Quiz 12 of 20

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

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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

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)

n = $$\frac{2.7}{27}$$

n = 0.1g

(c) 7.15g of Potassium Chloride (KCl)

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)

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

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)

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)

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)

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)

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

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

 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

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)

n = $$\frac{2.7}{27}$$

n = 0.1g

(c) 7.15g of Potassium Chloride (KCl)

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)

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

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)

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)

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)

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)

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

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