EXERCISE 23

CHEMICAL CHANGE

PAGE 285

1 Calculate the volume of the following gases at STP:

1.1 2 mol CO2;V = nVm

= 2 × 22,4= 44,8 dm3

1.2 3,3 mol of hydrogen gas;V = nVm

= 3,3 × 22,4= 73,92 dm3

1.3 0,45 mol neon.V = nVm

= 0,4 × 22,4= 10,08 dm3

2 Calculate the number of mol gas which is represented by each of the following volumes at STP:

2.1 150 dm3 oxygen gas;

Vn = Vm

150= 22,4= 6,7 mol

2.2 145 cm3 carbon(IV)oxide;V

n = Vm

145 × 10-3

= 22,4= 6,47 × 10-3 mol

2.3 32,4 ℓ argon.V

n = Vm

32,4= 22,4= 1,45 mol

3 Calculate the number of molecules/atoms that occurs in the following volumes of gas at STP:

3.1 240 dm3 nitrogen gas;V

n = Vm

240= 22,4= 10,71 mol

N = nNA

= 10,71 × 6,02 × 1023

= 6,45 × 1024 particles

3.2 437 cm3 carbon(IV) oxide;V

n = Vm

437 × 10-3

= 22,4= 1,95 × 10-2 mol

N = nNA

= 1,95 × 10-2 × 6,02 × 1023

= 1,17 × 1022 particles

3.3 41,4 ℓ xenon.V

n = Vm

41,4= 22,4= 1,85 mol

N = nNA

= 1,85 × 6,02 × 1023

= 1,11 × 1024 particles

4 Calculate the mass of gas that occurs in the following volumes of gas at STP:

4.1 240 dm3 nitrogen gas;V

n = Vm

240= 22,4= 10,71 mol

m = nM= 10,71 × 28= 299,88 g

4.2 437 cm3 carbon(IV) oxide;V

n = Vm

437 × 10-3

= 22,4= 1,95 × 10-2 mol

m = nM= 1,95 × 10-2 × 44= 0,86 g

4.3 41,4 ℓ xenon.V

n = Vm

41,4= 22,4= 1,85 mol

m = nM= 1,85 × 131= 242,35 g

5 Calculate the volume of each of the following Gases at STP:

5.1 45 g hydrogen gas;m

n = M45

= 2= 22,5 mol

V = nVm

= 22,5 × 22,4= 504 dm3

5.2 3,65 × 1024 molecules oxygen gas; Nn = NA

3,65 × 1024

= 6,02 × 1023

= 6,06 mol

V = nVm

= 6,06 × 22,4= 135,81 dm3

5.3 50 kg ammonia.m

n = M50 000

= 17= 2 941,18 mol

V = nVm

= 2 941,18 × 22,4= 65 882,35 dm3