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