than ions, because there is an electron shared. The oxidation number indicated the number of electron shared (bonded electron pairs, BP). The minus sign indicates that the BP electrons is closely to the atom which has greater electronegativity. This discussing only focuses on the ionic compounds.
1. Write formula of compound between berilium and fluorine.
2. Find 10 (ten) formulas of ionic compounds.
3. Predict which compound from no. (2) has highest boiling point and give the reason.
4. Predict which compound has lowest boiling point and give the reason.

BOILING POINT OF WATER

When you boil liquid water, it will change to the gaseous state. Explain clearly step by step, from the first till the final. For example, you start from explaining water at room temperature is a liquid. This means that water molecules ..., so this molecule ... one of another; etc. Explain when you heat water, the molecules .... You can classify: before heating, during heating till boil, after boiling point. OK, do the best.

PRACTICAL WORK

Hallo students? What are you doing now? Spend a time to think about the equipments used in the chemistry laboratory as seen in the picture. Last time I have publish the similar equipments, and now I give you other pictures that more clear than the first, although the name of each equipment is still not clear; sorry about that. So this is another task for you to compare the table you have done before with these equipments. When you find equipments that you didn't have before, add these to your table.

There is another task I want to ask you. Please choose equipments that you often find or use in daily life and give an example of simple experiment or just a special observation at home using these equipments. Write down a plan and do the experiment or observation. Make a simple report in a scientific method. When you need a certain equipment, but you don't have this, you can modify by using something in your kitchen. It's OK, no problem, please do the best, it's a nice job.

COVALENT BONDING PROBLEMS

A hydrogen atom and a chlorine atom do not exist in the nature. They exist as hydrogen molecules, H2 and chlorine molecules, Cl2 because they are more stable as molecules rather than as atoms. Think about these and explain the reason.

When hydrogen gas and chlorine gas react one of another, as a result, hydrogen chloride, HCl is formed. Now what do you think about this process? Is it because the elements of H2 and Cl2 are less stable than HCl? If your answer is yes, so give me the reason. Remember, do not only say yes, OK? Always give the reason by using a strong argumentation. Write a paragraph to make a good explanation.

Don't forget to explain about duplet and octet systems; discuss the tendency of atoms in order to achieve their stability as same as the noble gas that the position is closely to these atoms, in the periodic table. Compare the Lewis structure of H2, Cl2, and HCl. Classify the type of covalent bonding, which is(are) a non polar covalent bond and which is (are) a polar one.

After you conclude the above concept, develop your knowledge by thinking about polar molecules and non polar molecules, the different polarity of molecules.

IONIC BONDING PROBLEMS

On the left hand side is a simple formation of ionic bonding between a sodium atom and a chlorine atom. Explain this formation by using a chemical equation. Look at the periodic table, choose a metal and a non metal, then write the equation.
Next, how about the equation of calcium if it combines with fluorine? The last, write the equation between potassium and oxygen.

STABILITY OF METALS PROBLEMS

It is a simple model of sodium or natrium atom. This atom has an atomic number 11. The electronic configuration of Na is (2, 8, 1). This atom doesn't exist in the nature. We never find it in our the daily life. Natrium is a metal in the IA group, periodic table of elements. In the nature we found it as a compound, the example is a table salt, sodium chloride, NaCl. What kind of compound NaCl is? You have thought before, this is an ionic compound, because metal combines with non metal, so there is a transfer of electrons from metal to non metal. NaCl(s) consists of Na+ ions and Cl- ions. These ions link together closely and forms a crystal.
The question is why natrium in the nature acts as Na+ ions in the NaCl rather than Na atoms? It is because of one electron of Na in the outer shell is not stable? If yes, what is the reason? Please explain clearly. After that, think about potassium and then calcium. Make a generalisation about the activity of metals.

