DAS 12102/12203 Chapter 1 - Mole and Atomic Concept

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1-15 TUTORIAL QUESTIONS

1. Classify each of the following as an element, a compound, a homogeneous

mixture or a heterogeneous mixture:

(a) seawater (b) helium gas, (c) sodium chloride, (d) a bottle of soft drinks, (e)

milk-shake, (f) air in a bottle and (g) concrete.

2. Give the number of protons, neutrons and electrons for each of the following

species (a) O178

(b) Hg199

80and (c) Hg

200

80

3. Write the appropriate symbol for each of the following compounds: (a) Z = 74,

A = 186 (b) Z = 80, A = 201

4. Give the number of protons and electrons for each of the following ions: K+,

Mg2+, Fe3+, Br-, Mn2+, and Cu2+

5. What are the empirical formulas of the following compounds?

(a) Al2Br6 (b) Na2S2O4 (c) N2O3 (d) K2Cr2O7

6. How many moles of cobalt (Co) atoms are there in 6.00 X 109 (6 billion) of Co

atoms?

7. How many grams of gold (Au) are there in 15.3 moles of Au?

8. How many atoms are present in 3.14 grams of copper (Cu)?

9. Which of the following has a greater mass: 2 atoms of lead or 5.1 X 10-23

moles of helium?

10. Calculate the molar mass of the following substance (a) Li2CO3 (b) CS2 (c)

CHCl3 (d) C6H8O6 (e) KNO3 and (f) Mg3N2

11. How many molecules of ethane (C2H6) are present in 0.334g of C2H6 ?

12. Urea [(NH2)2CO] is used for the production of fertilizer and many other

products. Calculate the number of N, C, O and H atoms in 1.68 X 104 g of

urea.

13. Peroxyacylnitrate (PAN) is one of the components of smog. It is a compound

of C, H, N and O. Determine the percent composition of oxygen and the

empirical formula from the following percent composition by mass: 19.8% C,

2.50% H, and 11.6% N. What is the molecular formula given that its molar

mass is approximately 120g.

14. Tin (II) fluoride (SnF2) is often added to toothpaste as an ingredient to prevent

tooth decay. What is the mass of F in grams in 24.6 g of the compound?

DAS 12102/12203 Chapter 1 - Mole and Atomic Concept

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15. What are the empirical formulas of the compounds with the following

compositions? (a) 40.1% of C, 6.6% of H and 53.3% of O. (b) 18.4% C,

21.5% N and 60.1% K.

16. Balance up the following equations

(a) N2O5 N2O4 + O2

(b) KNO3 KNO2 + O2

(c) NH4NO3 N2O + H2O

(d) NH4NO2 N2 + H2O

(e) NaHCO3 Na2CO3 + H2O + CO2

(f) P4O10 + H2O H3PO4

(g) HCl + CaCO3 CaCl2 + H2O + CO2

(h) Al + H2SO4 Al2(SO4)3 + H2

17. Silicon tetrachloride (SiCl4) can be prepared by heating Si in chlorine gas

Si(s) + 2Cl2 (g) SiCl4(l)

In one reaction, 0.507 mole of SiCl4 is produced. How many moles of

molecular chlorine were used in the reaction?

18. Fermentation is a complex chemical process of wine making in which glucose

is converted into ethanol and carbon dioxide

C6H12O6 2C2H5OH + 2CO2

Starting with 500.4 g of glucose, what is the maximum amount of ethanol in

grams and liters that can be obtained by this process? (Density of ethanol =

0.789g/ml)

19. How many grams of KOH are present in 35.0 mL of 5.50 M solution?

20. Calculate the molarity of each of the following solutions. (a) 6.57 g of

methanol (CH3OH) in 1.50 X 102 mL solution, (b) 10.4 g of calcium chloride

(CaCl2) in 2.20 X 102 mL solution, and (c) 7.82 g of naphthalene (C10H8) in

85.2 mL of benzene solution.

21. Water is added to 25.0 mL of 0.866 M KNO3 solution until the volume of the

solution is exactly 500 mL. What is the concentration of the final solution?

22. You have 505 mL of 0.125 M HCl solution and you want to dilute it exactly to

0.100 M. How much water should you add?

DAS 12102/12203 Chapter 1 - Mole and Atomic Concept

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23. Calculate the concentration (in molarity) of NaOH solution if 25.0 mL of the

solution is needed to neutralize 17.4 mL of 0.312 M HCl solution.

24. What volume of 0.5 M HCl solution is needed to neutralize each of the

following; (a) 10 mL of 0.300 M NaOH solution, (b) 10 mL of 0.200 M Ba(OH)2

solution.

