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Question: If 10–4dm3 of water is introduced into a 1.0 dm3 flask at 300 K, how many moles of water are in the ...

If 10–4dm3 of water is introduced into a 1.0 dm3 flask at 300 K, how many moles of water are in the vapour phase when equilibrium is established ?

(Given :Vapour pressure of H2O at 300 K is 3170 Pa ; R= 8.314 J K–1mol–1)

A

5.56 × 10–3mol

B

1.53 × 10–2mol

C

4.46 × 10–2mol

D

1.27 × 10–3mol

Answer

1.27 × 10–3mol

Explanation

Solution

PV = nRT

V = 1 dm3 = 10–3 m3

P = 3170 Pa

R = 8.314 J K–1 mol–1

T = 300 K

3170 × 10–3 = n × 8.314 × 300

n=3170×1038.314×300=1.27×103mol.n = \frac{3170 \times 10^{- 3}}{8.314 \times 300} = 1.27 \times 10^{- 3}mol.