# ICSE Class 10th Chemistry 4 – Mole Concept and Stoichiometry MCQs

#### ____ moles of magnesium phosphate will contain 0.25 moles of oxygen.

Correct! Wrong!

8 moles of oxygen are present in =1 mole of magnesium phosphate (Mg3 (PO4)2) 0.25 moles of oxygen = 1 × 0.25 ÷ 8 = 3.125 × 10-2 moles

#### The molarity of commercially available concentrated sulphuric acid of 95% by mass would be ____. (Given the density of sulphuric acid is 1.84 gm cm-3)

Correct! Wrong!

Density = 1.84 gm/cc; 1 cc contains 1.84 gm of sulphuric acid Therefore, 1 litre will contain 1.84 × 1000 = 1840 gms. Percentage purity of sulphuric acid = 95 % Therefore, mass of pure sulphuric acid present = 95 × 1840 ÷ 100 = 1748 gms. Hence, molarity = mass/molar mass = 1748 ÷ 98 = 17.8 M

#### Phosphorus is

Correct! Wrong!

Tetratomic molecule composed of 4 similar atoms.

#### A person adds 2 gms of sugar (C12H22O11)in order to sweeten his coffee. The number of carbon atoms added to his coffee would be ____. (Molar mass of sugar = 342)

Correct! Wrong!

1 mole of any substance contains 6.023 × 1023 atoms. 1 mole of any substance would weigh molar mass of that substance. Therefore, 342 gms of sugar = 1 mole of sugar 342 gms of sugar = 6.023 × 1023 molecules of sugar or 12 × 6.023 × 1023 atoms of carbon When 2 gms of sugar are added, the carbon atoms added = 12 × 6.023 × 1023 atoms of carbon × 2 ÷ 342 = 4.226 × 1022 atoms of carbon.

#### What is the total mass of products in the following equation: 2KClO3→2KCl+3O22KClO3→2KCl+3O2(catalyst)

Correct! Wrong!

Total mass of product = 2(39 + 35.5) + 3(32) = 149 + 96 = 245g

#### Of the options given below, which pair has same percentage of carbon?

Correct! Wrong!

Calculate the percentage of carbon in each compound. % age = mass of carbon present × 100 ÷ molar mass of the compound C6H12O6 = 6 × 12 × 100 ÷ 180 = 40% C12H22O11 = 12 × 12 × 100 ÷ 342 = 42% CH3COOH = 12 × 2 × 100 ÷ 60 = 40 % C2H5OH = 12 × 2 × 100 ÷ 46 = 52%

#### 160 c.c acetylene reacts with 500c.c oxygen. Calculate the total volume of resulting gaseous mixture.

Correct! Wrong!

The balanced equation of combustion of acetylene is 2C2H2 (g) +5O2 (g) =4CO2 (g) +2H2O (l) 2 VOLS = 160 c.c 1 vol = 80 c.c 5 vol of oxygen = 400c.c so, (500-400) c.c = 100 c.c is unreacted. 4 vols = 320 c.c Water is in liquid state. Total volume = (100+320) c.c = 420 c.c

#### What is the empirical formula of Butane?

Correct! Wrong!

Molecular Formula is = C4H10 Ratio of C, H is = 4:10 Simple ratio = 2:5 Empirical Formula = C2H5

#### What is the ratio of carbon dioxide prepared from CO and O2?

Correct! Wrong!

The reaction is 2CO+O2=2CO And the ratio is = 2:1:2

#### Octatomic molecule is

Correct! Wrong!

Octatomic molecule composed of 8 similar atoms.

#### Of the options given, ____ is the heaviest.

Correct! Wrong!

Option A - 1 mole of Oxygen = 32 gms Option B - 10 moles of hydrogen = 2 × 10 = 20 gms Option C - 44 gms of carbon dioxide Option D - 1 molecule of sulphur dioxide = 64/ 6.023 × 1023 = 10.6 × 10-23 gms Hence, Option C is the heaviest.

