Quantitative Chemistry Flashcards
How do you calculate the relative formula mass (Mr) of a substance?
Find the relative atomic masses of all the elements in the substance and add them together.
State the value of avogadro’s constant
6.02 x 10²³
What is the formula that relates the number of moles of a substance to its mass and Mr?
Number of moles = mass in g (of element or compound) / Mr (of element or compound)
What does conservation of mass mean?
No atoms are lost or gained in the reaction.
Suggest why the mass of a reaction vessel might decrease during a reaction.
One of the products is a gas (and therefore cannot be weighed beforehand)
How can you determine the number of moles of each substance that would react together from the balanced reaction equation?
The large number to the left of a symbol is how many moles there are.
Explain what is meant by ‘limiting reactant’
The reactant that runs out first and therefore stops the reaction from happening.
What is concentration?
The amount of substance (dissolved) in a volume of solution.
Give the equation for working out the concentration of a solution in g/dm³
concentration = mass of solute / volume of solvent
