Question

Which of the following solutions will have pH close to 1.0?

• A. $100mL,0.1MHC$l + $100mL,0.1MNaOH$
• B. $55mL,0.1MHCl$+ $45mL,0.1MNaOH$
• C. $10mL,0.1MHCl$ + $90mL,0.1MNaOH$
• D. $75mL,0.2MHCl$ + $25mL,0.2MNaOH$

Answer 1

The correct option is D $75mL,0.2MHCl$ + $25mL,0.2MNaOH$

For a monoprotic acid Normality = Molarity

$N=\frac{N_A{V}_A-N_B{V}_B}{V_A+V_B}=\frac{75\times 0.2-25\times 0.2}{100}=\frac{15-5}{100}=0.1N$

$\therefore \left[H^{+}\right]=0.1$

$pH=-lo{g}_{10}\left[H^{+}\right]$

$\therefore pH=1$

75ml 0.2M HCl + 25ml 0.2M NaOH have a pH close to 1.0