Question 1

Assign oxidation number to the underlined elements in each of the following species:

(a) NaH_{2}PO_{4}

(b) NaHSO_{4}

(c) H_{4}P_{2}O_{7}

(d) K_{2}MnO_{4}

(e) CaO_{2}

(f) NaBH_{4}

(g) H_{2}S_{2}O_{7}

(h) KAl(SO_{4})_{2}.12 H_{2}O

Answer

(a) NaH_{2}PO_{4}

Let assume oxidation number of P is x.

We know that,

Oxidation number of Na = +1

Oxidation number of H = +1

Oxidation number of O = -2

Then we have

1(+1) + 2(+1) + 1 (x) + 4(-2) = 0

⇒ 1 + 2 + x - 8 = 0

⇒ x - 5 = 0

⇒ x = + 5

Hence the oxidation number of P is +5

(b) NaHSO_{4}

Let assume oxidation number of S is x.

Oxidation number of Na = +1

Oxidation number of H = +1

Oxidation number of O = -2

Then we have:

1(+1) + 1(+1) + 1 (x) + 4(-2) = 0

⇒ 1 + 1 + x - 8 = 0

⇒ x-6 = 0

⇒ x = +6

Hence the oxidation number of S is +6

(c) H_{4}P_{2}O_{7}

Let assume oxidation number of P is x.

Oxidation number of H = +1

Oxidation number of O = -2

Then we have:

4(+1) + 2(x) + 7 (-2) = 0

⇒ 4 + 2x - 14 = 0

⇒ 2x - 10 = 0

⇒ 2x = +10

⇒ x = +5

Hence, Oxidation number of P is +5

(d) K_{2}MnO_{4}

Let assume oxidation number of Mn is x.

Oxidation number of K = +1

Oxidation number of O = -2

Then we have:

2(+1) + 1(x) + 4 (-2) = 0

⇒ 2 + x - 8 = 0

⇒ x - 6 = 0

⇒ x = +6

Hence, Oxidation number of Mn is +6

(e) CaO_{2}

Let assume oxidation number of O is x.

Oxidation number of Ca = +2

Then we have:

1(+2) + 2(x) = 0

⇒ 2 + 2x = 0

⇒ 2x = -2

⇒ x = -1

Hence, Oxidation number of O is -1

(f) NaBH_{4}

Let assume oxidation number of B is x.

Oxidation number of Na = +1

Oxidation number of H = -1

Then we have:

1(+1) + 1(x) + 4(-1) = 0

⇒ 1 + x -4 = 0

⇒ x - 3 = 0

⇒ x = +3

Hence, Oxidation number of B is +3.

(g) H_{2}S_{2}O_{7}

Let assume oxidation number of S is x.

Oxidation number of O = -2

Oxidation number of H = +1

Then we have:

2(+1) + 2(x) + 7(-2) = 0

⇒ 2 + 2x - 14 = 0

⇒ 2x - 12 = 0

⇒ x = +6

Hence, Oxidation number of S is +6.

(h) KAl(SO_{4})_{2}.12 H_{2}O

Let assume oxidation number of S is x.

Oxidation number of K = +1

Oxidation number of Al = +3

Oxidation number of O = -2

Oxidation number of H = +1

Then we have:

1(+1) + 1 (+3) + 2(x) + 8(-2) + 24(+1) + 12 (-2) = 0

⇒ 1 + 3 + 2x -16 +24 -24 = 0

⇒ 2x - 12 = 0

⇒ 2x = +12

⇒ x = +6

Hence, Oxidation number of S is +6.

- Q:-
Calculate the amount of carbon dioxide that could be produced when

(i) 1 mole of carbon is burnt in air.

(ii) 1 mole of carbon is burnt in 16 g of dioxygen.

(iii) 2 moles of carbon are burnt in 16 g of dioxygen.

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Calculate the wavelength of an electron moving with a velocity of 2.05 × 10

^{7}ms^{–1}. - Q:-
Balance the following redox reactions by ion – electron method :

(a) MnO

_{4 }^{– }(aq) + I^{ – }(aq) → MnO_{2 (s)}+ I_{2(s)}(in basic medium)(b) MnO

_{4}^{–}(aq) + SO_{2 (g) }→ Mn^{2+}(aq) + HSO_{4}^{–}(aq) (in acidic solution)(c) H

_{2}O_{2 (aq)}+ Fe^{2+ }(aq) → Fe^{3+}(aq) + H_{2}O (l) (in acidic solution)(d) Cr

_{2}O_{7}^{2–}+ SO_{2(g)}→ Cr^{3+}_{(aq)}+ SO_{4}^{2– }(aq) (in acidic solution) - Q:-
Determine the empirical formula of an oxide of iron which has 69.9% iron and 30.1% dioxygen by mass.

