Mole Concept in Chemistry

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Questions and Answers

What is the molar mass of A (MA) and molar mass of B (MB) in kg mol-1?

MA = 25 × 10−3 and MB = 50 × 10−3

MA = 50 × 10−3 and MB = 25 × 10−3 (correct)

MA = 5 × 10−3 and MB = 10 × 10−3

MA = 10 × 10−3 and MB = 5 × 10−3

What is the percentage composition of carbon by mole in methane?

20%

75%

25% (correct)

80%

What is the mole fraction of NaOH in the solution and the molality (in mol kg-1) of the solution if 8 g of NaOH is dissolved in 18 g of H2O?

0.167, 22.20

0.167, 11.11 (correct)

0.2, 22.20

0.2, 11.11

What is the volume strength of 1 M H2O2?

11.35 Signup and view all the answers

What is the molecular weight of AB2?

125 g Signup and view all the answers

What is the molecular weight of A2B2?

300 g Signup and view all the answers

What is the ratio of the molecular weight of A to the molecular weight of B?

2:1 Signup and view all the answers

What is the percentage of oxygen in a human adult?

61.4% Signup and view all the answers

What is the total mass of 5 moles of AB2 and 10 moles of A2B2?

425 g Signup and view all the answers

If the polar head is approximated as a cube, what is its edge length?

2.0 pm Signup and view all the answers

What is the weight gained by a 75 kg person if all H atoms are replaced by 2H atoms?

37.5 kg Signup and view all the answers

Which of the following reaction mixtures has dihydrogen (H2) as a limiting reagent?

14 g of N2 + 4 g of H2 Signup and view all the answers

What is the molar mass of M2CO3 in g mol⁻¹?

1186 Signup and view all the answers

What is the amount of sugar (C12H22O11) required to prepare 2 L of its 0.1 M aqueous solution?

136.8 g Signup and view all the answers

What is the molecular mass of sugar (C12H22O11)?

342 Signup and view all the answers

What is the mole of CO2 produced when 1 g of a carbonate (M2CO3) is treated with excess HCl?

0.01186 Signup and view all the answers

What is the balanced equation for the combustion of hydrocarbon C4H8?

C4H8 + 6O2 → 4CO2 + 4H2O Signup and view all the answers

What is the mole ratio of CO2 to O2 in the combustion reaction of hydrocarbon C4H8?

1:1 Signup and view all the answers

What is the mass of water produced from the combustion of 445 g of C57H110O6?

445 g Signup and view all the answers

What is the molality of Na+ ions in a solution of sodium sulphate that contains 92 g of Na+ ions per kilogram of water?

132 Signup and view all the answers

What is the area covered by 10 mL of a 1 mM surfactant solution?

0.24 cm^2 Signup and view all the answers

What is the ratio of the number of moles of CO2 to the number of moles of O2 required for the complete combustion of a hydrocarbon?

4:5 Signup and view all the answers

Study Notes

Mole Concept

The mole concept is a fundamental concept in chemistry that deals with the amount of substance.
A mole is a unit that represents 6.022 x 10^23 particles (atoms, molecules, ions, or electrons).
The mole is used to express the amount of a substance, and it is a convenient way to express the amount of a substance in a reaction.

Percentage Composition

The percentage composition of carbon by mole in methane is 75%.
The percentage composition of an element in a compound is the ratio of the mass of the element to the mass of the compound, multiplied by 100.

Mole Fraction and Molality

The mole fraction of a solute in a solution is the ratio of the number of moles of the solute to the total number of moles of the solution.
The molality of a solution is the number of moles of the solute per kilogram of the solvent.
For example, 8 g of NaOH is dissolved in 18 g of H2O, the mole fraction of NaOH in the solution is 0.2, and the molality is 11.11 mol/kg.

Stoichiometry

The minimum amount of O2 consumed per gram of reactant depends on the reaction.
For example, for the reaction C3H8 + 5O2 → 3CO2 + 4H2O, the minimum amount of O2 consumed per gram of reactant is 5 moles of O2 per mole of C3H8.
For the reaction P4 + 5O2 → P4O10, the minimum amount of O2 consumed per gram of reactant is 5 moles of O2 per mole of P4.

Hydrocarbons

The formula of a hydrocarbon can be determined by its combustion reaction.
For example, if 10 mL of a hydrocarbon requires 55 mL of O2 for complete combustion and produces 40 mL of CO2, the formula of the hydrocarbon is C4H10.

Surfactants

A surfactant is a substance that reduces the surface tension of a liquid.
The edge length of a polar head of a surfactant can be calculated by approximating it as a cube.
For example, if 10 mL of a 1 mM surfactant solution forms a monolayer covering 0.24 cm^2 on a polar substrate, the edge length of the polar head is 0.1 nm.

Chemical Reactions

The limiting reagent in a reaction is the reactant that is consumed first.
For example, in the reaction N2 + 3H2 → 2NH3, dihydrogen (H2) is the limiting reagent if the reaction mixture contains 56 g of N2 and 10 g of H2.

Carbonate Reactions

A carbonate (M2CO3) reacts with excess HCl to produce CO2.
The molar mass of the carbonate can be calculated from the amount of CO2 produced.
For example, if 1 g of a carbonate produces 0.01186 moles of CO2, the molar mass of the carbonate is 118.6 g/mol.

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Description

Basic concepts in chemistry, including mole concept and percentage composition. Objective questions for practice.