NEET

Which of the following pK_a value represents the strongest acid ?

10^–4
10^–8
10^–5
10^–2

Solution

pK_a = –log K_a Smaller the value of pK_a, stronger will be acid
∴ Acid having pK_a value of 10^–8 is strongest acid.

At 25°C, the dissociation constant of a base, BOH, is 1.0 × 10¹². The concentration of hydroxyl ions in 0.01 M aqueous solution of the base would be

1.0 × 10^-5 mol L^-1
1.0 × 10^-6 mol L^-1
2.0 × 10^-6 mol L^-1
1.0 × 10^-7 mol L^-1

Solution

For the system : A(g) + 2B(g) ⟶ C(g)
the equilibrium concentration is A = 0.06 moles/l, B =0.12 moles/l C = 0.216 moles/l
The K_eq for the reaction is

250
416
4 × 10^–3
125

Solution

The pH of a weak mono acidic base, neutralized upto 80% with a strong acid in a dilute solution, is 7.40. The ionization constant of the base is –

1.0 × 10^-5
1.6 × 10^-7
1.0 × 10^-6
None of these

Solution

What will be the pH of a solution formed by mixing 50 ml of 0.5 M HCl solution and 150 ml of 0.5 M NaOH solution and 300 ml H₂O ?

13
12.7
7
11

Solution

The pH of a 10^–3 M HCl solution at 25°C if it is diluted 1000 times, will be–

3
zero
5.98
6.02

Solution

On dilution [H⁺] = 10^-6 M = 10^-6 mol
Now dissociation of water cannot be neglected,
Total [H⁺] = 10 – 6 + 10 –7 = 11 × 10^-7 pH = –log [H⁺]= –log(11 × 10^-7) = 5.98