Write the balanced equation for the reaction occurring when gold is dissolved in aqua regia.

Hint: As we know that in chemistry, equations play a major role. In the reaction three things are main. There are reactants, products and reaction conditions. The reactants are always on the left side of the equation. If more than one reactant in the equation means by using plus sign. The products are always on the right side of the reaction. Something here also follows. More than one product by using plus sign. In between reactant products are used arrows to find the reaction direction in the equation.

Complete answer:
When gold is dissolved in aqua regia to produce auric chloride and nitrosyl chloride.
The aqua regia is nothing but the mixture of acid in \[3:1\] ratio of hydrochloric acid and nitric acid in the solution form.
The chemical equation for the above discussion given below,
\[Au + HN{O_3} + {\text{3}}HCl \to HAuC{l_4} + NOCl + {H_2}O\]
The balanced chemical equation wise we can predict unknown products in the chemical reaction.
In chemistry, balances the chemical equation means,
We adjust the number moles of reactant and product used to attain an equal number of the same atom in reactant and product in the given chemical reaction.
The balanced chemical reaction is,
\[2Au + 3HN{O_3} + {\text{11}}HCl \to 2HAuC{l_4} + {\text{3}}NOCl + {\text{6}}{H_2}O\]
According to the above discussion and chemical reaction, we conclude the balanced equation for the reaction occurring when gold is dissolved in aqua regia is,
\[2Au + 3HN{O_3} + {\text{11}}HCl \to 2HAuC{l_4} + {\text{3}}NOCl + {\text{6}}{H_2}O\]

Note:
We have to remember that in balanced chemical reaction wise, we predict the side product of the reaction. In some cases we are not able to attain balance by changing the mole. In that case we use the number of countable ions in the product and reactant side of the chemical reaction. In chemistry, redox reaction is one of the types of major reactions. In this redox reaction two methods are used to attain the balanced chemical reaction. There are ion-electron methods and the oxidation number method.