Question

1.What is the pH of 0.15 M HI and the pH of 0.15 M H₂S?

2. An example of P in its maximum and minimum oxidation states is:

a)white phosphorus and red phosphorus

b)P₄O₁₀ and PH₃

c)H₃PO₄ and Na₃PO₄

d)PH₃ and Na₃P

3.Match the following statements in Column A with the correct answer from Column B

A B

            Formed when hydrochloric acid reacts with sodium hydroxide O₂

            Formed when potassium peroxide is heated                                       N₂

            Formed when ammonium chloride is heated                                       Cl₂

            Formed when calcium hypochlorite reacts with HCl                         CH₃COOH

            Formed when sodium oxide reacts with water                                   HCl

                                                                                                                        H₂                   

                                                                                                                        NaOH

                                                                                                                        NaCl

Answer 1

1) pH of 0.15 M HI :

[H+] = 0.15 N (For monoprotic acids, Molarity and normality are equal)

pH = -log [H+]

= - log [0.15]

= 0.823

pH = 0.823

pH of 0.15 M H2S

[H+] = 0.15 M = 0.15x 2 N = 0.30 N ( For diprotic acids, Normality = Molarity x 2)

pH = -log [H+]

= - log [0.30]

= 0.522

pH = 0.522

2)

An example of P in its maximum and minimum oxidation states is:

a)white phosphorus and red phosphorus   b)P4O10 and PH3 c)H3PO4 and Na3PO4   d)PH3 and Na3P

Ans : b

Maximum oxidation state of P is +5 and minimum oxidation state is -3.

a) white phosphorus and red phosphorus

In both, oxidation state of P = 0

b) P4O10 and PH3

P4O10 : 4P+ 10 (-2) = 0

P = +5

PH3 : P + 3(+1) = 0

P = -3

c) H3PO4 and Na3PO4

  H3PO4 : 3(+1) + P + 4(-2) = 0

P = +5

Na3PO4 :

3(+1) + P + 4(-2) = 0

P = +5

d) PH3 and Na3P

PH3 : P + 3(+1) = 0

P = -3

Na3P : 3(+1) + P = 0

P = -3

3) a) when hydrochloric acid reacts with sodium hydroxide = NaCl will be formed

HCl + NaOH ----------> NaCl + H2O

b) when potassium peroxide is heated = O2 will be formed

2 K2O2 ------> 2 K2O + O2

c) when ammonium chloride is heated = HCl will be formed

NH4Cl -------------> NH3+HCl

d) when calcium hypochlorite reacts with HCl = Cl2 wil be formed

Ca(OCl)2 + 4 HCl ------------------> CaCl2 + 2 H2O + 2 Cl2

e)when sodium oxide reacts with water = NaOH will be formed.

Na2O + H2O -------------> 2 NaOH