Chapter - 7 molar mass, balancing equations, and chemical reactions

Question 1

Small particles such as atoms, molecules, and ions are counted using the mole, a unit called Avogadro’s number that contains 6.02 × 1023 items.

Answer 1

1 mole = 6.02 × 1023 items
Avogadro’s number
602 000 000 000 000 000 000 000 = 6.02 × 1023

Avogadro’s number is named for Amedeo Avogadro (1776–1856), an Italian physicist.

Question 2

Avogadro’s number, 6.02 × 1023, can be written as equality and as two conversion factors.

Answer 2

Equality:1 mole = 6.02 × 1023 particles
Conversion Factors:
1 mole/ 6.02 x 10 to 23 particles

Question 3

What is the number of atoms in 2.0 mole of Al?

A. 2.0 Al atoms
B. 3.0 × 10 to the 23 Alatoms
C. 1.2 × 10 to the 24 Al atoms

Answer 3

Answer is C.

Question 4

Calculate the number of moles in each of the following.

91.0 g of Ag

Answer 4

AMU of Ag = 107.9

moles of Ag =91.0g×1mole/107.9g=0.843 mole

Question 5

Calculate the number of moles in each of the following.

0.248 g of C

Answer 5

AMU of C= 12

ans= 0.0206 mol or 2.06 x 10 to the-2

Question 6

Calculate the number of moles in each of the following.

12.0 g of ammonia, NH3

Answer 6

NH3=N+3H=14.0+3(1.0)=17

12.0gNH3 x 1molNH3/17gNH3 = 0.706 mol

Question 7

Calculate the number of moles in each of the following.

6.25 g of CH4

Answer 7

ans = 0.390 mol

Question 8

Calculate the number of moles in each of the following.

183g of Fe2O3

Answer 8

ans = 1.15 mol

Question 9

Balance:

Zn(s)+HNO3(aq)⟶Zn(NO3)2(aq)+H2(g)

Answer 9

Zn(s)+2HNO3(aq)→Zn(NO3)2(aq)+H2(g)

Question 10

Balance:

Al(s)+H2SO4(aq)⟶Al2(SO4)3(aq)+H2(g)

Answer 10

2Al(s)+3H2SO4(aq)→Al2(SO4)3(aq)+3H2(g)

Question 11

Balance:

K2SO4(aq)+BaCl2(aq)⟶KCl(aq)+BaSO4(s)

Answer 11

K2SO4(aq)+BaCl2(aq)→2KCl(aq)+BaSO4(s)

Question 12

Balance:

CaCO3(s)⟶CaO(s)+CO2(g)

Answer 12

CaCO3(s)⟶CaO(s)+CO2(g)