Question

Baking soda mainly contains sodium bicarbonate. When this is treated with dilute hydrochloric acid, the following reaction occurs.
${\text{NaHC}}{{\text{O}}_{\text{3}}}{\text{ + HCl}} \to {\text{NaCl + C}}{{\text{O}}_{\text{2}}} \uparrow {\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}$
Answer the questions below.
1. What is the valency of sodium ions?
2. What is the valency of bicarbonate ions?
3. Is the chloride ion monovalent or divalent?
4. What do the symbols $\to$ and $\uparrow$ imply in the reaction?
5. If one more ${{\text{H}}^{\text{ + }}}$ion is removed from bicarbonate ion gives carbonate ion. Write the formula of the carbonate radical.
6. The bicarbonate ion is __________ anion.( Monatomic / Polyatomic)
7. Name the products formed in the above reaction
8. Identify the cation and the anion in the formula of Sodium chloride.
9. What is the difference between sodium and sodium ions?
10. State the law which must be fulfilled, while balancing the chemical equation.

Answer 1

The charge on the ion indicates its valency. Ions having valency one are known as a monovalent ion. Ions having valency two are known as a divalent ion. Ion containing only one atom is known as a monatomic ion. Ion containing more than two atoms is known as a polyatomic ion. Positively charged ions are known as cations and negatively charged ions are known as anions.

Complete answer:
We have given the reaction of baking soda with dilute hydrochloric acid.
${\text{NaHC}}{{\text{O}}_{\text{3}}}{\text{ + HCl}} \to {\text{NaCl + C}}{{\text{O}}_{\text{2}}} \uparrow {\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}$

1. The chemical formula of sodium ion is ${\text{N}}{{\text{a}}^{\text{ + }}}$.
The valency of the ion is nothing but the charge on the ion.
So, here we can say that the valency of sodium ion is 1 as it has a +1 charge.
Thus, the valency of sodium ion is 1.

2. The chemical formula of bicarbonate ion is ${\text{HC}}{{\text{O}}_{\text{3}}}^ -$.
As the charge on bicarbonate ion is -1 we can say that its valency is 1.
Thus, the valency of the bicarbonate ion is 1.

3. To determine whether the chloride ion is monovalent or divalent we have to determine its valency. Monovalent ions have valency 1 and divalent ions have valency 2.
The chemical formula of chloride ion is ${\text{C}}{{\text{l}}^{\text{ - }}}$.
From the chemical formula of chloride ion, we can say that chloride ion has a -1 charge. So, the valency of chloride ion is 1.
Thus, the chloride ion is monovalent.

4. The horizontal arrow ( $\to$) in the reaction indicates that the reaction is in progress.
The vertical arrow pointing up ($\uparrow$) indicates the gaseous state of the chemical species.

5. The chemical formula of bicarbonate ion is ${\text{HC}}{{\text{O}}_{\text{3}}}^ -$.
We have given that removal of one more ${{\text{H}}^{\text{ + }}}$ ion from bicarbonate ion gives carbonate ion. This indicates that carbonate ion does not contain any hydrogen atom and due to the removal of one, ${{\text{H}}^{\text{ + }}}$it has a -2 charge.
So, the formula of carbonate ion is ${\text{C}}{{\text{O}}_{\text{3}}}^{2 - }$.

6. To determine whether bicarbonate ion is monatomic or polyatomic ion we have to determine the number of atoms present in ion.
The prefix mono stands for one so ion-containing only one atom is known as a monoatomic ion.
The prefix poly stands for many so an ion containing more than two atoms is known as a polyatomic ion.
The bicarbonate ion (${\text{HC}}{{\text{O}}_{\text{3}}}^ -$) contains one hydrogen atom, one carbon atom and three oxygen atoms. As it contains a total 5 atoms so it is known as a polyatomic ion.
Thus, bicarbonate ions are polyatomic anions.

7. The reaction is: ${\text{NaHC}}{{\text{O}}_{\text{3}}}{\text{ + HCl}} \to {\text{NaCl + C}}{{\text{O}}_{\text{2}}} \uparrow {\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}$
Chemical species present on the right side of the horizontal arrow are the products of this reaction.
So, the products of these reactions are ${\text{NaCl,C}}{{\text{O}}_{\text{2}}}{\text{ and }}{{\text{H}}_{\text{2}}}{\text{O}}$.
The name of the product ${\text{NaCl}}$ is sodium chloride. The name of the product ${\text{C}}{{\text{O}}_{\text{2}}}$ is carbon dioxide gas. The name of the product ${{\text{H}}_{\text{2}}}{\text{O}}$ is water.

8. The formula of sodium chloride is ${\text{NaCl}}$. It contains ${\text{N}}{{\text{a}}^{\text{ + }}}$ ion and ${\text{C}}{{\text{l}}^{\text{ - }}}$ion. As we know that cation is a positively charged ion and anion is a negatively charged ion.
Thus, in the formula of sodium chloride, the cation is ${\text{N}}{{\text{a}}^{\text{ + }}}$ ion and anion is ${\text{C}}{{\text{l}}^{\text{ - }}}$ion.

9. Sodium is represented as ${\text{Na}}$ and sodium ion is represented as ${\text{N}}{{\text{a}}^{\text{ + }}}$.
Sodium is a neutral species so contains the same number of electrons as the atomic number. So, sodium has 11 electrons.
After the loss of one electron sodium is converted into sodium ion. Thus, sodium ions contain 10 electrons.
Thus, the difference between sodium and sodium ions is they contain 11 and 10 electrons respectively.

10. While balancing the chemical reaction Law of conservation of mass must be full fill. It states that mass is neither created nor destroyed in a chemical reaction.

Note:
Sodium bicarbonate reacts with hydrochloric acid and produces sodium chloride and carbonic acid. As carbonic acid is unstable it decomposes into carbon dioxide gas and water. To indicate gaseous species we use an arrow pointing up. To indicate solid species we use an arrow pointing down.