CHEMICAL BONDING PROBLEMS

Please look at this picture and think carefully. Can you imagine and predict what kind of substance is that. OK students, keep thinking please. Do you think that is a substance which we call as a compound? Why do you think that is a kind of compound? Is that because it consists of two different particles? OK, it's right, good point.
Now, please think about the other thing, that is something which can hold all the particles together into the manner. To find the answer, use the information about anion and cation. To make simple, you can explain your answer by using examples, such as the anion is chloride, Cl- and the cation is sodium ion, Na+. You can write down your explanation and you can edit your answer latter. Use your knowledge about atomic structure, periodic properties, and chemical bonding. Do the best, please.

ELECTROCHEMICAL CELL PROBLEMS

This picture is a voltaic cell or we can call a Daniell cell. When the circuit is closed, the bulb lights brightly. Please explain clearly about this cell. After that, explain again for other cells, if the electrodes are changed with the following :

1. Cu - Fe

2. Mg - Fe

3. Ag - Zn

4. Fe - Sn

5. Ag - Cu

OK students, firstly you can think in a global manner, it's no problem. However, after that, you have to write down step by step clearly. A note is realy very important for you. To day you feel that you understand all the above problems. Unfortunately, if you don't think in dept and completely, latter perhaps you will find nothing in your mind about these concepts. So my suggestion is please do carefully everything you have to do, to develop your knowledge gradually.

ATOMIC STRUCTURE PROBLEM FOR RSBI X

1.Explain the meaning of atomos which stated by Democritus.
2.In his atomic theory, Dalton stated there are 5 important points. Explain clearly one by one.
3.Dalton stated atoms are identical, and different atoms have different properties. Explain by using examples.
4. Atom can not be created and destroyed. What is the effect of these?
5.Explain an experiment done by Thomson so that he found electrons in the atom.
6.How about Thomson’s atomic theory? Draw the atomic model and explain.
7.Atom is neutral, although Thomson has discovered electrons. What Rutherford thought about this before he did his experiment?
8.Explain an experiment done by Rutherford, until he concluded that in the atom there was a very small space in the center of atom, which has a positive charge.
9.Draw Rutherford’s atomic model and give the information.
10.Who found proton and neutron? Both particles were found by Rutherford?
11.After proton and neutron were discovered, draw completely the development of Rutherford’s atomic model.
12.Notation of uranium is 238-U with atomic number of 92. Determine the number of protons, neutrons, and electrons.
13.How many neutron(s) hydrogen atom has, if its number of mass is 1?
14. Explain the meaning of isotope, isoton, and isobar. Give examples.
15. Rutherford’s atomic model has a weakness. What is that? Explain the reason.
16. Niels Bohr has covered Rutherford’s weakness toward his theory. Explain what Niels Bohr did.
17.Draw atomic model of Niels Bohr.
18. Write down electronic configuration of 20 first elements, from hydrogen till calcium.
19.How many electrons are in the Mg2+ ion? Explain the reason.
20.Valence electrons of Mg is 2. Explain please.
21.In an atom, electrons are arranged as inner electrons and valence electrons. Explain please.
22.Metals always form positive ions. Why?
23.Metals can conduct electricity. Explain the reason.
24.Negative ions can be formed by non metal elements. Why?
25.If a metal forms a positive ion, what happen with the atom?
26.If a non metal forms a negative ion, what happen with the atom? Is it similar with metal?
27.What another name of positive ion and negative ion?
28.Neon-10, isoelectronic with Na+1, Mg+2, Al3+, F-, and O-2 ions. Explain please.
29.Write down electronic configurations of the above ions.
30.The abundance of Cl-35 and Cl-37 isotopes are 75% and 25%. Calculate the average of chlorine atomic mass.

COLLOID PROBLEMS

1. Explain the meaning of solvent, solute, filtrate, and precipitate

2. Explain the following terminologies: distillation, filtration, sedimentation, precipitation, and crystallization.

3. What makes water such a good solvent?

4. Classify the following mixtures: sugar and water, sand and water, milk, creamer, and oil

5. How do concentrated solutions differ from dilute solutions?

6. What happens when more solute is added to a saturated solution?

7. What is the size of particles in a solution?

8. What is a colloid?

9. What is one property of a suspension that is different from that of a solution or a colloid?

10. How is a colloid different than a suspension?

11. Which of the following statements about suspensions is correct?

12. Classify the following colloids according to dispersed phase and its medium: foam; cream, milk, paint, gelatine, hair spray, fog, mayonnaise, smoke, emulsion, and butter.

