Question

Baking powder is a commonly used dry leavening agent consisting of a mixture of carbonate, bicarbonate and a weak acid. It used to make a cake is a mixture of starch, $NaHC{O_3}$ and $Ca{\left( {{H_2}P{O_4}} \right)_2}$. The function of $Ca{\left( {{H_2}P{O_4}} \right)_2}$ is:
A) To slow down the release of $C{O_2}$
B) Being acidic in nature and give $C{O_2}$ when moistened with $NaHC{O_3}$
C) To act as fille
D) None of these

Answer 1

Hint: Baking powder is a combination of calcium dihydrogen phosphate ($Ca{\left( {{H_2}P{O_4}} \right)_2}$) and sodium bicarbonate ($NaHC{O_3}$). In baking powder $Ca{\left( {{H_2}P{O_4}} \right)_2}$ acts as a leavening agent.


Complete answer:
Baking powder is a combination of an acid, base and a buffering material to control the reaction between acid and base before the actual use. $Ca{\left( {{H_2}P{O_4}} \right)_2}$ present in baking powder acts as a leavening agent. Since it is acidic in nature when combined with an alkali component, commonly used base is sodium bicarbonate ($NaHC{O_3}$) or potassium bicarbonate ($KHC{O_3}$), it then react with them producing carbon dioxide ($C{O_2}$) and salt.
Baking powder in dry state is stable and there will not be any reaction between any components. But when a liquid is added to it the two chemicals mainly calcium dihydrogen phosphate ($Ca{\left( {{H_2}P{O_4}} \right)_2}$) and sodium bicarbonate ($NaHC{O_3}$) forming a solution.
In liquid state dihydrogen phosphate ($Ca{\left( {{H_2}P{O_4}} \right)_2}$) and sodium bicarbonate ($NaHC{O_3}$) react quickly, by donating a proton to the bicarbonate ion to form carbonic acid. The carbonic acid produced will then decompose into carbon dioxide ($C{O_2}$) and water. This release of carbon dioxide gas is responsible for the rising of cakes, cookies, bread which gives the texture to it.
$Ca{\left( {{H_2}P{O_4}} \right)_2} + 2NaHC{O_3} \to 2C{O_2} + 2{H_2}O + N{a_2}HP{O_4} + CaHP{O_4}$

$\therefore $Option (B) is the answer.


Note: Calcium dihydrogen phosphate ($Ca{\left( {{H_2}P{O_4}} \right)_2}$) is a leavening agent and produce carbon dioxide and due to its outward pressure causes the rising effect in cakes, cookies etc. It also includes components to improve their stability and consistency. A buffering material is added in order to prevent the reaction between acid and base before their intended use.