Question

Sodium Chromate $(N{a_2}Cr{O_4})$ is made commercially by:
A.Heating mixture of $C{r_2}{O_3}$ and $N{a_2}C{O_3}$
B.Heating mixture of chromite ore and sodium carbonate in the presence of oxygen
C.Heating sodium dichromate with sodium carbonate
D.Reacting $NaOH$ with chromic acid

Answer 1

Hint: We have to know that the sodium Chromate $(N{a_2}Cr{O_4})$ is a yellow hygroscopic compound and an intermediate in the extraction of chromium from its ores. Chromite (iron chromium oxide),$FeC{r_2}{O_4}$, is the most important chromium ore mineral. This is an oxide mineral. Chromium ores are used for preparing chromate salts.

Complete step by step solution:
We have to remember that the sodium Chromate $(N{a_2}Cr{O_4})$ is made commercially by heating a mixture of chromite ore and sodium carbonate in the presence of oxygen in a reverberatory furnace and liberates carbon dioxide.
We can write the chemical reaction for sodium chromate $(N{a_2}Cr{O_4})$ preparation as,
$4Fe{\left( {Cr{O_2}} \right)_2} + 8N{a_2}C{O_3} + 7{O_2}\xrightarrow{\Delta }8N{a_2}Cr{O_4} + 2F{e_2}{O_3} + 8C{O_2}$
This reaction converts chromium into chromates, leaving behind chromium ores.
Therefore, the option B is correct. (Heating mixture of chromite ore and sodium carbonate in the presence of oxygen)
In industries, we need to prepare a large amount of sodium chromate by the reaction of chromium oxide with sodium carbonate.
The chemical reaction for the vast scale preparation of sodium chromate by the reaction of $Chromium\left( {III} \right)Oxide$ $C{r_2}{O_3}$, roasting with sodium carbonate, $N{a_2}C{O_3}$.
\[2C{r_2}{O_3} + 4N{a_2}C{O_3} + 3{O_2} \to 4N{a_2}Cr{O_4} + 4C{O_2}\]
In the above reaction $Chromium\left( {III} \right)Oxide$ roasting with sodium carbonate,$N{a_2}C{O_3}$, in the presence of air.
Therefore, the option A is also correct.
Therefore, the option A and B is correct.

Note: We have to remember that the chromite is a mineral, it is also used to prepare other chromates. When sodium hydroxide, chromite ore and sodium nitrates are used for preparing sodium chromate in another method, subsequent to its formation, sodium dichromate is obtained by the conversion of chromate salt.
We have to know that the sodium chromate is used for conversion of primary and secondary alcohols to carboxylic acids and ketones respectively in organic chemistry. Also it is used in the petroleum industry for corrosion inhibitors.