13. Give the type of colloids based on the dispersing medium and the dispersed substance below and give an example of each.
a. liquid – solid
b. gas – liquid
c. solid – liquid
d. solid – gas
e. liquid – gas

14. Give an example of emulsion in the daily life and explain how two make it. Explain the meaning of emulgator and give the reason why is it important in making emulsion.

15. Oil floats on water. Explain the most accurate reason for this.

16. Soap can be used as an emulgator. Explain and draw the interaction between the particles of soap, oil, and water.

17. Explain the following properties of colloid : Tyndall effect; Brown motion; electrophoresis; dialysis; electrodialysis; adsorption; and coagulation.

18. Colloid has a charge which can be positive or negative. Explain the reason.

19. Colloid can be stable and unstable. Give the reason.

20. How do we know the charge of colloid? Explain by giving an example.

30. How do we remove the excess of electrolytes in a colloid?

31. How do we purify a colloid? Is it the same as no. (30) above?

32. What is semipermeable membrane? What is it for?

33. Do you know cotrell tool? What is it for?

34. There are more than one method we use to coagulate a colloid. Which electrolyte can be used to coagulate a colloid that has a negative charge fastly? Which electrolyte can be used to coagulate a positive colloid fastly?

35. Explain the formation of “Delta” in the river.

36. What happen when two colloids that have different charge mix together.

37. There is an unstable colloid which need to be covered with other colloid. Explain and give an example.

38. What are the difference between liofil and liofob? Which one is more stable than the other one?

39. Explain about sulfur sol in water. Is it hydrofil or hydrofob?

40. What is gelatine? Explain please.

41. Vitamine D is a nonpolar vitamine. Is it soluble in water? Explain.

42. Colloid can be made by dispersion or condensation. Explain the difference.

43. How do we make the following colloid? Please explain.
a. gold sol from solid
b. paint from solid
c. AgCl sol from solution
d. sulfur sol from SO2 gas
e. Al(OH)3 sol from Al(OH)3 solid.
f. Fe(OH)3 from solution.
g. AgCl from solid.
h. As2S3 sol from As2O3(aq)

44. Tawas can be used for cleaning water. Explain please.

45. Poison in a certain fish can be removed by using a colloid. Explain please.

THE ANSWER OF ACID BASE TITRATION PROBLEMS

1. 25 mL of HCl(aq) is titrated with 0,10 M NaOH(aq). If the volume of NaOH needed is 30 mL,
a. Write down the ionic equation.
H+(aq) + OH-(aq) --> H2O(l)
b. What is the name of this reaction? Give the reason.
Neutralisation reaction. Because the H+ ions that give the
properties of acid react with the OH- ions that give the
properties of base form H2O which is neutral.
c. Calculate [HCl]
M1V1 = M2V2
M(HCl) x 25 = 0,10 x 30
M(HCl) = 0,12 mol/L
d. Calculate the pH before titration.
pH (HCl) = - log 0,12 = 2 – log (3 x 4)
= 2 – (log3 + 2log2)
= 2 – 1,1 = 0,9.
e. Calculate the pH of the equivalent point.
Strong acid titrated with strong base,
[H+] = [OH-]= √Kw = 10-7. pH = 7 (neutral)
f. Determine the indicator used in this titration.
The pH changes from 0,9 to 7, because at the equivalent
point the solution is neutral. So the appropriate indicator is
MM, pH range is 4,2 – 6,3. The color changes from red to yellow.
g. When the volume of NaOH(aq) which titrated to HCl(aq) is
15 mL, calculate the pH of solution.
H+(aq) + OH—(aq) --> H2O(l)
Initial 25 mL 0,12M 15 mL 0,10 M
3 mmol 1,5 mmol
Reaction 1,5 mmol 1,5 mmol
Final 1,5mmol 0
[H+] = 1,5 mmol/ (25 + 15) mL = 15/4 x 10-2 M
pH = - log 15/4 x 10-2 = 2 – (log 3 + log 5 – 2log2)
= 2 – (0,5 + 0,7 – 0,6) = 1,4.
h. If the volume of NaOH(aq) which titrated to HCl(aq) is 50
mL, calculate the pH of solution.
H+(aq) + OH—(aq) --> H2O(l)
Initial 25 mL 0,12M 50 mL 0,10 M
3 mmol 5 mmol
Reaction 3 mmol 3 mmol
Final 0 2 mmol
[OH--] = 2 mmol/ (25 + 50) mL = 2/75 M
pOH = - log 2/75 = – (log 2 - log 3 – 2log5)
= - 0,3 + 0,5 + 1,4 = 1,6.
pH = 14 – 1,6 = 12,4.
i. Draw the curve of the titration above.
















