Question

Following solutions were prepared by mixing different volumes of NaOH of HCl different concentrations.

pH of which one of them wilt be equal to 1? 

(a) (iv) 

(b) (i) 

(c) (ii) 

(d) (iii)

Answer 1

(d)

No of moles of HCl = 0.2 x 75 x 10^-3 = 15 x 10^-3

No of moles of NaOH = 0.2 x 25 x 10^-3 = 5 x 10^-3

No of moles of HCl after mixing = 15 x 10^-3 – 5 x 10^-3

∴ Concentration of HCl = \(\frac{No.\,of\,mol\,of\,HCl}{Vol\,in\,litre}\) = \(\frac{10\times10^{-3}}{100\times10^{-3}}\) = 0.1 M

for (iii) solution, pH of 0.1 M HCI = – 1og₁₀ (0.1) = 1