25. The SO2 present in air is mainly responsible for the acid rain phenomenon. Its

concentration can be determined by titrating against a standard

permanganate solution as follows:

5SO2 + 2MnO4- + 2H2O 5SO4

2- +2Mn2+ + 4H+

Calculate the number of grams of SO2 in a sample of air, if 7.37 mL of

0.00800 M KMnO4 solution is required for the titration.

26. The concentration of hydrogen peroxide solution can be conveniently

determined by titration against a standardized potassium permanganate

solution in acidic medium according to the following equation;

2MnO4- + 5H2O2 + 6H+ 5O2 + 2Mn2+ + 8H2O

If 36.44 mL of 0.01652 M KMnO4 solution is required to oxidize 25 mL of H2O2

solution, calculate the molarity of H2O2 solution.

1.

DAS 12102/12203 Chapter 1 - Mole and Atomic Concept

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Table 1.1: Mass of Atoms

Element Symbol Atomic

number (Z) Atomic mass

(A) Element Symbol

Atomic number (Z)

Atomic mass (A)

Actinium Ac 89 227.0278 Mercury Hg 80 200.59 Aluminum Al 13 26.98154 Molybdenum Mo 42 95.94 Americium Am 95 (243) Neodymium Nd 60 144.24 Antimony Sb 51 121.75 Neon Ne 10 20.179 Argon Ar 18 39.948 Neptunium Np 93 237.0482 Arsenic As 33 74.9216 Nickel Ni 28 58.70 Astatine At 85 (210) Niobium Nb 41 92.9064 Barium Ba 56 137.33 Nitrogen N 7 14.0067 Berkelium Bk 97 (247) Nobelium No 102 (259) Beryllium Be 4 9.01218 Osmium Os 76 190.2 Bismuth Bi 83 208.9804 Oxygen O 8 15.9994 Boron B 5 10.81 Palladium Pd 46 106.4 Bromine Br 35 79.904 Phosphorus P 15 30.97376 Cadmium Cd 48 112.41 Platinum Pt 78 195.09 Calcium Ca 20 40.08 Plutonium Pu 94 (244) Californium Cf 98 (251) Polonium Po 84 (209) Carbon C 6 12.011 Potassium K 19 39.0983 Cerium Ce 58 140.12 Praseodymium Pr 59 140.9077 Cesium Cs 55 132.9054 Promethium Pm 61 (145) Chlorine Cl 17 35.453 Protactinium Pa 91 231.0359 Chromium Cr 24 51.996 Radium Ra 88 226.0254 Cobalt Co 27 58.9332 Radon Rn 86 (222) Copper Cu 29 63.546 Rhenium Re 75 186.207 Curium Cm 96 (247) Rhodium Rh 45 102.9055 Dysprosium Dy 66 162.50 Rubidium Rb 37 85.4678 Einsteinium Es 99 (254) Ruthenium Ru 44 101.07 Erbium Er 68 167.26 Samarium Sm 62 150.4 Europium Eu 63 151.96 Scandium Sc 21 44.9559 Fermium Fm 100 (257) Selenium Se 34 78.96 Fluorine F 9 18.998403 Silicon Si 14 28.0855 Francium Fr 87 (223) Silver Ag 47 107.868 Gadolinium Gd 64 157.25 Sodium Na 11 22.98977 Gallium Ga 31 69.72 Strontium Sr 38 87.62 Germanium Ge 32 72.59 Sulfur S 16 32.06 Gold Au 79 196.9665 Tantalum Ta 73 180.9479 Hafnium Hf 72 178.49 Technetium Tc 43 (97) Helium He 2 4.00260 Tellurium Te 52 127.60 Holmium Ho 67 164.9304 Terbium Tb 65 158.9254 Hydrogen H 1 1.0079 Thallium Tl 81 204.37 Indium In 49 114.82 Thorium Th 90 232.0381 Iodine I 53 126.9045 Thulium Tm 69 168.9342 Iridium Ir 77 192.22 Tin Sn 50 118.69 Iron Fe 26 55.847 Titanium Ti 22 47.90 Krypton Kr 36 83.80 Tungsten W 74 183.85 Lanthanum La 57 138.9055 Uranium U 92 238.029

Lawrencium Lr 103 (260) Vanadium V 23 50.9414

Lead Pb 82 207.2 Xenon Xe 54 131.30

Lithium Li 3 6.941 Ytterbium Yb 70 173.04 Lutetium Lu 71 174.97 Yttrium Y 39 88.9059 Magnesium Mg 12 24.305 Zinc Zn 30 65.38 Manganese Mn 25 54.9380 Zirconium Zr 40 91.22 Mendelevium Md 101 (258)