Chapter 7, Problem 49A

Interpretation Introduction

Interpretation:

The following reaction between calcium silicate and hydrogen fluoride needs to be balanced.

  ${\text{CaSiO}}_{\text{3}}\text{(s) + HF(g)}\to {\text{CaF}}_{\text{2}}{\text{(aq) + SiF}}_{\text{4}}{\text{(g) + H}}_{\text{2}}\text{O(l)}$

Concept Introduction:

• A chemical reaction is expressed as a chemical equation having reactants and products on left and right side of the reaction arrow respectively.

  $\text{Reactants }\to \text{ Products}$

• A balanced chemical equation is one in which the number of atoms of various elements on the reactants side is equal to that on the product side. It depicts the stoichiometry of a given reaction.
• The equations are balanced in two steps:

1) Balance the atoms by matching the number of atoms of each type on the reactants and product side.

2) Adjust the coefficients to the smallest whole number. A coefficient of '1' is implied and therefore not explicitly written.

Answer to Problem 49A

  ${\text{CaSiO}}_{\text{3}}\text{(s) + 6HF(g)}\to {\text{CaF}}_{\text{2}}{\text{(aq) + SiF}}_{\text{4}}{\text{(g) + 3H}}_{\text{2}}\text{O(l)}$

Explanation of Solution

The given equation involves the reaction between solid calcium silicate and hydrogen fluoride gas to form aqueous calcium fluoride, gaseous silicon tetrafluoride and water. The reactants and products are:

Reactants:

  $\begin{array}{l}{\text{Calcium silicate, solid - CaSiO}}_{\text{3}}\text{(s)}\\ \text{Hydrogen fluoride, gas - HF (g)}\end{array}$

Products:

  $\begin{array}{l}{\text{Calcium fluoride, aqueous - CaF}}_{\text{2}}\text{(aq)}\\ {\text{Silicon tetrafluoride, gas - SiF}}_{\text{4}}\text{(g)}\\ {\text{Water - H}}_{\text{2}}\text{O (l)}\end{array}$

Unbalanced equation:

  ${\text{CaSiO}}_{\text{3}}\text{(s) + HF(g)}\to {\text{CaF}}_{\text{2}}{\text{(aq) + SiF}}_{\text{4}}{\text{(g) + H}}_{\text{2}}\text{O(l)}$

The above equation is not balanced since the number of O, H and F atoms is 3, 1 and 1respectively on the reactants side while it is 1, 2 and 4 respectively on the products side. In order to balance the above equation, multiply HF by 6 and H₂O by 3 to get:

  ${\text{CaSiO}}_{\text{3}}\text{(s) + 6HF(g)}\to {\text{CaF}}_{\text{2}}{\text{(aq) + SiF}}_{\text{4}}{\text{(g) + 3H}}_{\text{2}}\text{O(l)}$

Conclusion

Therefore, 1 mole of calcium silicate reacts with 6 moles of hydrogen fluoride to form 1 mole of calcium fluoride, 1 mole of silicon tetrafluoride and 3 moles of water.