Small quantites of hydrogen gas can be prepared in the laboratory by the addition of aqueous hydrochloric acid to metallic zinc. Typically, the hydrogen gas is bubbled through w…

Question

asked May 19, 2020 143k views

1 Answer

Yashesh · Answer 1 · 2020-05-23T11:51:03+0000

Answer: The mass or zinc reacted is 0.624 grams.

Step-by-step explanation:

We are given:

Total pressure = 1.032 atm

Vapor pressure of water = 32 torr = 0.042 atm (Conversion factor: 1 atm = 760 torr)

To calculate partial pressure of hydrogen gas, we use the equation:

$p_(H_2)=p_T-p_(H_2O)\\\\p_(H_2)=1.032-0.042=0.99atm$

To calculate the number of moles of hydrogen gas, we use the equation given by ideal gas follows:

PV=nRT

where,

P = pressure of hydrogen gas = 0.99 atm

V = Volume of hydrogen gas = 240. mL = 0.240 L (Conversion factor: 1 L = 1000 mL)

T = Temperature of hydrogen gas =
30^oC=[30+273]K=303K

R = Gas constant =
$0.0821\text{ L. atm }mol^(-1)K^(-1)$

n = number of moles of hydrogen gas = ?

Putting values in above equation, we get:

$0.99atm* 0.240L=n* 0.0821\text{ L atm }mol^(-1)K^(-1)* 303K\\n=(0.99* 0.240)/(0.0821* 303)=9.55* 10^(-3)mol$

The chemical equation for the reaction of zinc and hydrochloric acid follows:

$Zn+2HCl\rightarrow ZnCl_2+H_2$

By Stoichiometry of the reaction:

1 mole of hydrogen gas is produced from 1 mole of zinc metal

So,
9.55* 10^(-3)mol of hydrogen gas is produced from =
(1)/(1)* 9.55* 10^(-3)=9.55* 10^(-3)mol of zinc metal

To calculate the mass of zinc metal, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Molar mass of zinc = 65.38 g/mol

Moles of zinc =
9.55* 10^(-3) moles

Putting values in above equation, we get:

$9.55* 10^(-3)mol=\frac{\text{Mass of zinc}}{65.38g/mol}\\\\\text{Mass of zinc}=(9.55* 10^(-3)mol* 65.38g/mol)=0.624g$

Hence, the mass or zinc reacted is 0.624 grams.