#### What volume of oxygen would be required to burn completely 350 ml of acetylene?

Correct! Wrong!

The balanced equation of combustion of acetylene is 2C2H2+5O2=4CO2+2H2O 2Vols = 350 ml or, 5 vols = 875 ml

#### Molecular mass of sugar is (in a. m. u) _

Correct! Wrong!

Formula is C12H22O11 Molecular mass= (12×12) + (1×22) + (11×16) = 144 + 22 + 176 = 342 a. m. u

#### 6 litre chlorine is reacted with 10 litre sodium. The excess amount of sodium is _

Correct! Wrong!

The balanced equation is 2Na+Cl2=2NaCl Ratio is = 2:1:2. 6 litre chlorine reacts with 12 litre sodium. So, there is no excess of sodium.

#### The mass of carbon present in 0.5 mole of K4[Fe(CN)6] is ____.

Correct! Wrong!

1 mole of K4[Fe (CN)6] contains 6 gm. atom of carbon atoms. 0.5 mole of K4[Fe (CN)6] will contain 6 x 0.5 = 3 gm atom of carbon atoms. Hence, mass of carbon present in 0.5 mole of K4[Fe (CN)6] = 3 x 12 = 36 gms.

#### In Boyle’s Law the fixed parameter is _

Correct! Wrong!

Boyle’s law state that at constant temperature pressure of a given mass of a dry gas is inversely proportional to its volume.

#### Mass and temperature both are fixed in _

Correct! Wrong!

Boyle’s law state that at constant temperature pressure of a given mass of a dry gas is inversely proportional to its volume.

#### What volume of carbon di oxide would be required to burn completely 500 ml of acetylene?

Correct! Wrong!

The balanced equation of combustion of acetylene is 2C2H2+5O2=4CO2+2H2O 2Vols = 500 ml or, 4 vols = 1000ml

#### Ozone is _

Correct! Wrong!

Formula of ozone is O3. So, the atomicity is 3 i.e. it is a triatomic molecule.

#### Given are four mathematical relationships. The incorrect expression is ____.

Correct! Wrong!

The incorrect expression is Number of moles = Atomic mass ÷ Mass of the element in grams. The correct expression for Number of moles = mass in gms ÷ molar mass

#### 150c.c of ethylene burnt in sufficient air. The amount of required oxygen is

Correct! Wrong!

The balanced equation of combustion of acetylene is C2H4+3O2 = 2H2O 1 vol ethylene require 3 volumes of oxygen. (3×150) = 450c.c of oxygen.

#### Atomicity is _

Correct! Wrong!

Number of atoms in a molecule

#### In Avogadro Law, the fixed parameter is

Correct! Wrong!

Avogadro’s Law states that equal volumes of all gases under similar conditions of temperature and pressure contain the same number of molecules.

#### An analysis of an inorganic salt gave the following percentage composition: Na = 14.28 %; S = 9.92 %; H = 6.20 % Assuming all the hydrogen combines with oxygen to form water, and the molecular mass of the crystalline salt is 322, the correct molecular formula would be ____ .

Correct! Wrong!

Hence, the empirical formula is Na2SH20O14 The molecular formula = n × empirical formula or n = molecular weight/ empirical formula weight Molecular weight = 322 Empirical formula weight = 2 × 23 + 1 × 32 + 20 × 1 + 14 × 16 = 322 n = 322 / 322 = 1 So, the molecular formula is same as empirical formula.

#### A student analysed a given inorganic salt to determine the water of crystallization. The observations recorded are: Fe2+= 14.32 %; SO42- = 49 %; NH4+= 9.2 % and H2O = 27.57 % The reported number of moles of water in the salt would be ____ .

Correct! Wrong!

Therefore, the number of moles of water = 6 moles in the salt (It is the water of crystallization)

ICSE Class 10th Chemistry 4 - Mole Concept and Stoichiometry MCQs
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