C3-Quantitative Chemistry Flashcards
What is the relative atomic mass?
The relative atomic mass of an element is the average mass of the isotopes of that element weighted to take into account the abundance of each isotope
What is the relative formula mass of an element?
The relative formula mass is the sum of the relative atomic masses of the atoms in the numbers shown in the formula
What is the relative formula mass of CH4
ram of carbon=12 ram of hydrogen=1
so it is (12x1)+(4x1)=RFM
RFM=16
What is 1 mole of an atom ?
6.02x10^23
What is 1 mole of an atom ?
6.02x10^23 (avogadro’s constant)
How do you work out the number of moles in a substance?
Number of moles=mass(g)/relative formula mass
What is the law of Conservation of mass?
the law of conservation of mass state that no atoms are lost during or made during a chemical reaction so the mass of the products equals the mass of the reactants.
What is a limiting reactant in a chemical reaction?
in a chemical reaction involving two reactants,it is common to use an excess of one of the reactants to ensure that all of the other reactant is used.the reactant that is completely used up is called the limiting reactant
What are the 2 formulae that link concentration,mass/mole and volume together?
concentration=mass/volume
concentration=mole/volume
when mass seems to change how is gas involved?(increases)
if mass increases it is because one of the reactants is a gas that’s found in air and all the products are solids,liquids or aqueous.
when there is a decrease in mass how is gas involved?
if the mass decreases it is because one of the products is a gas and all the reactants are solids,liquids or aqueous
How can you balance equations using reaction masses?
1- divide the mass of each substance by its RFM to find the number of moles
2-divide the number of moles of each substance by the smallest number of moles in the reaction
3-if any of the numbers aren’t whole times all the numbers by the same number so they can become whole
4-write the balanced symbol equation for the reaction by putting these numbers in front of the chemical formulae
Why do reactions stop?
reactions stop when 1 reactant is used up
What is a concentration of a solution?
the more solute there is in a given volume,the more concentrated the solution
What is percentage by mass?
A value representing the concentration of an element in a compound
or a component in a mixture. It is calculated by the mass of a component divided by the total
mass of the mixture, multiplied by 100.
