Given below are a few solutions and pH values. Match the solutions to the correct pH values. 

Why baking soda is used in the baking cake. Explain with the help of a balanced chemical equation. List down any other two use of baking soda.

                                                   (OR)

 

(i) Gauri had four solutions A, B, C, and D. She dipped pH paper into each solution and recorded the following observations.

Solution	Color of pH paper	pH of the solution
A	Green	7
B	Reddish-pink	2
C	Blue	10.5
D	Orange	6

a) Which of the samples has the lowest amount of Hydrogen ion concentration? 

b) Arrange the four samples in the increasing order of their pH.

(ii) When Plaster of Paris is mixed with water and applied on a fractured limb it becomes a hard mass. Explain with a balanced chemical equation.

(iii) Give anyone use of Plaster of Paris other than for correcting fractured limbs.

Solution:
a) Milk of magnesia: 10
b) Gastric juices: 1
c) Brine: 7
d) Aqueous Sodium hydroxide: 13
During the thermal decomposition of baking soda $\left(NaHC{O}_3\right),N{a}_{2}C{O}_3,C{O}_2$ and $H_{2}O$ is produced. The production  $C{O}_2$ gives the cake its fluffy and soft texture.
The balanced reaction is as follows:
$NaHC{O}_3\to N{a}_{2}C{O}_3+C{O}_2+H_{2}O$
Uses of baking soda are as follows:

1) It is used in fire extinguishers.
2) To neutralize the excess acid in the stomach, it acts as an antacid.
3) To neutralize the acidic effect of an insect sting. us

                                         (OR)

(i) 

(a) Sample C has the lowest amount of Hydrogen ion concentration.

$pH=-log\left[H^{+}\right]$

Since the value of pH is highest for sample C, it has the lowest amount of Hydrogen ion concentration.

(b) Increasing order of pH samples is are follows:

$B<D<A<C$

(ii) 

It is converted into Gypsum due to the moisture present in the atmosphere.

$CaS{O}_4\cdot \frac{1}{2}{H}_{2}O+\frac{3}{2}{H}_{2}O\to CaS{O}_4\cdot 2H_{2}O$

(Plaster of Paris)                              (Gypsum)

(iii)

Other uses of Plaster of Paris are as follows: 

1) It is used for making toys, dolls and statues. 

2) It is used in making decorative materials. 

3) It is used for plastering or smoothening of walls.