Quantitative chemistry Flashcards
The law of conservation states that ….
no atoms are lost or made during a chemical reaction so the mass of the product equals the mass of the reactants.
Give two examples of a reaction where a change in mass may appear to take place.
Metal reacting with oxygen or an acid. Thermal decomposition.
Why does the water, produced during the reaction, have a
lower mass than the original hydrogen peroxide?
Because the oxygen gas produced during the reaction escaped into the atmosphere.
What is the relative formula mass of a compound?
Sum of the relative atomic masses of the atoms in the numbers shown in the formula.
What can be said about the sum of the relative formula masses of the reactants and products of a reaction?
In a balanced chemical equation – the sum of the relative
formula masses of the reactants in the quantities shown = sum of the relative formula masses of the products in the quantities shown.
What is meant by the term ‘mole’?
A measure of the chemical amount of a substance.
What is meant by the term ‘limiting reactant’?
A reactant in a reaction which is completely used up when the other reactant is in excess.
number of mole =
mass (g) / Ar or mass (g) /Mr
Concentration (g/dm3 ) =
amount of solute (g) / Volume of solution (dm3)
What does dm^3 mean?
1000cm^3
Give the equation for calculating concentration from the mass of substance and volume of solution.
Concentration = mass ÷ volume
