Unit 1 : Topic 1 Flashcards
Formulae, Equations and Amount of Substance
What is the unit used for the amount of substance?
The unit used is the mole (mol).
How is the number of particles in a sample calculated?
The number of particles can be calculated using the formula: Number of particles = Moles × Avogadro constant.
What is the empirical formula of Fe₂O₄?
For the chemical formula Fe₂O₄, the empirical formula is FeO₂.
What is the molecular formula if the empirical formula is C₄H₃O₂ and the relative molecular mass is 166?
The molecular formula is determined as C₈H₆O₄ by comparing the molecular and empirical masses.
What is relative formula mass?
Relative formula mass is the sum of the relative atomic masses of all atoms in a formula unit, often used for ionic structures.
What is 2 mg/cm³ equivalent to in ppm?
Convert 2 mg/cm³ to μg/cm³, resulting in 2000 ppm.
What is concentration?
Concentration is the amount of solute per cubic decimeter of solution.
What is an ion?
An ion is an atom or a group of atoms that carries an electric charge due to the loss or gain of electrons.
How is concentration in mol/dm³ calculated?
Concentration in mol/dm³ is Moles ÷ Volume (dm³).
What is an ionic equation?
An ionic equation shows only the reacting ions in a solution and excludes spectator ions.
For example, Ag(aq) + Cl⁻(aq) → AgCl(s).
How many moles of iron are in a sample with 4.816 × 10²⁴ atoms?
Divide the number of atoms by the Avogadro constant, resulting in 8 moles of iron.
What does a chemical equation tell us about the number of moles of reactants and products?
The stoichiometric ratio indicates the relationship between reactants and products.
For example, C₃H₈ + 5O₂ → 3CO₂ + 4H₂O, one mole of propane produces four moles of water.
What is the empirical formula?
The empirical formula is the simplest ratio of the number of atoms of each element in a compound.
What is 1 ppm equivalent to?
For mass/volume concentrations, 1 ppm = 1 g/m³ = 1 mg/L = 1 μg/cm³. For mass/mass concentrations, 1 ppm = 1 mg/kg = 1 μg/g.
What is molar mass?
Molar mass refers to the mass of one mole of a substance, expressed in grams per mole.
What is the Avogadro constant?
The Avogadro constant is the number of particles in one mole, equal to 6.02 × 10²³.
What is parts per million (ppm)?
Parts per million measures the ratio of one substance to another.
How is the volume of a gas at RTP calculated?
The volume is Moles × 24.
What is a mole?
A mole refers to the amount of a substance containing the same number of particles as there are atoms in 12 grams of carbon-12.
What are the general products of a reaction between an acid and a metal?
The reaction produces a salt and hydrogen gas: Acid+Metal→Salt+ Hydrogen
What is the percentage yield of ammonia if 40.5 g is produced from 20.0 mol of hydrogen with excess nitrogen?
For this reaction N2+3H2→2NH3
- The theoretical yield of ammonia is 227 g.
- The percentage yield is (40.5÷227)×100=17.9%
What is the molecular formula?
The molecular formula shows the exact number of atoms of each element present in a compound.
Why might the actual yield be less than the theoretical yield?
- The reaction may be incomplete.
- Side reactions may occur.
- Practical losses during transfer of materials may happen.
What is the ideal gas law?
The ideal gas law is PV = nRT, where P is pressure (Pa), V is volume (m³), n is moles, R is the gas constant (8.31 J/K·mol), and T is temperature (K).
