1. State that one mole = 6.02x10 23 2. Convert moles number of particles 3. Calculate the molar mass of a compound 4. Convert moles grams 5. Convert mass number of particles 6. Calculate the percentage composition of the elements of a compound when given the compound s formula. 7. Work out the empirical formula of a compound from mass data. 8. Work out the empirical formula of a compound from percentage composition data. 9. Work out the molecular formula of a compound when given molar mass and the empirical formula. 10. Work out the empirical formula and then the molecular formula of a compound when given mass/percentage composition data and molar mass. 11. Use percentage composition as a conversion factor Note: a strong grasp of scientific notation, significant figures and dimensional analysis is also required. 1. State that one mole = 6.02x10 23 One mole of a substance contains Avogadro s number of particles of that substance. State Avogadro s number. How many atoms in a mole of atoms? 2. Convert moles number of particles How many atoms in 4.2 mol of iron? How many moles in 1.2x10 24 molecules of carbon dioxide? How many atoms in 2.8 mol of neon? How many moles in 3.1x10 22 molecules of water? 3. Calculate the molar mass of a compound Calculate the molar mass of ammonium sulphide. Calculate the molar mass of magnesium sulphate (MgSO4).
4. Convert moles grams How many moles in 230.g of silver nitrate? What is the mass of 0.25 mol of sodium chloride? How many moles in 2.0g of carbon dioxide? What is the mass of 5.66 mol of calcium carbonate? 5. Convert mass number of particles How many molecules in 23g of boron trichloride? What is the mass of 7.3x10 25 fluorine molecules (F2)? How many molecules in 2.0g of carbon monoxide? What is the mass of 6.8x10 22 formula units * of potassium chloride? 6. Calculate the percentage composition of the elements of a compound when given the compound s formula. What is the percentage composition of Cr2O3? (1dp) What is the percentage composition of CaCl2? (1dp) * Formula units are the representative particles of ionic compounds.
7. Work out the empirical formula of a compound from mass data. Work out the empirical formula of a molecule containing 3.12g lithium, 2.72g carbon, and 10.83g oxygen. Work out the empirical formula of a compound that contains 2.27g of carbon, 3.6g of fluorine and 20.1g chlorine. 8. Work out the empirical formula of a compound from percentage composition data. Work out the empirical formula of a compound that is 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Work out the empirical formula of a compound that is 72.2% magnesium and 27.8% nitrogen by mass. 9. Work out the molecular formula of a compound when given molar mass and the empirical formula. Work out the molecular formula of ethylene glycol (it s found in antifreeze). The molar mass is 62g/mol and the empirical formula is CH3O. Work out the molecular formula of a compound with empirical formula P2O5. The molar mass is
283.9g/mol. 10. Work out the empirical formula and then the molecular formula of a compound when given mass/percentage composition data and molar mass. Methyl butanoate smells like apples. Its percentage composition is 58.8% carbon, 9.8% hydrogen and 31.4% oxygen. Its molar mass is 102 g/mol. Work out its empirical and molecular formulae. Nicotine is 74.1% carbon, 8.6% hydrogen, 17.3% nitrogen by mass. Its molar mass is 160 g/mol. Work out its empirical and molecular formulae. 11. Use percentage composition as a conversion factor Work out the mass of aluminium in 200.0 g of aluminium cyanide, Al(CN)3 Work out the mass of hydrogen in 151g of sodium hydride, NaH
Extension: 1) In the USA, the 23 rd of October is known as Mole Day. Can you think of a reason why? 2) A compound contains hydrogen, carbon and oxygen atoms in the ratio 6:2:1. What is the empirical formula of a compound? 3) Fertilisers often contain NH4NO3. a. State the name of the compound. b. Calculate the molar mass of the compound. c. Calculate the percentage composition of nitrogen in the compound. d. Calculate the number of oxygen atoms in 31g of NH4NO3. 4) Epinephrine is a hormone secreted into the bloodstream at times of danger and stress. It is 59.0% carbon, 7.1% hydrogen, 26.2% oxygen and 7.7% nitrogen by mass. Its molar mass is about 183 g/mol. Work out its molecular formula. (You will need to round a fair bit) 5) Calcium chloride is used to absorb household humidity. Water molecules become attached to each calcium chloride formula unit, forming a complex called a hydrate. a. State the formula of calcium chloride. b. Mary has found out that the calcium chloride hydrate contains 0.018 mol of water for every 0.0091 mol of calcium chloride. How many water molecules are attached to each calcium chloride formula unit? c. Explain why the term formula unit has been used, rather than molecule.
------------------------------------------------------------------------------------------------------------------------------------- Answers: (remember your answers might be off by a hundredth or so, depending on which periodic table you ve used) 1) 6.02x10 23 ; 6.02x10 23. 2) 2.5x10 24 atoms; 2.0mol; 1.7x10 24 atoms; 0.051mol. 3) 68.16g/mol; 120.37g/mol. 4) 1.35mol; 15g; 0.045mol; 567g. 5) 1.2x10 23 ; 4 600g; 4.3x10 22 ; 8.4g. 6) 68.4% Cr and 31.6% O; 36.1% Ca and 63.9% Cl. 7) Li2CO3; CFCl3. 8) CH2O; Mg3N2. 9) C2H6O2; P4O10. 10) Empirical: C5H10O2, Molecular: C5H10O2; Empirical: C5H7N, Molecular: C10H14N2. 11) 51.37g; 6.35g. Extension: 1) the date is 10/23. 2) H6C2O. 3)a) ammonium nitrate; b) 80.06g/mol; c) 35.00% d)7.0x10 23 ; 4) C9H13O3N; 5)a) CaCl2; b) about 2; c) calcium chloride is an ionic compound and ionic compounds are not made up of molecules because they are giant structures.