- Q:-
In a reaction A + B2 → AB2 Identify the limiting reagent, if any, in the following reaction mixtures.

(i) 300 atoms of A + 200 molecules of B

(ii) 2 mol A + 3 mol B

(iii) 100 atoms of A + 100 molecules of B

(iv) 5 mol A + 2.5 mol B

(v) 2.5 mol A + 5 mol B

- Q:-
Calcium carbonate reacts with aqueous HCl to give CaCl

_{2}and CO_{2}according to the reaction,CaCO

_{3(s)}+ 2 HCl_{(aq)}→ CaCl_{2(aq)}+ CO_{2(g)}+ H_{2}O_{(l)}What mass of CaCO

_{3}is required to react completely with 25 mL of 0.75 M HCl? - Q:-
Density of a gas is found to be 5.46 g/dm

^{3}at 27 °C at 2 bar pressure. What will be its density at STP? - Q:-
A sample of drinking water was found to be severely contaminated with chloroform, CHCl

_{3}, supposed to be carcinogenic in nature. The level of contamination was 15 ppm (by mass).(i) Express this in percent by mass.

(ii) Determine the molality of chloroform in the water sample.

- Q:-
Calculate the mass of sodium acetate (CH

_{3}COONa) required to make 500 mL of 0.375 molar aqueous solution. Molar mass of sodium acetate is 82.0245 g mol^{–1}

- Q:-
Addition of HBr to propene yields 2-bromopropane, while in the presence of benzoyl peroxide, the same reaction yields 1-bromopropane. Explain and give mechanism.

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What would be the SI unit for the quantity

*pV*^{2}*T*^{2}/*n?* - Q:-
Calculate the standard enthalpy of formation of CH

_{3}OH(l) from the following data:CH

_{3}OH (l) + 3/2 O_{2}(g) → CO_{2}(g) + 2H_{2}O(l) ; Δ_{r}H^{0 }= –726 kJ mol^{–1}C(g) + O

_{2}(g) → CO_{2}(g) ; Δ_{c}H^{0}= –393 kJ mol^{–1}H

_{2}(g) + 1/2 O_{2}(g) → H_{2}O(l) ; Δ_{f}H^{0}= –286 kJ mol^{–1}. - Q:-
It has been found that the pH of a 0.01M solution of an organic acid is 4.15. Calculate the concentration of the anion, the ionization constant of the acid and its pK

_{a}. - Q:-
At 473 K, equilibrium constant K

_{c }for decomposition of phosphorus pentachloride, PCl_{5}is 8.3 ×10^{-3}. If decomposition is depicted as,PCl

_{5}(g)**↔**PCl_{3}(g) + Cl_{2}(g) Δ_{r}H^{0}= 124.0 kJ mol^{–1}(a) write an expression for Kc for the reaction.

(b) what is the value of Kc for the reverse reaction at the same temperature ?

(c) what would be the effect on K

_{c}if (i) more PCl5 is added (ii) pressure is increased (iii) the temperature is increased ? - Q:-
Write bond line formulas for : Isopropyl alcohol, 2,3-Dimethyl butanal, Heptan-4- one.

- Q:-
Draw the resonance structures for the following compounds. Show the electron shift using curved-arrow notation.

(a) C

_{6}H_{5}OH(b) C

_{6}H_{5}NO_{2}(c) CH

_{3}CH=CHCHO(d) C

_{6}H_{5}–CHO(e) C

_{6}H_{5}- C^{+}H_{2}(f) CH

_{3}CH = CHC^{+}H_{2} - Q:-
Justify that the following reactions are redox reactions:

(a) CuO

_{(s)}+ H_{2(g)}→ Cu_{(s) }+ H_{2}O_{(g)}(b) Fe

_{2}O_{3(s)}+ 3CO_{(g) }→ 2Fe_{(s)}+ 3CO_{2(g) }(c) 4BCl

_{3(g)}+ 3LiAlH_{4(s)}→ 2B_{2}H_{6(g) }+ 3LiCl_{(s) }+ 3 AlCl_{3 (s) }(d) 2K

_{(s) }+ F_{2(g)}→ 2K^{+}F^{– }_{(s)}(e) 4 NH

_{3(g)}+ 5 O_{2(g) }→ 4NO_{(g) }+ 6H_{2}O_{(g)} - Q:-
What is meant by the term bond order? Calculate the bond order of: N

_{2}, O_{2},O_{2}^{+},and O_{2}^{-}. - Q:-
Calculate the temperature of 4.0 mol of a gas occupying 5 dm

^{3 }at 3.32 bar.(R = 0.083 bar dm

^{3}K^{–1}mol^{–1}).

Linju
2019-11-26 21:15:16

Gud to disclose all the answers .anyway thanks

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