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Mole in Terms of Molar Volume
Theory Questions and Answers

The volume occupied by a gas at standard temperature and pressure (S.T.P) is referred to as molar volume of a gas or ga...

 

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Question 1

Calculate the number of moles present the following substances (a) 7.1g of chlorine gas (Cl2g) (b) 2.7g of Aluminium (Al) (c) 7.15g of Potassium Chloride (KCl) (Cl = 35.5, Al = 27, K = 39)

(a) 7.1g of chlorine gas

Answer – 

7.1g of Cl2(g).

no of moles = \( \frac{mass}{molar\;mass} \)

m.m of Cl2  = 35.5 x 2 = 71 mol

n = \( \frac{7.1}{71} \) = 0.1g

(b) 2.7g of Aluminium (Al)

Answer – 

n = \( \frac{2.7}{27} \)

n = 0.1g

(c) 7.15g of Potassium Chloride (KCl)

Answer – 

m.m of KCL = 39 + 35.5 ⇒ 74.5

n = \( \frac{7.15}{74.5} \)

n = 0.1g

Question 2

Calculate the mass of substance present in the following (a) 1 mole of sodium hydroxide (NaOH) (b) 0.001 mole of Lead (II) trioxonitrate(V) Pb(NO3)2 (c) 2 moles of oxygen gas (O2 ). (Na = 23, O = 16, H = 1, Pb = 207, N = 14)

(a) 1 mole of sodium hydroxide (NaOH)

Answer – 

1mole of NaOH

No of moles = \( \frac {mass}{molar\;mass}\)

Mass of substance = no of moles x molar molar mass

m.m of NaOH = 23 + 16 + 1 ⇒ \( \frac{40g}{mol}\)  

m = 0.001mole x 40gmol-1

m = 40g

 

(b) 0.001 mole of Lead (II) trioxonitrate(V) Pb(NO3)2

Answer –

0.001mole of Pb(NO3)2

m.m of Pb(NO3)2 = 207 + 14×2 + 16x3x2

= 207 + 28 + 96

= 331gmol-1

m = 0.001mole x 331gmol-1

= 0.331g. 

 

(c) 2 moles of oxygen gas (O2)

Answer –

2moles of O2(g).

m.m of O2 = 16×2 = 32.gmol-1

m = 2mol x 32gmol-1

= 64g.

Question 3

Calculate the number of particles present in the following substances (a) 1.5moles of Hydrogen chloride gas (HCl) (b) 3 moles of sodium trioxonitrate (V) (NaNO3) (c) 0.2 moles of Lead (II) Chloride (PbCl2). Avogadro’s Number = 6.02 x 1023

 

(a) 1.5moles of Hydrogen chloride gas (HCl)

Answer – 

1.5moles of HCl

1mole of HCl 6.02 x 1023

1.5 moles of HCl → x 

x = 6.02 x 1023 x 1.5moles of HCl

= 9.03 x 1023

 

(b) 3 moles of sodium trioxonitrate (V) (NaNO3)

Answer – 

3moles of NaNO3

1mole of NaNO3 → 6.02 x 103

3moles of NaNO3 →x

x = 6.02 x 1023x3

= 1.81 x 1024

 

(c) 0.2 moles of Lead (II) Chloride (PbCl2)

Answer – 

0.2moles of PbCl2

1mole of PbCl2 → 6.02×103

0.2moles of PbCl2 → x

x = 0.2 x 6.02 x 1023 x 3

= 1.20 x 1023

Question 1

(a) Define acid in terms of the following (i) Arrhenius (ii) Bronsted-Lowry (iii) Lewis

Answer – 

i. Arrhenius defined an acid as a substance that dissociates in water to produce hydrogen ion (H+) or proton.

ii. Bronsted-Lowry defined an acid as a proton donor.

iii. Lewis defined an acid as an electron-pair acceptor

 

(b) Give five examples of Organic acid and its sources

Answer – 

 

Organic Acid

Source

1.

Ethanoic acid

Vinegar

2.

Citric acid

Lime, Lemon

3.

Fatty acid

Fats and oils

4.

Amino acid

Protein

5.

Lactic acid

Milk

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