Question

na₂s + 2hcl → 2nacl + h₂s
55g 15g 67g?
what is missing from the equation, and how do you know?
○a 73 grams of h₂s because the mass of the products must be double the mass of the reactants.
○b three grams of h₂s because the mass of the products must equal the mass of the reactants.
○c 143 grams of h₂s because the mass of the products must be three times the mass of the reactants.
○d 213 grams of h₂s because the mass of the products must be four times the mass of the reactants.

Explanation:

Step1: Calculate the mass of reactants

The mass of reactants is the sum of the mass of \(Na_2S\) and \(HCl\).
\(m_{reactants}=55g + 15g=70g\)

Step2: Use the law of conservation of mass

According to the law of conservation of mass, the mass of reactants equals the mass of products. Let the mass of \(H_2S\) be \(x\). Then \(m_{products}=67g+x\). Since \(m_{reactants} = m_{products}\), we have \(70g=67g + x\). Solving for \(x\), we get \(x=70g - 67g=3g\).

Answer:

B. Three grams of \(H_2S\) because the mass of the products must equal the mass of the reactants.