3: Equations, Calculations And Electrolysis Flashcards
(18 cards)
What is a mole?
6.02 × 10²³ particles of a substance.
How do you calculate moles?
Moles = Mass (g) ÷ Mᵣ.
What equation calculates mass of a product?
Moles = Mass ÷ Mᵣ.
How do you calculate percentage yield?
% Yield = (Actual ÷ Theoretical) × 100.
What is the empirical formula?
The simplest whole number ratio of atoms.
How is molecular formula calculated?
the question gives you the empirical formula and the mollecular mass:
1) find the mass of the emperical formula
2) divide the mollecular mass by the empircal mass to find how much bigger the mollecular mass is compared to the emperical mass
3) multiply each subscript of the emperical formula by the multiple from step 2.
What method calculates empirical formula in combustion?
Heat metal in oxygen and measure masses of oxide formed.
What is water of crystallisation?
Water molecules in a salt’s lattice.
How do you calculate water of crystallisation?
Moles of water ÷ Moles of anhydrous salt.
What is the concentration formula?
Concentration = Moles ÷ Volume (dm³).
How do you convert between mol/dm³ and g/dm³?
Mass (g) = Moles × Mᵣ.
What volume does 1 mole of gas occupy at RTP?
24 dm³.
How do you calculate gas volume?
Volume = Moles × 24.
What happens at the cathode in electrolysis?
Positive ions gain electrons (reduction).
What happens at the anode in electrolysis?
Negative ions lose electrons (oxidation).
What gases form at electrodes in aqueous solutions?
H₂ at cathode, O₂ or halogen at anode.
What’s a half-equation for H₂ at the cathode?
2H⁺ + 2e⁻ → H₂.
