Question

please answer both questions

QUESTION 10 What is the equilibrium hydronium ion concentration of an initially 4.5 M solution of hypoiodous acid, HOI, at 25°C (Ka - 2.3 x 10-11)? 1.4 x 10-5 M. 6.1.0 x 10.5M 43.2 10-6 M 72x10-6 M e 1.0~107M QUESTION 11 Which gives an acidic solution when dissolved in water? Na20 NH3 - NH4Br d. NaCN one of these

Answer 1

10)

HOI dissociates as:

HOI -----> H+ + IO-

4.5 0 0

4.5-x x x

Ka = [H+][IO-]/[HOI]

Ka = x*x/(c-x)

Assuming x can be ignored as compared to c

So, above expression becomes

Ka = x*x/(c)

so, x = sqrt (Ka*c)

x = sqrt ((2.3*10^-11)*4.5) = 1.017*10^-5

since c is much greater than x, our assumption is correct

so, x = 1.017*10^-5 M

So, [H+] = x = 1.0*10^-5 M

Answer: b

11)

a)

Na2O is metal oxide.

Metal oxides are basic in nature.

So, it is basic

b)

NH3 weak base

So, it is basic

c)

NH4Br is salt of weak base and Strong acid (HBr)

Only acid is strong

So, the salt NH4Br is acidic

d)

NaCN is salt of Strong base (NaOH) and weak acid

Only base is strong

So, the salt NaCN is basic

Answer: c