Borax is prepared by treating colemanite with:A.) {NaNO_3}B.) NaClC.) {Na_2CO_3}D.) NaHCO_3

To determine how borax is prepared from colemanite, let's first understand the compounds involved:

- **Colemanite** is a naturally occurring mineral, primarily composed of calcium borate \((Ca_2B_6O_{11} \cdot 5H_2O)\).
- **Borax** (sodium borate) is generally represented as \((Na_2B_4O_7 \cdot 10H_2O)\).

The preparation of borax from colemanite involves a chemical reaction where sodium carbonate \((Na_2CO_3)\) is used to react with colemanite. The reaction proceeds as follows:

1. **Reaction**: When colemanite is treated with sodium carbonate, it leads to the formation of borax and calcium carbonate as a byproduct. The simplified reaction can be represented as:
\[
Ca_2B_6O_{11} \cdot 5H_2O + Na_2CO_3 \rightarrow Na_2B_4O_7 \cdot 10H_2O + CaCO_3 + H_2O
\]

In this reaction:
- **Sodium carbonate** provides the sodium ions necessary to form borax.
- **Calcium carbonate** is formed as a byproduct.

Now, examining the options:

A.) \(\text{NaNO}_3\) (sodium nitrate)
B.) \(\text{NaCl}\) (sodium chloride)
C.) \(\text{Na}_2\text{CO}_3\) (sodium carbonate)
D.) \(\text{NaHCO}_3\) (sodium bicarbonate)

The correct answer is **C.) \(\text{Na}_2\text{CO}_3\)**. This is the reagent used to prepare borax from colemanite.