1. A mixture contains 9 gram each of H2O and NaCl, what is the mole fraction of NaCl?
a) 0.15
b) 0.23
c) 0.45
d) 0.64
Explanation: Mole fraction of NaCl = (9/58.5)/[9/58.5 + 9/18] = 0.23.
2. A mixture contains 10 grams each of CH4, H2O, and SO2, what is the mole fraction of CH4?
a) 0.14
b) 0.31
c) 0.46
d) 0.67
Explanation: Mole fraction of CH4 = (10/16)/[(10/16) + (10/18) + (10/64)] = 0.46.
3. A mixture contains 80% of HCl and 20% H2O by weight, what is the mole fraction of HCl?
a) 0.15
b) 0.29
c) 0.45
d) 0.66
Explanation: Mole fraction of HCl = (80/36.5)/[(80/36.5) + (20/18)] = 0.66.
4. A mixture contains 80% of NaOH and 20% H2O by weight, what is the mole fraction of NaOH?
a) 0.24
b) 0.42
c) 0.64
d) 0.78
Explanation: Mole fraction of HCl = (80/40)[(80/40) + (20/18)] = 0.64.
5. A compound contains 40% of Sulphur and 60% of Oxygen, what is the empirical formula of the compound?
a) SO2
b) SO3
c) SO4
d) None of the mentioned
Explanation: Mole fraction of Sulphur = (40/32)[(40/32) + (60/16)] = 0.25, => Mole fraction of oxygen = 0.75, => Empirical formula of compound is SO3.
6. What is the molecular weight of a mixture that contains 25% CO2, 40% O2 and 35% N2?
a) 11.2 g
b) 22.4 g
c) 33.6 g
d) 44.8 g
Explanation: Molecular weight = (25*44 + 40*32 + 35*28)/100 = 33.6 g.
7. What is the weight of 10 moles of a mixture with composition 15% O2, 25% SO2, 30% COCl2, 25% SO3 and 5% N2?
a) 124
b) 345
c) 507
d) 719
Explanation: Molecular weight of mixture = (15*32 + 25*64 + 30*99 + 25*80 + 5*28)/100 = 71.9, => Weight of mixture = 71.9*10 = 719.
8. If a compound contains 48% of Carbon, 48% of oxygen and 8% of hydrogen by weight, then what is the possible molecular formula of the compound?
a) C2H4O
b) CH4O3
c) C4H4O3
d) C4H8O3
Explanation: Ratio of number of atoms, Carbon: Hydrogen: Oxygen = 48/12: 8/1: 48/16 = 4:8:3.
9. A compound contain 12% of carbon, 16% of oxygen, 28% of nitrogen, 4% of hydrogen and 40% calcium by weight, then what can be the possible formula of the compound?
a) C2H3N2Ca(OH)
b) CH4N4Ca2(OH)
c) CH3N2Ca2(OH)
d) None of the mentione
Explanation: Ration of number of atoms, carbon: hydrogen: oxygen: nitrogen: calcium = 12/12: 4/1: 16/16: 28/14: 40/20 = 1:4:1:2:2.
10. What is the value of x in C2H8(OH)x if the percentage by weight of hydrogen is 12%?
a) 1
b) 2
c) 3
d) 4
Explanation: Let the total weight of the compound be 100 g, => weight of hydrogen in the compound is 12 g, => x = 12 – 8 = 4.