Question

For $40$ grams of sodium hydroxide is dissolved in $90$ grams of water. Then, mole fraction of sodium hydroxide is:

a) $0.1g$

b) $0.30g$

c) $0.434g$

d) $0.266g$

Answer 1

We will firstly discuss the sodium hydroxide that it is . It is a white solid ionic compound that contains sodium ions as well as the hydroxide ions. Moreover it is insoluble in ether and other non-polar solvents. Then the mole fraction is calculated as $=$ number of molecules of component/total molecules present.

Complete step by step answer:

Here in the question we are talking about sodium hydroxide. So it is basically the caustic soda that we call in daily language further chemically it can be written as NaOH. It is a white solid ionic compound that contains sodium ions as well as the hydroxide ions. Moreover it is insoluble in ether and other non-polar solvents.

Then in the question we need to find the mole fraction. So we can say that the mole fraction helps in determining the number of molecules of a particular component in the given mixture. It is further found out by writing the number of molecules of a particular component and further dividing it by the total number of moles in the given mixture. It is also represented by the X. moreover it helps in determining the concentration of the solution.

Further it can be solved as we are given $40$ grams of sodium hydroxide is dissolved in $90$ grams of water.

Then the mole fraction is calculated as $=$ number of molecules of component/total molecules present.

No. of moles NaOH $=\dfrac{\text{mass of NaOH}}{\text{molar mass of NaOH}}$

$= \dfrac{40}{40}$

$= 1$

No. of moles Water $=\dfrac{\text{mass of water}}{\text{molar mass of water}}$

$= \dfrac{90}{18}$

$= 5$

Mole fraction of NaOH $= \dfrac{\text{No. of moles of NaOH}}{\text{No. of moles of NaOH + No. of moles of water}}$

$=\dfrac{1}{1+5}$

$=\dfrac{1}{6}$

$=0.16g$

Therefore, the mole fraction of sodium hydroxide is found to be $0.16g$.

Hence the correct option is Option A.

Note:
We must know that sodium hydroxide has several uses such as used in the manufacture of salts and detergents, used for increasing alkalinity, used in petroleum industry, used in caustic washing and many more.