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# The worth of the solubility unit (K

The worth of the solubility unit (K

Question step 3. The solubility of BaSOcuatro in water is dos.42 x ten -3 gL -1 at 298K. sp) will be ………………….. (Given molar mass of BaSO4 = 233g mol -1 ) (a) 1.08 x 10 -14 mol 2 L 2 (b) 1.08 x 10 -12 mol 2 L 2 (c) 1.08 x 10 -10 mol 2 L 2 (d) 1.08 x 10 -8 mol 2 L -2 Answer: (c) 1.08 x 10 -10 mol 2 L 2 BaSO4 \(\rightleftharpoons\) Ba 2+ + SO4 2- Ksp = (s) (s) Ksp = (s) 2

Question 4. pH of a saturated solution of Ca(OH)2 is 9. The Solubility product (K) of Ca(OH)2 ……………….. (a) 0.5 x 10 -15 (b) 0.25 x 10 -10 (c) 0.125 x 10 -15 (d) 0.5 x 10 -10 Answer: (a) 0.5 x 10 -15 Ca(OH)2 \(\rightleftharpoons\) Ca 2+ + 2OH – Given that pH = 9 pOH = 14 – 9 = 5 [p0K = – 1og10[OH – ]] [OH – ] = 10 -pOH [OH – ] =10 -5 M Ksp = [Ca 2+ ] [OH – ] 2

Question 5. Conjugate base for bronsted acids H2O and HF are ……………… (a) OH – and H2FH + , respectively (b) H3O + and F – , respectively (c) OH – and F – , respectively (d) H3O + and H2F + , respectively Answer: (c) OH – and F – , respectively

Question 6. Which will make basic buffer? (a) 50 mL of 0.1M NaOH + 25mL of 01M CH3COOH (b) 100 mL of 0.1M CH3COOH + 100 mL of 0.1M NH4OH (c) 100 mL of 0.1M HCI + 200 mL of 0.1M NH4OH (d) 100 mL of 0.1M HCI + 100 mL of O.1 M NaOH Answer: (c) 100 mL of 0.1M HCI + 200 mL of 0.1M NH4OH Basic buffer is the solution which has weak base and its salt