Answer:
4.1 mol·L⁻¹
Explanation:
You are diluting the solution with water, so you can use the dilution formula
c₁V₁ = c₂V₂ Divide each side by V₂
c₂ = c₁ × V₁/V₂
Data:
c₁ = 7.0 mol·L⁻¹; V₁ = 2.5 L
Water added = 1.5 L
Calculations:
(a) New volume
V₂ = 2.5 L + 1.8 L
= 4.3 L
(b) New concentration
c₂ = 7.0 × 2.5/4.3
= 7.0 × 0.581
= 4.1 mol·L⁻¹