Quantative Chemistry (paper 1) Flashcards
(18 cards)
What is the law of conservation of mass?
No atoms are lost or made during a chemical reaction, so the mass of the products equals the mass of the reactants.
What does a balanced chemical equation indicate?
It indicates that there are exactly the same number of atoms of each element on both sides of the equation.
What is the relative formula mass (Mr)?
It is the sum of the relative atomic masses of all the atoms in a formula.
What is the conservation of mass?
No atoms are lost or made during a chemical reaction, so the mass of the products equals the mass of the reactants.
Why might it look like mass increases in a reaction?
A gas from the air is added into the product (e.g. oxygen in metal burning).
Why might it look like mass decreases in a reaction?
A gas is released into the air and is no longer part of the reaction mixture.
How do you calculate the relative formula mass (Mr)?
Add the Ar (relative atomic mass) values of each atom in the formula.
How do you calculate the percentage mass of an element in a compound?
Percentage mass = (Ar of element × number of atoms / Mr of compound) × 100
What is the equation for number of moles?
Moles = mass (g) / Mr
What is a balanced symbol equation?
An equation where the number of each type of atom is the same on both sides.
Why is balancing equations important in quantitative chemistry?
To make sure calculations based on ratios of reactants and products are accurate.
What is a limiting reactant?
The reactant that is used up first and limits how much product is made.
What happens when the limiting reactant is used up?
The reaction stops because there’s no more of that substance to react.
What is concentration?
It’s the amount of substance (in moles or grams) in a given volume of solution.
What is the equation for concentration in g/dm³?
Concentration (g/dm³) = mass (g) / volume (dm³)
What is the equation for concentration in mol/dm³?
Concentration (mol/dm³) = moles / volume (dm³)
What kind of reaction is used to make a salt from an acid and a base?
Neutralisation reaction.
What steps are followed in the required practical to make a salt?
- Add excess base to acid. 2. Filter off the excess. 3. Heat to evaporate water and get crystals.