2. 25 mL of NaOH(aq) is titrated with 0,10 M HCl(aq). If the volume of NaOH needed is 20 mL,
a. Calculate [NaOH]
M1V1 = M2V2
M(NaOH) x 25 = 0,10 x 20
M(NaOH) = 0,08 mol/L
b. Calculate the pH before titration.
pOH(NaOH) = - log 0,08 = 2 – 3log2 = 2 – 0,9 = 1,1
pH(NaOH) = 14 – 1,1 = 12,9.
c. Calculate the pH of the equivalent point.
Strong base titrated with strong acid, at the equivalent point [H+] = [OH-]= √Kw = 10-7.
pH = 7 (neutral)
d. Determine the indicator used in this titration.
The pH changes from 12,9 to 7, because at the equivalent point the solution is neutral. So the appropriate indicator is PP, pH range is 8,3 – 10,0. The color changes from red to colorless.
e. When the volume of HCl(aq) which titrated to the base is 15 mL, calculate the pH of solution.
H+(aq) + OH—(aq) --> H2O(l)
Initial 10 mL 0,10M 25 mL 0,08 M
1 mmol 2 mmol
Reaction 1 mmol 1 mmol
Final 0 1 mmol
[OH-] = 1 mmol/ (25 + 15) mL = 1/4 x 10-1 M
pOH = - log 1/4 x 10-1 = 1 – (– 2log2) = 1 + 0,6 = 1,6.
pH = 14 – 1,6 = 12,4.
f. If the volume of HCl(aq) which titrated to the base is 25 mL, calculate the pH of solution.
H+(aq) + OH—(aq) --> H2O(l)
Initial 25 mL 0,10M 25 mL 0,08 M
2,5 mmol 2 mmol
Reaction 2 mmol 2 mmol
Final 0,5 mmol 0
[H+] = 0,5 mmol/ (25 + 25) mL = 0,5/50 M = 10-2 M
pH = - log 10-2 = 2.
g. Draw the curve of the titration above.





























