Chemistry: Conversion Factors and Masses

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Questions and Answers

What is the symbol used to represent Avogadro's number?

What is the formula for calculating the percentage purity of a compound?

(%purity = (Actual mass of compound) / (Total mass of sample) * 100

Which of the following is NOT a conversion factor listed in the text?

1 calorie = 4.184 J

1 litre = 10⁻³ m³

1 Å = 10⁻¹⁰m

1 g = 1000 mg (correct)

The mass of one atom or molecule in ______ is called the atomic mass or molecular mass.

a.m.u. Signup and view all the answers

The vapor density of a substance is the ratio of its density to the density of hydrogen at the same temperature and pressure.

True Signup and view all the answers

What is the formula for calculating the volume of a gas at STP (Standard Temperature and Pressure) when you know the number of moles?

Volume of gas = Number of moles * 22.4 L/mol Signup and view all the answers

What does 'STP' stand for in chemistry?

Standard Temperature and Pressure Signup and view all the answers

Which of these is a defining characteristic of a Limiting Reagent?

It is the reactant that is completely consumed in a reaction. Signup and view all the answers

Match each concentration term with its corresponding mathematical formula.

Percentage by mass = Mass of solute × 100 / Mass of solution Mass-volume percentage = Mass of solute × 100 / Volume of solution Parts per million = Mass of solute × 10⁶ / Mass of solution Mole fraction = Mole of a / (Mole of A + Mole of B + Mole of C + ...) Molarity = Mole of solute / Volume of solution (in L) Molality = Mole of solute / Mass of solvent (Kg) Signup and view all the answers

The concept of mixing solutions is based on the law of conservation of mass.

False Signup and view all the answers

What is the formula for calculating the final molarity of two solutions with the same solute when they are mixed?

Final Molarity = (M₁V₁ + M₂V₂) / (V₁ + V₂) Signup and view all the answers

What does the mass number of an atom represent?

The total number of protons and neutrons in the nucleus Signup and view all the answers

Which type of bonding involves the transfer of electrons between atoms?

Ionic bonding Signup and view all the answers

In a solution, the substance that is dissolved is referred to as the:

Solute Signup and view all the answers

What do balanced chemical equations represent?

The quantitative relationship between reactants and products Signup and view all the answers

Why is carbon essential to organic chemistry?

It has a unique ability to form strong covalent bonds with other atoms Signup and view all the answers

What defines an acid according to the Arrhenius definition?

A substance that donates protons Signup and view all the answers

Which of the following statements about compounds is true?

Compounds are formed from two or more different types of atoms. Signup and view all the answers

Which statement best describes the concept of Gibbs free energy?

It measures the maximum reversible work at constant temperature and pressure. Signup and view all the answers

How does entropy change in an isolated system according to the second law of thermodynamics?

Entropy can only increase over time. Signup and view all the answers

What is a characteristic of gaseous matter?

It expands to fill its container. Signup and view all the answers

In the context of reaction rates, which factor can influence the rate of a chemical reaction?

Concentration of the reactants Signup and view all the answers

What does the equilibrium constant (K) represent in a chemical reaction?

The ratio of reactants to products at equilibrium. Signup and view all the answers

Which of the following is a characteristic of a solid state of matter?

It has a definite shape and volume. Signup and view all the answers

Study Notes

Useful Conversion Factors

1 Å = 10^-10 m
1 nm = 10^-9 m
1 pm = 10^-12 m
1 L = 10^-3 m³ = 1 dm³
1 atm = 760 mmHg or torr = 101325 Pa or Nm^-2
1 bar = 10⁵ Nm^-2 = 10⁵ Pa
1 calorie = 4.184 J
1 eV = 1.6022 × 10^-19 J
1 J = 10⁷ ergs

Atomic Mass or Molecular Mass

Mass of one atom or molecule in amu
C → 12 amu
NH₃ → 17 amu

Actual Mass

Mass of one atom or molecule in grams
C → 12 × 1.6 × 10^-24 g
CH₄ → 16 × 1.6 × 10^-24 g

Relative Atomic Mass or Relative Molecular Mass

Mass of one atom or molecule relative to 1/12th of ¹²C atom
C → 12
CH₄ → 16
Unitless

Gram Atomic Mass or Gram Molecular Mass

Mass of one mole of atom or molecule
C → 12 g
CO₂ → 44 g
Also called molar mass

Definition of Mole

One mole is a collection of entities equal to the number of atoms in exactly 12 g of ¹²C isotope
Avogadro's number (N_A) = 6.022 × 10²³

For Elements

1 g-atom = 1 mole of atoms = N_A atoms
Gram atomic mass (GAM) = mass of N_A atoms in g

For Molecules

1 g-molecule = 1 mole of molecule = N_A molecules
Gram molecular mass (GMM) = mass of N_A molecules in g

1 Mole of Substance

Contains 6.022 × 10²³ particles
Weighs as much as molecular/atomic/ionic mass in grams
1 mole of gas occupies 22.4 L at STP or 22.7 L at STP

For lonic Compounds

1 g formula unit = 1 mole of formula unit = N_A formula unit
Gram formula mass (GFM) = mass of N_A formula unit in g

Vapour Density

Ratio of vapour density to the density of hydrogen at similar pressure and temperature

Stoichiometry Based Concept

aA + bB → cC + dD
a, b, c, d represent mole ratios (or volume ratios for gases) in a chemical reaction
Do not represent mass ratios
Moles of reactants/products in a balanced equation are in ratios

Percentage Purity

% purity = (Actual mass of compound / Total mass of sample) × 100
Impurities are treated as inert materials

Empirical and Molecular Formula

Empirical formula: Simplest whole number ratio of atoms in a compound
Molecular formula: Actual number of atoms in a molecule
Molecular formula = Empirical formula × n

Concept of Limiting Reagent

If data of more than one reactant is given, first convert to moles
Then divide moles of reactants by their stoichiometric coefficients

Concentration Terms

Several concentration units are presented (percentage by mass, volume etc) -Expressed as mathematical formula and concept

Mixing of Solutions

Based on the law of conservation of moles
For solutions containing the same solute
- Final molarity = (Total moles/Total volume)
Dilution effect
- M₁V₁ + M₂V₂ = M₃(V₁ + V₂)

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Description

Test your knowledge on useful conversion factors and the concepts of atomic and molecular mass in chemistry. This quiz covers topics such as actual mass, relative atomic mass, and gram molecular mass, along with definitions of a mole. Perfect for students wanting to solidify their understanding of these key concepts.