What is the Relative formula mass (Mr) of CO (carbon monoxide)? Carbon=12, Oxygen=16.
28
192
What is the Relative atomic mass of a sodium atom?
11
23
What is the relative formula mass of sodium oxide (Na2O)? Ar sodium=23, Ar oxygen=16.
39
62
If you convert the relative atomic mass or the relative formula mass of an atom into grams, you get 1mole of the chemical.
What is the equation to find the % mass of an element in a compound?
% mass of an element in a compound = Ar x number of atoms (of that element) / Mr (of whole compound)
% mass of an element in a compound = Ar x number of atoms (of whole compound) / Mr (of that element)
Take NaOH. What is the % mass of oxygen?
40%
65%
What is the empirical formula of a compound?
The smallest ratio of atoms present in a compound
Something that enables you to rule the world!
This is how you calculate the empirical formula of a compound: 1. Write down the mass of each element 2. Divide the mass by the relative atomic mass (Ar) of the element 3. Divide the numbers by the smallest number to get the ratio of elements 4. Put the ratios in their simplest forms
A compound is made from 72g carbon and 12g of hydrogen. What is its empirical formula?
C2H
CH2
How do you calculate moles?
m= n x M (m=mass, n=moles, M=molar mass)
M=n x m (m=mass, n=moles, M=molar mass)
This is how you calculate % yield: 1. Write out the equation 2. Balance the equation 3. Work out Mr for every reactant and product in the equation 4. Work out how many moles of reactant there are in the mass given in the question 5. Work out the mass of product you should make for 100% yield 6. Calculate % yield using the formula
What is the equation for working out the % yield?
% yield = maximum amount of product produced / minimum amount of product possible x100
% yield = amount of product produced / maximum amount of product possible x100
In an experiment, 11.5g of sodium is reacted with an excess of chlorine. The mass of sodium chloride made is 23.4g. a) What is the maximum amount of product that could be made. b) What is the % yield.
80%
29.25%
