Question

8 gram NAOH dissolves in 250 ml solution. this solution is diluted in 500 ml water. find the molarity in dilute solution . also find moles of NAOH
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Answer 1

Final answer:

Molarity of $NaOH$ is $0.267 M$

Number of moles of $NaOH$ is 0.2 $mol$

Given that: We are given $8$ $g$ $NaOH$ dissolves in $250$ $mL$ solution, this solution is diluted in $500$ $mL$ water.

To find: We have to find molarity of $NaOH$ in dilute solution and number of moles of $NaOH$.

Explanation:

• Molarity (M) of solution is defined as the number of mole of solute that dissolved in one litre of the solution.

So $molarity, M = \frac{Number of mole of solute}{Volume of solution in litre}$

• $Molarity of NaOH= \frac{Number of mole of NaOH}{Volume of solution in litre}$

$Number of moles= \frac{Given mass (g)}{Molar mass}$

• $Number of moles of NaOH= \frac{Given mass of NaOH(g)}{Molar mass of NaOH}$

Molar mass of $NaOH$ = $40 \frac{g}{mol}$

Given mass of $NaOH$= 8 g

• Number of moles of $NaOH$ = $\frac{8g}{40(\frac{g}{mol})} = 0.2 mol$

• Given that $8$ $g$ $NaOH$ dissolves in $250$ $mL$ solution and this solution is diluted in $500$ $mL$ water.

So final volume = $250mL+ 500mL=750mL= 0.75L$

• Number of moles of $NaOH$ is same.

• Molarity of $NaOH$ = $\frac{0.2 mol}{0.75L}= 0.267 M$

• Number of moles of a substance is the ratio of given mass of that substance to the molar mass of same substance.

• We already calculate the number of moles of $NaOH$

Number of moles of $NaOH$ is $0.2$ $mol$

• Hence,

Molarity of $NaOH$ is $0.267 M$

Number of moles of $NaOH$ is $0.2$ $mol$

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