ANSWERS Multiple Choice Questions 1. (d) (ii) 20 moles of water = 20 ×18 g = 360 g of water, because mass of 1 mole of water is the same as its molar mass, i.e., 18 g. (iv) 1.2044 × 10 25 molecules of water contains × 25 A 1.2044 10 N number of moles, N A = 6.023×10 23 ∴ × = × 25 23 1.2044 10 20 moles 6.022 10 20 moles of water = 20×18 g = 360 g of water. 2. (a) Inert gases exist in monoatomic form. 3. (b) 4. (d) 5. (c) Weight of a sample in gram = number of moles × molar mass (a) 0.2 moles of C 12 H 22 O 11 = 0.2 × 342 = 68.4 g (b) 2 moles of CO 2 = 2×44 = 88 g (c) 2 moles of CaCO 3 = 2×100 = 200 g (d) 10 moles of H 2 O = 10×18 = 180 g 6. (d) Massof substance × Number of atoms in the molecule Numberof atoms = ×N A Molar mass ∴ (a) 18 g of water = A A 18 3 N 3N 18 × × = (b) 18 g of oxygen = A A 18 2 N 1.12 N 32 × × = (c) 18 g of CO 2 = A A 18 3 N 1.23N 44 × × = (d) 18 g of CH 4 = A A 18 5 N 5.63N 16 × × = 3 C hapter www.tiwariacademy.com
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
ANSWERS
Multiple Choice Questions
1. (d)
(ii) 20 moles of water = 20 ×18 g = 360 g of water, because mass of 1 moleof water is the same as its molar mass, i.e., 18 g.
(iv) 1.2044 × 1025 molecules of water contains
×25
A
1.2044 10
N number of moles, N
A = 6.023×1023
∴ ×
=×
25
23
1.2044 1020 moles
6.022 10
20 moles of water = 20×18 g
= 360 g of water.
2. (a) Inert gases exist in monoatomic form.
3. (b)
4. (d)
5. (c)
Weight of a sample in gram = number of moles × molar mass
(a) 0.2 moles of C12
H22
O11
= 0.2 × 342 = 68.4 g
(b) 2 moles of CO2 = 2×44 = 88 g
(c) 2 moles of CaCO3 = 2×100 = 200 g
(d) 10 moles of H2O = 10×18 = 180 g
6. (d)
Massof substance × Number of atoms in the molecule
Numberof atoms = × NAMolar mass
∴ (a) 18 g of water = A A
18 3N 3 N
18
×× =
(b) 18 g of oxygen = A A
18 2N 1.12 N
32
×× =
(c) 18 g of CO2 = A A
18 3N 1.23N
44
×× =
(d) 18 g of CH4 = A A
18 5N 5.63N
16
×× =
3Chapter
www.tiwariacademy.com
vipin.k
Pencil
vipin.k
Pencil
vipin.k
Pencil
vipin.k
Pencil
vipin.k
Pencil
vipin.k
Pencil
vipin.k
Pencil
vipin.k
Pencil
EXEMPLAR PROBLEMS102
7. (c)
1 g of H2 = A A
1N 0.5N
2× =
= 0.5×6.022×1023
= 3.011×1023
8. (a)
Mass of one atom of oxygen = Atomic mass/NA
=
×23
16g
6.022 10
9. (a)
Number of moles of sucrose =Massof substance
Molar mass
1
3.42 g0.01mol=
342 g mol−
=
1 mol of sucrose (C12
H22
O11
) contains = 11× NA atoms of oxygen
0.01 mol of sucrose (C12
H22
O11
) contains = 0.01 × 11 × NA atoms of oxygen
= 0.11× NA atoms of oxygen
Number of moles of water1
18g1mol=
18g mol−=
1 mol of water (H2O) contains 1×N
A atom of oxygen
Total number of oxygen atoms = Number of oxygen atoms from sucrose +
Number of oxygen atoms from water = 0.11 N
A + 1.0 N
A = 1.11N
A
Number of oxygen atoms in solution = 1.11 × Avogadro’s number
= 1.11 × 6.022 ×1023
= 6.68 × 1023
10. (c)
Short Answer Questions
11. (b) BiPO4— Both ions are trivalent
Bismuth phosphate
12. (a) CuBr2
(b) Al(NO3)
3
(c) Ca3(PO
4)
2
(d) Fe2S
3
(e) HgCl2
(f) Mg(CH3COO)
2
vipin.k
Pencil
vipin.k
Pencil
vipin.k
Pencil
vipin.k
Pencil
vipin.k
Pencil
103ANSWERS
13. CuCl2/ CuSO
4/ Cu
3 (PO
4)2
NaCl/ Na2SO
4/ Na
3 PO
4
FeCl3/ Fe
2(SO
4)3 / FePO
4
14. Anions Cations
(a) CH3 COO- Na+
(b) Cl– Na+
(c) It is a covalent compound
(d) 3NO−
4NH+
15. (a) CaF2
(e) Na2O
(b) H2S (f) CO, CO
2
(c) NH3
(d) CCl4
16. (a) Incorrect, the correct symbol of cobalt is Co
(b) Incorrect, the correct symbol of carbon is C
(c) Incorrect, the correct symbol of aluminium is Al
(d) Correct (He)
(e) Incorrect, the correct symbol of sodium is Na
17. (a) NH3
(b) CO (c) HCI (d) AlF3
(e) Mg S
N : H × 3 C : O H : Cl Al : F × 3 Mg : S
14 : 1 × 3 12 : 16 1 : 35.5 27 : 19 × 3 24 : 32
14 : 3 3 : 4 2 : 71 9 : 19 3 : 4
18. (a) 4 (b) 5
(c) 7 (d) 2
19. ~ 8/18
Mass of one mole (Avogadro Number) of neutrons ~ 1 g
Mass of one neutron = A
1g
Avogadro Number (N )
Mass of one molecule of water = A A
Molar mass 18g
N N=
There are 8 neutrons in one atom of oxygen
Mass of 8 neutrons = A
8
N
Fraction of mass of water due to neutrons ~ 8
18
vipin.k
Pencil
vipin.k
Pencil
vipin.k
Pencil
vipin.k
Pencil
EXEMPLAR PROBLEMS104
20. Yes, it is a temperature dependent property. The solubility generally,
increases with increase in temperature. For example, you can dissolve moresugar in hot water than in cold water.