Quiz 12 of 20

# SS1: Chemistry 2nd Term Theory Questions – Mole Concept

#### Responses error:

## 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 + 14x2 + 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 = 16x2 = 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 → 6.02x103

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

## 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 + 14x2 + 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 = 16x2 = 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 → 6.02x103

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