Question

Complete and balance each of the following equations for gas evolution reactions HCl(aq)+ZnS(s)>

Answer 1

2HCl(aq) + ZnS(s) ⇒ ZnCl₂(aq) + H₂S(g)

Further explanation  

Equalization of chemical reactions can be done using variables. Steps in equalizing the reaction equation:  

• 1. gives a coefficient on substances involved in the equation of reaction such as a, b, or c, etc.  
• 2. make an equation based on the similarity of the number of atoms where the number of atoms = coefficient × index (subscript) between reactant and product  
• 3. Select the coefficient of the substance with the most complex chemical formula equal to 1  

Reaction

HCl(aq) + ZnS(s) ⇒ ZnCl₂(aq) + H₂S(g)

1. give equation

aHCl(aq) + bZnS(s) ⇒ ZnCl₂(aq) + cH₂S(g)

2. make an equation

H, left=a, right=2c⇒a=2c(eq 1)

Cl, left=a, right=2⇒a=2⇒c=1(from eq 1)

Zn, left=b, right=1⇒b=1

So the equation :

2HCl(aq) + ZnS(s) ⇒ ZnCl₂(aq) + H₂S(g)