Question

What is the formula of baking soda?
(A). $NaHC{O }_{ 3 }$
(B). ${ Na }_{ 2 }{ CO }_{ 3 }$
(C). ${ Na }_{ 2 }{ SO }_{ 4 }$
(D). NaCl

Answer 1

Hint: Baking soda is also known as sodium bicarbonate. It is a crystalline white solid which commonly appears as a white powder.

Complete step-by-step solution -

Since baking soda is known as sodium bicarbonate, its formula is NaHC${O }_{ 3 }$. It is also chemically known as sodium hydrogen carbonate. It is soluble in water. It is a salt formed by the neutralisation of a strong alkali with a weak acid.
When we dissolve baking soda in water, an alkaline solution is obtained. This is because sodium bicarbonate dissociates in water to form two ions: ${ Na }^{ + }$ and ${ HC{ O }_{ 3 } }^{ - }$. Due to the addition of baking soda into the water, the water molecule ( ${ H }_{ 2 }O )$ also breaks into its constituent ions ${ H }^{ + }$ and ${ OH }^{ - }$. The ${ Na }^{ + }$ ions attracts the negatively charged ${ OH }^{ - }$ ions from water to form a strong alkali NaOH while the ${ HC{ O }_{ 3 } }^{ - }$ ions attract the positively charged ${ H }^{ + }$ions from water to form a weak acid ${ H }_{ 2 }{ CO }_{ 3 }$. This process is known as salt hydrolysis or hydrolysis of salt.
Let us examine the other options.
- ${ Na }_{ 2 }{ CO }_{ 3 }$ is the formula of sodium carbonate and it is commonly known as washing soda. It is used for washing purposes and it is white. Sodium bicarbonate is also soluble in water.
- ${ Na }_{ 2 }{ SO }_{ 4 }$ is the formula of sodium sulphate and it is also called sulphate of soda. It is a white powder that is soluble in water. It is a very cheap material and it is widely used as a filter in powdered home laundry detergents.
- NaCl is the formula of sodium chloride and it is known as common salt. Most of the salinity of the seawater is due to sodium chloride. The salt we eat daily is also sodium chloride. It is highly soluble in water and the pure form of this compound is colourless.

Note: Don’t confuse baking soda with washing soda. Though their name and formula are very similar they have one tiny difference. Washing soda has no hydrogen atom and it has two atoms of sodium while baking soda has a hydrogen atom and it contains only one sodium atom.
Baking soda: NaHC${O }_{ 3 }$
Washing soda: ${ Na }_{ 2 }{ CO }_{ 3 }$