Question

What volume of a 3.0 M HCl Solution be mixed with 500 mL of a 7 M HCl Solution to prepare a HCl Solution whose molarity will be 4.0?

Answer 1

Let V mL of 3.0 M HCl Solution is taken, then 

3 V + 500 x 7 = 4 x (500 + V) 

⟹ V = 1500 mL