Question

which solution is the most concentrated?
○ 2.0 ml of 10 m h₂so₄, where h₂so₄ has a molar mass of 98 g/mol
○ 5.0 ml of 1.0 m pbso₄, where pbso₄ has a molar mass of 303 g/mol
○ 2.0 ml of 10.5 m h₂o₂, where h₂o₂ has a molar mass of 34 g/mol
○ 100 ml of 10 m nacl, where nacl has a molar mass of 58 g/mol

Explanation:

Step1: Recall Molarity Definition

Molarity ($M$) is moles of solute per liter of solution. Concentration is determined by molarity, not volume or molar mass.

Step2: Compare Molarities

• $\ce{H_2SO_4}$: $10$ M
• $\ce{PbSO_4}$: $1.0$ M
• $\ce{H_2O_2}$: $10.5$ M
• $\ce{NaCl}$: $10$ M

The highest molarity is $10.5$ M (for $\ce{H_2O_2}$), so this solution is most concentrated.

Answer:

2.0 mL of 10.5 M $\ce{H_2O_2}$, where $\ce{H_2O_2}$ has a molar mass of 34 g/mol