Question

Consider a 1.00 L, 1.00 M solution of NaNO3. Will the concentration of NO3- decrease, stay the same, or increase if...

A) half of the solution is poured out?

B) 500 mL of water is added?

C) 500 mL of 1.00M NaNO3 is added?

D) 1.00 L of 0.500M NaNO3 is added?

E) 1.00 L of 1.00 M NaCl is added?

Please show work/explain reasoning

Answer 1

In solution NaNO3 ionizes as:

NaNO₃ <===> Na⁺ +   NO₃^-

As the concentration of solution is given 1M in 1 L, these ions would be uniform throughout the whole solution. So

A) concentration of NO3- would be same if half of the solution is poured out.

B) concentration of NO3- would change (here decrease because concentration of ions in solution is reciprocal of volume diluted by water and here total volume will increase after dilution with 500 mL water).

C) concentration of NO3- would not change even after addition of 500 mL of 1.00M NaNO3. Because this solution itself has the similar concentration (1.00M).

D) concentration of NO3- would change (decrease) after addition of 1.00 L of 0.500M NaNO3 because this solution has different concentration of NO3- and hence after mixing the resulting solution ahs less concentration of NO3^-.

E) concentration of NO3- would change (decrease) as concentration of Na+ is increasing only afrer addition of 1M NaCl solution. Here common ion is Na+ hence the equilibrium woud shift towards left to minimize the concentration of Na+ ion so it will take NO3- ions back.