determine the molarity of a solution prepared by dissolving 11.5 g naoh to form 250.0 ml solution.

Explanation:

Step1: Calculate moles of NaOH

The molar - mass of NaOH is $M_{NaOH}=22.99 + 16.00+1.01=40.00\ g/mol$. The number of moles $n$ of NaOH is calculated using the formula $n=\frac{m}{M}$, where $m = 11.5\ g$ and $M = 40.00\ g/mol$. So, $n=\frac{11.5\ g}{40.00\ g/mol}=0.2875\ mol$.

Step2: Convert volume to liters

The volume $V$ of the solution is $V = 250.0\ mL$. Since $1\ L=1000\ mL$, then $V = 250.0\ mL\times\frac{1\ L}{1000\ mL}=0.2500\ L$.

Step3: Calculate molarity

Molarity $M$ is defined as $M=\frac{n}{V}$. Substituting $n = 0.2875\ mol$ and $V = 0.2500\ L$ into the formula, we get $M=\frac{0.2875\ mol}{0.2500\ L}=1.15\ mol/L$.

Answer:

$1.15$