Question

In the laboratory hydrogen gas is usually made by the following reaction:Zn(s)+2HCl(aq)=H2(g)+ZnCl2(aq)How many liters of H2 gas , collected over water at an atmospheric pressure of 752 mmHg and a temperture of 21 Co, can made from 3.566 g of Zn and excess HCl?the partial pressure of water vapor is 18.65mmHg at 21C0.A) 0.68LB) 2.72LC) 1.36LD) 1.33LE) 0.0975L

Answer 1

Answer:

The correct answer is option C, that is, 1.36 L.

Explanation:

The reaction mentioned in the question is:  

Zn (s) + 2HCl (aq) ⇒ H2 (g) + ZnCl2 (aq)

It is clear that one mole of zinc is generating one mole of hydrogen gas as seen in the reaction. The mass of zinc mentioned in the question is 3.566 grams, the no of moles can be determined by using the formula,  

n = mass / molecular mass

The molecular mass of zinc is 65.39 g/mol, now putting the values in the formula we get,  

n = 3.566 g/ 65.39 g/mol

= 0.0545 mol

Based on the question, the partial pressure of water vapor is 18.65 mmHg and the atmospheric pressure is 752 mmHg. Therefore, the pressure of hydrogen gas will be,  

Pressure of hydrogen gas (H2) = 752 mmHg - 18.65 mmHg

= 733.35 mmHg

The liters of hydrogen gas produced can be calculated by using the equation, PV =nRT

R is the gas constant, having the value 62.36 L mmHg/K/mol and T is the temperature (273 + 21 = 294 K).  

Now putting the values in the equation we get,  

733.35 mmHg * V = 0.0545 mol * 62.36 mmHg/K/mol * 294 K

= 999.19 L / 733.35

= 1.36 L

Hence, the volume of hydrogen gas is 1.36 L.