Question

\(4\) g of NaOH is dissolved in \(1.0\) L solution. The pH of solution is

• A. \(13\)
• B. \(1\)
• C. \(12\)
• D. \(7.4\)

Hint:

For strong bases, first find \(pOH\), then use \(pH=14-pOH\).

Answer 1

The Correct Option is A

Step 1: Molecular weight of NaOH is: \[ 23+16+1=40 \]

Step 2: Number of moles of NaOH: \[ \text{Moles}=\frac{4}{40}=0.1 \]

Step 3: Volume of solution: \[ 1.0\,L \]

Step 4: Molarity of NaOH: \[ M=\frac{0.1}{1}=0.1\,M \]

Step 5: NaOH is a strong base, so: \[ [OH^-]=0.1=10^{-1} \]

Step 6: Calculate pOH: \[ pOH=-\log[OH^-] \] \[ pOH=-\log(10^{-1})=1 \]

Step 7: Use: \[ pH+pOH=14 \] \[ pH=14-1=13 \] \[ \boxed{13} \]