Question

The molarity of $NO_3^-$ in the solution after $2L$ of $3M \, AgNO_3$ is mixed with $3L$ of $1M \, BaCl_2$ is

• A. 1.2 M
• B. 1.8 M
• C. 0.5 M
• D. 0.4 M

Answer 1

Answer: (A)

1.2 M

Answer 2

$2\,L$ of $3M \, AgNO_3$ will contains $6$ moles of $AgNO_3$.
$3\,L$ of $1 \, M \, BaCl_2$ will contain $3$ moles of $BaCl_2$.
${2AgNO_3 + BaCl_2 \to2AgCl + Ba(NO_3)_2. }$
So, 6 moles of $AgNO_3$ will react with 3 moles on $BaCl_2$ it means, two solution will react completely to form 3 moles of $Ba(NO_3)_2 \equiv$ 6 moles of $NO_3^-$ ions in $2+35L$ solution
Hence, molarity of $NO_3^- = \frac{6}{5} = 1.2 \, M$