Question

2) A student performs this reaction in the laboratory, and collects the hydrogen gas over water. The student collects 215.8 mL of gas. The total pressure is 755.2 mmHg and the temperature is 22.0 oC. c) Use the ideal gas law to calculate how many moles of hydrogen were produced in the reaction

Answer 1

Answer: 0.0086 moles of hydrogen are produced.

Explanation:

According to ideal gas equation:

$PV=nRT$

total pressure = 755.2 mm Hg

pressure of water at $22^0C$ =  19.8 mm Hg

P = pressure of hydrogen = (755.2-19.8) mm Hg = 735.4 mm Hg = 0.97 atm  

(760 mm Hg = 1atm)

V = Volume of gas = 215.8 ml = 0.2158 L

n = number of moles

R = gas constant =$0.0821Latm/Kmol$

T =temperature =$22.0^0C=(22.0+273)K=295K$

$n=\frac{PV}{RT}$

$n=\frac{0.97atm\times 0.2158L}{0.0821 L atm/K mol\times 295K}=0.0086moles$

Thus 0.0086 moles of hydrogen are produced.