Question

If 5.0 milliliters of a 0.20 M HCl solution is required to neutralize exactly10. milliliters of NaOH, what is the concentration of the base?(1) 0.10 M (3) 0.30 M(2) 0.20 M (4) 0.40 M

Answer 1

The answer is (1) 0.1 M NaOH

Answer 2

NaOH+ HCl -> NaCl+ H2O
Based on the above balanced equation, we know that 1 mol HCl= 1 mol NaOH (keep it in mind; it will be used later)

We know that 0.20M HCl solution (soln)= 0.20mol HCl/1L HCl soln (this one is based on the definition of molarity).

First, we have to find the mole of HCl:
5.0mL HCl solution* (1L soln/ 1,000mL soln)* (0.20mol HCl/1L HCl soln)= 1.0*10^(-3)mol HCl.

Now that we know the mole of HCl, let's find the molarity of NaOH:
1.0*10^(-3)mol HCl* (1mol NaOH/1 mol HCl)* (1/10.mL NaOH soln)* (1,000mL NaOH soln/1L NaOH soln)= 0.10mol/L NaOH soln = 0.10M NaOH soln

Hope this would help :))