Question

How much water should be added to 200 cc of a semi normal solution of NaOH to make it exactly decinormal?
A. 1000 cc
B. 400 cc
C. 800 cc
D. 600 cc

Answer 1

Hint: Semi Normal Solution can be expressed as 1N solution. When 1/2-gram equivalent of the solute is dissolved in 1 litre of the solution it is called a semi-normal solution. it is denoted by N/2.

Complete answer:
When one-tenth gram equivalent mass of a substance is present in one litre of its solution then it is called decinormal solution. It is denoted by N/10 solution.
For any solution to be converted from one molarity to another or from one normality to another, use the formula \[{N_1}{V_1} = {N_2}{V_2}\]
Where \[{N_1}\] is initial normality. \[{N_2}\] is final normality. \[{V_1}\] is the initial volume. \[{V_2}\] is the final volume.
Formula Used: \[{N_1}{V_1} = {N_2}{V_2}\]
Semi-Normality (\[{N_1}\]) = 0.5 N
Volume (\[{V_1}\]) = 200 cc
Deci-Normality (\[{N_2}\]) = 0.1 N
Volume (\[{V_2}\]) =?
\[{N_1}{V_1} = {N_2}{V_2}\]
0.5 \[ \times \] 200 = 0.1 \[ \times \] \[{V_2}\]
\[{V_2}\]= \[\dfrac{{{\text{0}}{\text{.5 x 200}}}}{{{\text{0}}{\text{.1}}}}{\text{ = 1000cc}}\]
Volume of water added = (1000-200) = 800 cc

Hence option C is correct.

Note: Sodium hydroxide (NaOH) is a compound of ionic solids. It is a co-product of the processing of chlorines. It is crystalline solid in its pure form, colourless in nature. This compound is highly water-soluble, consisting of sodium cations and anions formed from hydroxide. NaOH absorbs airborne moisture. It is extremely corrosive and can cause eyes and other parts of the body to get extreme skin burning and irritations. This creates a high heat level and is thus often produced by adding the compound into the water, not the vice versa. This inorganic compound is used as a buffering agent in cosmetics. It can regulate the levels of PH, too. Sodium chloride has a PH of 13.
Sodium hydroxide is a crystalline solid of pure, transparent nature. Because of its corrosive effect on many things, it decomposes proteins at room temperatures and can cause chemical burning of human bodies, it is widely referred to as caustic soda. Although it does not occur in nature, sodium hydroxide has been made from readily obtainable raw material on a wide scale for many years, and is used in various industrial processes.