3. 25 mL of CH3COOH(aq) is titrated with 0,10 M NaOH(aq). If the volume of NaOH needed is 30 mL. Ka = 2 x 10-5
a. Write down the ionic equation.
CH3COOH(aq) + OH-(aq) --> CH3COO-(aq) + H2O(l)
b. Calculate [CH3COOH]
M1V1 = M2V2
M(CH3COOH) x 25 = 0,10 x 30
M(CH3COOH) = 0,12 mol/L
c. Calculate the pH before titration.
[H+] = √Ka.Ma
[H+]= √2.10-5.0,12 = √24.10-7
pH = - ½ log 24.10-7
= 3,5 – ½ (log3 + 3 log2)
= 3,5 – ½ (0,5 + 3.0,3)
= 3,5 – 0,7
pH = 2,8.
d. Explain what happens at the equivalent point. Write down the ionic equation.
At the equivalent CH3COO-(aq), as a product, is hydrolyzed to form CH3COOH which is more stable than acetic ion.
CH3COO-(aq) + H2O(l) ↔ CH3COOH(aq) + OH-(aq)
e. Calculate the pH of the equivalent point.
n(CH3COO-) = n(NaOH) = 0,10 mmol/mL. 30 mL = 3 mmol. Vol. = 55 mL
[OH-] = √Kw/Ka x [CH3COOH]
= √ 10-14/2.10-5 x 3/55 = √ 10-10 x 3/11
pOH = - log √ 3.10-11 = 5,5 -1/2 log 3 = 5,5 – 0,25 = 5,25
pH = 14 – 5,25 = 8,75.
f. Determine the indicator used in this titration.
The pH changes from 2,8 to 8,75. So the appropriate indicator is PP which the pH range 8,3 – 10,0. The color changes from colorless to pink.
g. When the volume of NaOH(aq) which titrated to the acid is 15 mL, calculate the pH of solution.
CH3COOH(aq) + OH—(aq) --> CH3COO-(aq)+H2O(l)
Initial 25 mL 0,12M 15 mL 0,10M
3 mmol 1,5 mmol
Reaction 1,5 mmol 1,5 mmol 1,5 mmol
Final 1,5 mmol 0 1,5 mmol
[H+] = Ka x n acid / n base
[H+] = 2 x 10-5 x 1,5 / 1,5 = 2 x 10-5
pH = 5 – log 2 = 5 – 0,3 = 4,7.
h. If the volume of NaOH(aq) which titrated to the acid is 50 mL, calculate the pH of solution.
CH3COOH(aq)+OH—(aq) -->CH3COO-(aq)+H2O(l)
Initial 25 mL 0,12M 50 mL 0,10M
3 mmol 5 mmol
Reaction 3 mmol 3 mmol
Final 0 2 mmol
[OH-] = 2 / 75
pOH = – log 2 / 75
= – log2 + log 3 + 2 log5
= - 0,3 + 0,5 + 2 x 0,7 = 1,6.
pH = 14 – 1,6 = 12,4.
i. Draw the curve of the titration above.

ACID BASE TITRATION PROBLEMS

1. 25 mL of HCl(aq) is titrated with 0,10 M NaOH(aq). If the
volume of NaOH needed is 30 mL,

a. Write down the ionic equation.
b. What is the name of this reaction? Give the reason.
c. Calculate [HCl]
d. Calculate the pH before titration.
e. Calculate the pH of the equivalent point.
f. Determine the indicator used in this titration.
g. When the volume of NaOH(aq) which titrated to HCl(aq) is 15 mL, calculate the pH of solution.
h. If the volume of NaOH(aq) which titrated to HCl (aq) is 50 mL, calculate the pH of solution.
i. Draw the curve of the titration above.

2. 25 mL of NaOH(aq) is titrated with 0,10 M HCl(aq). If the
volume of acid needed is 20 mL,

a. Calculate [NaOH]
b. Calculate the pH before titration.
c. Calculate the pH of the equivalent point.
d. Determine the indicator used in this titration.
e. When the volume of HCl(aq) which titrated to the base is 15 mL, calculate the pH of solution.
f. If the volume of HCl(aq) which titrated to the base is 25 mL, calculate the pH of solution.
g. Draw the curve of the titration above.

3. 25 mL of CH3COOH(aq) is titrated with 0,10 M NaOH(aq). If the volume of NaOH needed is 30 mL,

a. Write down the ionic equation.
b. Calculate [CH3COOH]
c. Calculate the pH before titration.
d. Explain what happens at the equivalent point. Write down the ionic equation.
e. Calculate the pH of the equivalent point.
f. Determine the indicator used in this titration.
g. When the volume of NaOH(aq) which titrated to the acid is 15 mL, calculate the pH of solution.
h. If the volume of NaOH(aq) which titrated to the acid is 50 mL, calculate the pH of solution.
i. Draw the curve of the titration above.

