Question

100 c.c of oxygen is collected over water at 23°C and 800mm pressure. If vapour pressure of water vapours at 23°C is 21.00mm, then calculate volume of the gas at NTP.

Options

A
100 c.c
B
94.53 c.c
C
150 c.c
D
90.0 c.c

Explanation

To find the volume of oxygen at NTP, we use the formula P1V1/T1 = P2V2/T2, adjusting for water vapor pressure:

1. Subtract the vapor pressure of water from the total pressure to get the pressure of dry oxygen: P1 = 800mm - 21mm = 779mm.

2. Substitute the known values: P1 = 779mm, V1 = 100 c.c, T1 = 296K; P2 = 760mm, T2 = 273K.

3. Rearrange the formula to solve for V2: V2 = (P1 * V1 * T2) / (P2 * T1).

4. Substitute and calculate: V2 = (779 * 100 * 273) / (760 * 296) ≈ 94.53 c.c.

Therefore, the correct volume at NTP is 94.53 c.c. Options A, C, and D result from errors in calculation or misunderstanding of the conditions.

This option incorrectly assumes no change in volume after adjustments for temperature and pressure.

Correct! After adjusting for vapor pressure, temperature, and pressure, this is the volume at NTP.

This option overestimates the volume due to incorrect temperature and pressure adjustments.

This option underestimates the volume, possibly from incorrect calculations or assumptions.