Stoichiometry

Question 1

How to find empirical formula?

Answer 1

1. Write down mass of each element, If % is given, let mass of compound be 100%
2. Write the molar mass of each element
3. Calculate the no. of moles (mass/molar mass)
4. Divide by smallest number (leave in 4sf)
5. Obtain a whole number ratio

Question 2

What are the 2 ways to calculate concentration?

Answer 2

1. Moles of solute per dm3,
   mole of solute(mol) / vol of solution in dm3 =mol/dm3
2. Mass of solute per dm3
   mass of solute (g) / vol of solution in dm3 =g/dm3

Question 3

How to calculate percentage yield?

Answer 3

Experimental mass / Maximum possible mass of produced x 100%

Question 4

How to calculate percentage purity?

Answer 4

Mass of pure percentage present / Mass of sample x 100%

Question 5

What are the general steps to solve any qns?

Answer 5

1. Construct balanced chemical equation
2. Find no. of mole of known substance
3. 5 Finding limiting reactant if BOTH quantity of reactants are given
4. Compare the mole ratio
5. Find the no. of mole of unknown substance
6. Convert mole into mass/conc/vol required