THE ANSWER OF STOICHIOMETRY PROBLEMS Part 2

2. Hydrochloric acid is added to 1,3 grams of zink (Ar 65). If molarity of acid is 3 mol/L, answer the following questions.

a. 2HCl(aq) + Zn(s) --> ZnCl₂(aq) + H2(g)

2H+(aq)+2Cl-(aq)+Zn(s) --> Zn2+(aq) + 2Cl-(aq) + H2(g)

2H+(aq) + Zn(s) --> Zn2+(aq) + H2(g)

b.Determine the minimum volume of acid needed in this reaction.

n(Zn) = 1,3g/65g.mol-1 = 0,02 mol

n(HCl) = 2/1 . 0,02 = 0,04 mol

V(HCl) = 0,04 mol/3 mol/L = 0,013L= 13 mL

c. Calculate the gas produced at:

1) STP

n(H2) = 0,02 mol.
V(H2) = 0,02 mol x 22,4 L/mol= 0,448 L (448mL).

2) 1 atm and 27 degree's celcius

PV = nRT

1.V(H2) = 0,02. 0,082. 300

V(H2) = 0,492 L ( 492 mL)

3) the same T and P with nitrogen gas (Ar N = 14) that its mass of 1 L is 2 grams.

V(H2) = n(H2)/n(N2) x V(N2); n(N2) = 2/28 = 1/14 mol

V(H2) = 0,04/1/14 x 1L = 0,04 x 14 L = 0,56 L.

d. If zink used is 80% from its ore, calculate the mass of ore used.

Mass of ore = 100/80 x 1,3 g = 1,625 grams.

3. An aliage contains 90% of aluminium (Ar 27) and 10% of cuprum (Ar 63,5) is used to produce hydrogen gas. Hydrochloric acid is added to this aliage and produces 6,72 L gas at STP.

a. Write down the molecular equation and ionic equation.

2Al(s) + 6HCl(aq) --> 2AlCl3(aq) + 3H2(g)

2Al(s) + 6H+(aq)+6Cl-(aq) --> 2Al3+(aq)+6Cl-(aq)+3H2(g)

2Al(s) + 6H+(aq) --> 2Al3+(aq) + 3H2(g)

b. Calculate the mass of aliage.

n(H2) = 6,72L/22,4L.mol-1 = 0,3 mol

n(Al) = 2/3 x 0,3 mol = 0,2 mol.

m(Al) = 0,2 mol x 27 g/mol = 5,4 g

m(ore) = 100/90 x 5,4 g = 6 g.

c. If the minimum volume of acid used is 200 mL, predict the
molarity of this acid.

n(HCl) = 6/3 x 0,3 mol = 0,6 mol.

M(HCl) = 0,6 mol/0,2 L = 3 mol/L.

4. A mol of metal, M reacts with sulfuric acid 2M, produced 33,6 L hydrogen gas at STP. Answer the questions below.

a. Determine the formula of salt produced.

2M(s) + 3H2SO4(aq) --> M2(SO4)x(aq) + 3H2(g)
x = 3, Formula of salt = M2(SO4)3

n(H2) = 33,6 L / 22,4 L.mol-1 = 1,5 mol

b. Determine the oxidation number of M.

Oxidation number of M in salt is +3.

c. Write down the molecular equation and ionic equation.

2M(s) + 3H2SO4(aq) --> M2(SO4)3(aq) + 3H2(g)

2M(s)+6H+(aq)+3SO42-(aq)-->2M3+(aq)+3SO42-(aq)+3H2(g)

2M(s) + 6H+(aq) --> 2M3+(aq) + 3H2(g)

d. Calculate the minimum volume of acid needed.

n(H2SO4) = 3/3 x 1,5 mol = 1,5 mol

V(H2SO4) = 1,5 mol/ 2mol.L-1 = 0,75 L (750 mL)

5. FeS(Mr=88) is reacted with hydrochloric acid according to the following reaction:

FeS(s)+2HCl(aq) → FeCl2(aq)+H2S(g)

If this reaction produces 8 L of H2S gas, and at the same T and
P, 1 mol of H2S(g) = 20 L, answer the questions below.

a. Write down the ionic equation.

