Question

Number of $H^{+}$ ions present in $250mL$ of lemon juice of $pH=3$ is :

• A. $1.506\times {10}^{22}$
• B. $1.506\times {10}^{23}$
• C. $1.506\times {10}^{20}$
• D. $3.012\times {10}^{21}$
• E. $2.008\times {10}^{23}$

Answer 1

Answer: (C)

$1.506\times {10}^{20}$

$pH=3$ so $H^{+}={10}^{-3}M$ means ${10}^{-3}$ moles of $H^{+}$ are present in 1000 mL of solution.

Number of moles of $H^{+}$ ions in $250mL=\frac{{10}^{-3}}{1000}$= $0.25\times {10}^{-3}.$

Number of moles of $H^{+}$ ions in $250mL=0.25\times {10}^{-3}\times 6.023\times {10}^{23}=1.506\times {10}^{20}.$