chemical equations Flashcards
what is a relative formula mass?
the relative atomic mass of all the atoms in a molecular formula added together. molecular mass
what is the formula for the % mass of an element in a compound.
% mass = (relative atomic mass of element x number of atoms of the element) ÷ relative formula mass of compound x 100
what is a mole?
the name for an amount of a substance.
what is the avogadro constant?
how many atoms are in a mole.
6.02 x 10^23.
what is the formula for the number of moles?
moles = mass g ÷ molecular mass Mr
what is conservation of mass?
in a chemical reaction no atoms are destroyed or created.
how do you know if a gas is formed in a chemical reaction?
the mass can change.
what does it mean if the mass increases in a chemical reaction?
one of the reactants is a gas. the gas which didn’t contribute to the original mass now contributes
what does it mean if the mass decreases in a chemical reaction?
one of the products is a gas. the liquid or solid which contributed to the original mass is now gas
what does the number in front of chemical formulas tell you?
the amount of moles of the substance.
what is the limiting reactant?
the reactant that gets completely used up in a reaction before the rest.
how do you calculate the amount of a product using the limiting reactant?
- write the balanced equation for the reaction.
- work out how many moles of the substances with given masses you have.
- find which is the limiting reactant. (by comparing the the equation)
- find how many moles of the product you will get by dividing the moles of the limiting reactant by the ratio of moles between it and the product in the equation.
- moles x mr = mass.
what is a decimetre?
1/10th of a metre.
how many decimetres does 1 mole of gas occupy?
24dm³.
what is the formula for volume of gas?
volume of gas dm³ = (mass of gas g ÷ molecular mass of gas) x 100
what is concentration?
the amount of substance in a volume.
what is the formula for concentration using mass of solute?
concentration g/dm³ = mass of solute g ÷ volume of solvent dm³
what is the formula for concentration using moles?
concentration mol/dm³ = moles in solute mol ÷ volume of solvent dm³
what is the formula for number of moles using volume?
moles = concentration x volume
what is a titration?
an experiment for finding the volume of 2 solutions needed to react completely.
what is atom economy?
the % of reactants forming useful products.
what is the formula for atom economy?
atom economy = molecular mass of desired product ÷ molecular mass of all reactants x 100
what are the problems with a low atom economy?
lots of waste.
uses lots of resources quickly.
aren’t profitable.
what is the yield?
the amount of product you get from a reaction.