FeS(s)+2H+(aq)+2Cl-(aq) → Fe2+(aq)+2Cl-(aq)+H2S(g)

FeS(s) + 2H+(aq) → Fe2+(aq) + H2S(g)

b. Calculate the mass of FeS.

n(H2S) = 8L/20L.mol-1 = 0,4 mol

n(FeS) = 0,4 mol

m(FeS) = 0,4 mol x 88 g = 35,2 g

c. If an ore contains 70,4% FeS, calculate the mass of ore.

m(ore) = 100/70,4 x 35,2 g = 50%

d. The acid used is 4M. Determine the minimum volume of acid needed.

n(HCl) = 2/1 x 0,4 mol= 0,8 mol.

V(HCl) = 0,8 mol / 4 mol.L-1 = 0,2 L (200 mL)

THE ANSWER OF STOICHIOMETRY PROBLEMS Part 1

1.Write down the molecular equation and ionic equation, then state the name of the products.

a.Ba(OH)2(aq)+2HCl(aq)--> BaCl2(aq) + 2H2O(l)
Barium chloride
Ba2+(aq)+2OH-(aq)+2H+(aq)+2Cl-(aq)-->Ba2+(aq)+2Cl-(aq)+2H2O(l)
OH-(aq) + H+(aq) --> H2O(l)

b.CH3COOH(aq)+NaOH(aq)--> CH3COONa(aq)+H2O(l)
Sodium acetate
CH3COOH(aq)+Na+(aq)+OH(aq)-->CH3COO-(aq)+Na+(aq)+H2O(l)
CH3COOH(aq)+OH(aq)-->CH3COO-(aq)+H2O(l)

c.H2SO4(aq)+2NH3(aq)-->(NH4)2SO4(aq)
Ammonium sulfate
2H+(aq)+SO42-(aq)+2NH3(aq)-->2NH4+(aq)+SO42-(aq)
2H+(aq)+2NH3(aq)-->2NH4+(aq)

d.CaO(s) + 2HCl(aq) --> CaCl2(aq) + H2O(l)
Calcium chloride
CaO(s)+2H+(aq)+2Cl-(aq)-->Ca2+(aq)+2Cl-(aq)+H2O(l)
CaO(s)+2H+(aq)-->Ca2+(aq)+H2O(l)

e.CO2(g)+Ca(OH)2(aq)--> CaCO3(s)+H2O(l)
Calcium carbonate
CO2(g)+Ca2+(aq)+2OH-(aq)-->CaCO3(s)+H2O(l)

f.2HCl(aq)+Ca(s)--> CaCl2(aq)+H2(g)
Calcium chloride
2H+(aq)+2Cl-(aq)+Ca(s)-->Ca2+(aq)+2Cl-(aq)+H2(g)
2H+(aq)+Ca(s)-->Ca2+(aq)+H2(g)

g.H2SO4(aq)+Mg(s)--> MgSO4(aq)+H2(g)
Magnesium sulfate
2H+(aq)+SO42-(aq)+Mg(s)-->Mg2+(aq)+SO42-(aq)+H2(g)
2H+(aq)+Mg(s)-->Mg2+(aq)+H2(g)

h.6H2SO4(aq)+2Fe(s)-->Fe2(SO4)3(aq)+3SO2(g)+6H2O(l)
Iron(III) sulfate, sulfur dioxide
12H+(aq) + 6SO42-(aq) + 2Fe(s) --> 2Fe3+(aq) + 3SO42-(aq) + 3SO2(g)+ 6H2O(l)
12H+(aq) + 3SO42-(aq) + 2Fe(s) --> 2Fe3+(aq) + 3SO2(g)+ 6H2O(l)

