Question

How many grams of ZnCl2 will be produced from 26.0g of Zn and 42.0g of HCl. Round to three significant figures

Answer 1

Answer: The mass of zinc chloride that can be produced is 54.1 grams

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$     .....(1)

• For zinc:

Given mass of zinc = 26.0 g

Molar mass of zinc = 65.4 g/mol

Putting values in equation 1, we get:

$\text{Moles of zinc}=\frac{26g}{65.4g/mol}=0.397mol$

• For HCl gas:

Given mass of HCl gas = 42 g

Molar mass of HCl gas = 36.5 g/mol

Putting values in equation 1, we get:

$\text{Moles of HCl}=\frac{42g}{36.5g/mol}=1.15mol$

The chemical equation for the reaction of zinc and chlorine gas follows:

$Zn+2HCl\rightarrow ZnCl_2+H_2$

By Stoichiometry of the reaction:

1 mole of zinc reacts with 2 moles of HCl

So, 0.397 moles of zinc will react with = $\frac{2}{1}\times 0.397=0.794mol$ of HCl

As, given amount of HCl is more than the required amount. So, it is considered as an excess reagent.

Thus, zinc is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

1 mole of zinc produces 1 mole of zinc chloride

So, 0.397 moles of zinc will produce = $\frac{1}{1}\times 0.397=0.397moles$ of zinc chloride

Now, calculating the mass of zinc chloride from equation 1, we get:

Molar mass of zinc chloride = 136.3 g/mol

Moles of zinc chloride = 0.397 moles

Putting values in equation 1, we get:

$0.397mol=\frac{\text{Mass of zinc chloride}}{136.3g/mol}\\\\\text{Mass of zinc chloride}=(0.397mol\times 136.3g/mol)=54.1g$

Hence, the mass of zinc chloride that can be produced is 54.1 grams