The hydrogen ion concentration of a 10^-8 M HCL aqueous solution at 298 K (K_w = 10^-14) is:

• 1.0 x 10^-6

• 1.0525 x 10^-7 M

• 9.525 x 10^-8 M

• 9.525 x 10^-8 M

B.

1.0525 x 10^-7 M

In aqueous solution of 10^-8 M HCl, [H⁺] is based upon the concentration of H⁺ ion of 10^-8 M HCl and concentration of H⁺ ion of water K_w of H₂O = 10^-14 = [H⁺][OH^-] or [H⁺] = 10^-7 M (due to neutral behaviour) os, in aqueous solution of 10^-8 M HCl,
[H⁺] = [H⁺] of HCl +[H⁺] of water

= 10^-8 + 10^-7 = 11 x 10^-8 M
1.10 x 10^-7 M

C.

Every AB₅ molecules does, in fact, have square pyramid structure

Every AB₅ molecule does not, in fact, have square pyramidal structure but AB₅ molecules have trigonal bipyramidal structures due to sp³d hybridisation.

C.

HgI₄^3-, I₃^-

In a solution containing HgCl₂, I₂ and I–, both HgCl₂ and I₂
compete for I^–.
Since formation constant of [HgI₄]^2– is 1.9 × 10³⁰
which is very large as compared with I₃^– (K_f= 700)
therefore, I^– will preferentially combine with HgCl₂
HgCl₂ + 2l^- → Hgl₂↓ + 2Cl^-
Hgl₂ + 2l^- → [Hgl₄]2^-

C.

${\mathrm{C}}_6{\mathrm{H}}_5 -\stackrel{+}{\mathrm{C}}-{\mathrm{C}}_6{\mathrm{H}}_5$

Due to more possibility for delocalisation in 

$$\begin{gathered} {\mathrm{C}}_6{\mathrm{H}}_5 - \stackrel{+}{\mathrm{C}} -{\mathrm{C}}_6{\mathrm{H}}_5 (\mathrm{of} \mathrm{\pi } -\mathrm{electrons}), \\ {\mathrm{C}}_6{\mathrm{H}}_5 \mathrm{\_}\stackrel{+}{\mathrm{C}} -{\mathrm{C}}_6{\mathrm{H}}_5 \mathrm{is} \mathrm{the} \mathrm{most} \mathrm{stable} \mathrm{ion}. \end{gathered}$$

B.

pH > 7

n_HCl = M_HCl x V_HCl and n_NaOH = M_NaOH x V_NaOH

where n = number of moles

M = molarity, V = volume

∴ n_HCl  = 0.5 x 750 = 375 milimoles

n_NaOH = 2.0 x 250 = 500 milimoles

∵ n_NaOH > n_HCl

The solution is basic and has pH > 7