i.8HNO3(aq)+3Zn(s)-->3Zn(NO3)2(aq)+2NO(g)+4H2O(l)
Zink nitrate, nitrogen monooxide
8H+(aq)+8NO3-(aq)+3Zn(s)-->3Zn2+(aq)+6NO3-(aq)+2NO(g)+4H2O(l)
8H+(aq)+2NO3-(aq)+3Zn(s)-->3Zn2+(aq)+2NO(g)+4H2O(l)

j.2HNO3(aq) + Ag(s) --> AgNO3(aq) + NO2(g) + H2O(l)
Silver nitrate, nitrogen dioxide
2H+(aq)+2NO3-(aq)+Ag(s)-->Ag+(aq)+NO3-(aq)+NO2(g)+H2O(l)
2H+(aq)+NO3-(aq)+Ag(s)-->Ag+(aq)+NO2(g)+H2O(l)

k.AgNO3(aq) + NaCl(aq) --> AgCl(s) + NaNO3(aq)
Silver chloride, Sodium nitrate
Ag+(aq)+NO3-(aq)+Na+(aq)+Cl-(aq)-->AgCl(s)+Na+(aq)+NO3-(aq)
Ag+(aq)+Cl-(aq)-->AgCl(s)

l.NH4Cl(aq)+NaOH(aq) --> NaCl(aq) + NH3(g) + H2O(l)
Sodium chloride,ammonia
NH4+(aq)+Cl-(aq)+Na+(aq)+OH-(aq)-->Na+(aq)+Cl-(aq)+NH3(g)+H2O(l)
NH4+(aq)+OH-(aq)-->NH3(g)+H2O(l)

STOICHIOMETRY PROBLEMS

1.Write down the molecular equation and ionic equation, then state the name of the products.
a.A solution of barium hydroxide reacts with hydrochloric acid
b.Acetic acid reacts with a solution of sodium hydroxide.
c.Sulfuric acid reacts with a solution of ammonia.
d.Calcium oxide reacts with hydrochloric acid.
e.Carbon dioxide is added to calcium hydroxide solution.
f.Hydrochloric acid is added to calcium.
g.Dilluted sulfuric acid is added to magnesium.
h.Concentrated of sulfuric acid is added to iron.
i.Dilluted nitric acid is added to zink.
j.Concentrated nitric acid is added to silver.
k.A solution of silver nitrate reacts with a solution of table salt produces a precipitate.
l.A solution of ammonium chloride is added to a solution of sodium hydroxide, a gas will be produced.

2.Hydrochloric acid is added to 1,3 grams of zink (Ar 65). If molarity of acid is 3 mol/L, answer the following questions.
a.Write down the molecular equation and the ionic equation.
b.Determine the minimum volume of acid needed in this reaction.
c. Calculate the gas produced at:
1)STP
2)1 atm and 27 degree's celcius
3)the same T and P with nitrogen gas that its mass of 1 L is 2 grams.
d.If zink used is 80% from its ore, calculate the mass of ore used.

3.An aliage contains 90% of aluminium (Ar 27) and 10% of cuprum (Ar 63,5) is used to produce hydrogen gas. Hydrochloric acid is added to this aliage and produces 6,72 L gas at STP.
a.Write down the molecular equation and ionic equation.
b.Calculate the mass of aliage.
c.If the minimum volume of acid used is 200 mL, predict the molarity of this acid.

4.A mol of metal, M reacts with sulfuric acid 2M, produced 33,6 L hydrogen gas at STP. Answer the questions below.
a.Determine the formula of salt produced.
b.Determine the oxidation number of M.
c.Write down the molecular equation and ionic equation.
d.Calculate the minimum volume of acid needed.

5.FeS(Mr=88)is reacted with hydrochloric acid according to the following reaction:
FeS(s)+2HCL(aq) → FeCl2(aq)+H2S(g)
If this reaction produced 8 L of H2S gas, and at the same T and P, 1 mol of H2S gas = 20 L, answer the questions below.
a.Write down the ionic equation.
b.Calculate the mass of FeS.
c.If an ore contains 70,4% FeS, calculate the mass of ore.
d.The acid used is 4M. Determine the minimum volume of acid needed.