13/ 15

Question

UCT ONLINE
HIGH SCHOOL
PHYSICAL SCIENCES
Pressure (kPa)
X
36
173
Temperature (K)
323
Figure 4: Graph showing temperature vs pressure.
Question 4.4.1 [1 mark]
What is the temperature of the water when the gas is at 36 kPa in Celsius?
Question 4.4.2 (3 marks]
Determine, by calculation, the value ofx.
Question 4.4.3 [4 marks]
Calculate the volume (in dm) of the gas at 173 K if it is given that 7 moles of gas
were used in this investigation.
Question 4.4.4 [1 mark]
What would be the effect on the pressure if the temperature stayed constant at
27 T but the volume of the gas increased?
TOTAL: 14
o 2019 Valenture Institute All Rights Reserved (not authorised for commercial use)

Answer 1

Answer:

4.4.1
To find the temperature of the water when the gas is at 36 kPa, we can use the graph provided.
At 36 kPa, the temperature is approximately 295 K.

Converting 295 K to Celsius:
Temperature in Celsius = Temperature in Kelvin - 273
= 295 K - 273
= 22°C

Therefore, the temperature of the water when the gas is at 36 kPa is 22°C.

4.4.2
To determine the value of x, we need to find the pressure at x kPa on the graph.
From the graph, we see that the pressure at x kPa is approximately 85 kPa.

Therefore, the value of x is 85 kPa.

4.4.3
The ideal gas law is: PV = nRT
Given:
Pressure (P) = 173 kPa
Temperature (T) = 173 K
Number of moles (n) = 7 moles
Gas constant (R) = 8.31 J/(mol*K)

Converting pressure to Pa:
P = 173 kPa * 1000 Pa/kPa = 173,000 Pa

Calculating volume:
V = (nRT)/P
V = (7 moles * 8.31 J/(mol*K) * 173 K) / 173,000 Pa
V ≈ 5.29 dm^3

Therefore, the volume of the gas at 173 K is approximately 5.29 dm^3.

4.4.4
If the temperature stays constant at 273 K but the volume of the gas increases, according to Boyle's Law, the pressure of the gas will decrease. This is because pressure and volume are inversely proportional when temperature is constant.

Therefore, the effect on the pressure would be that it decreases as the volume of the gas increases.

Total: 14 marks.