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's 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, oxidation number of P is +5

(b) NaHSO_{4}

Let's 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, oxidation number of S is +6

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

Let's 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's 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's 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's 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's 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's 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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^{–31}kg. If its K.E. is 3.0 × 10^{–25}J, calculate its wavelength. - Q:-
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:-
What will be the minimum pressure required to compress 500 dm

^{3}of air at 1 bar to 200 dm^{3}at 30°C? - Q:-
In a process, 701 J of heat is absorbed by a system and 394 J ofwork is done by the system. What is the change in internal energy for the process?

- 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:-
Which one of the following will have largest number of atoms?

(i) 1 g Au (s)

(ii) 1 g Na (s)

(iii) 1 g Li (s)

(iv) 1 g of Cl2(g)

- Q:-
At 0°C, the density of a certain oxide of a gas at 2 bar is same as that of dinitrogen at 5 bar. What is the molecular mass of the oxide?

- 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:-
What do you understand by bond pairs and lone pairs of electrons? Illustrate by giving one example of each type.

- Q:-
Calculate the mass percent of different elements present in sodium sulphate (Na

_{2}SO_{4}). - Q:-
Calculate the total pressure in a mixture of 8 g of dioxygen and 4 g of dihydrogen confined in a vessel of 1 dm

^{3}at 27°C. R = 0.083 bar dm^{3}K^{–1}mol^{–1.} - Q:-
A 0.02 M solution of pyridinium hydrochloride has pH = 3.44. Calculate the ionization constant of pyridine

- Q:-
Classify the following reactions in one of the reaction type studied in this unit.

(a) CH

_{3}CH_{2}Br + HS- → CH_{3}CH_{2}SH + Br-(b) (CH

_{3})_{2}C = CH_{2}+ HCl → (CH_{3})_{2}ClC-CH_{3}(c) CH

_{3}CH_{2}Br + HO- → CH_{2}= CH_{2}+ H_{2}O + Br-(d) (CH

_{3})_{3}C - CH_{2}OH + HBr → (CH_{3})_{2}CBrCH_{2}CH_{3}+ H_{2}O - Q:-
Which hybrid orbitals are used by carbon atoms in the following molecules?

(a)CH

_{3}–CH_{3};(b) CH

_{3}–CH=CH_{2};(c) CH

_{3}-CH_{2}-OH;(d) CH

_{3}-CHO(e) CH

_{3}COOH - Q:-
Convert the following into basic units:

(i) 28.7 pm

(ii) 15.15 pm

(iii) 25365 mg

- Q:-
Which of the following statements related to the modern periodic table is incorrect?

(a) The p-block has 6 columns, because a maximum of 6 electrons can occupy all the orbitals in a p-shell.

(b) The d-block has 8 columns, because a maximum of 8 electrons can occupy all the orbitals in a d-subshell.

(c) Each block contains a number of columns equal to the number of electrons that can occupy that subshell.

(d) The block indicates value of azimuthal quantum number (l ) for the last subshell that received electrons in building up the electronic configuration. - Q:-
Explain the difference in properties of diamond and graphite on the basis of their structures.

- 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}

Linju
2019-11-26 21:15:16

Gud to disclose all the answers .anyway thanks

- NCERT Chapter