Question

10 pts) A student titrates a 20.00 mL sample of an aqueous borax solution with 1.03 M H2SO4. If 2.07 mL of acid are needed to reach the equivalence point, then what is the molarity of the borax solution

Answer 1

Answer: The molarity of the borax solution is 0.107 M

Explanation:

The neutralization reaction is:

$Na_2B_4O_7.10H_2O+H_2SO_4(aq)\rightarrow Na_2SO_4+4H_3BO_3+5H_2O$

According to neutralization law:

$n_1M_1V_1=n_2M_2V_2$

where,

$n_1$ = basicity of $H_2SO_4$ = 2

$n_2$ = acidity of borax = 2

$M_1$ = concentration of $H_2SO_4$ = 1.03 M

$M_2$ = concentration of borax =?

$V_1$ = volume of $H_2SO_4$  = 2.07ml

$V_2$ = volume of borax = 20.0 ml

Now put all the given values in the above law, we get the molarity of borax:

$(2\times 1.03\times 2.07)=(2\times M_2\times 20.0)$

By solving the terms, we get :

$M_2=0.107M$

Thus the molarity of the borax solution is 0.107 M