Answer:
[Cl⁻] = 1,5x10⁻⁴M
Explanation:
First of all, let's determinate the mole of each salt.
Molarity . volume = Mole
Volume must be in L, cause molarity is mol/L
NaCl → Na⁺ + Cl⁻
Ratio is 1:1
0.15 mol/L . 0.025L = 3.75x10⁻³ mole
As ratio is 1:1, from 3.75x10⁻³ mole of salt, I have 3.75x10⁻³ mole of chloride
CaCl₂ → Ca²⁺ + 2Cl⁻
Ratio is 1:2 so, from 1 mol of salt I'll get the double of mole of chloride
0.075 mol/L . 0.010 L = 7.5x10⁻⁴ mol
7.5x10⁻⁴ mol . 2 = 1.5x10⁻³ mole
Total mole of Cl⁻: 3.75x10⁻³ + 1.5x10⁻³ = 5.25x10⁻³
This 5.25x10⁻³ mole are present in a total volume of 35 mL.
Let's convert 35 mL in L → 0.035L (35/1000)
Molarity is mol/L → 5.25x10⁻³ mol / 0.035L = 1,5x10⁻⁴M
