The Mole Concept, Chemical Formula and Equation

Activity 3.14:Solving numerical problems involving empirical formulae and molecular formulae[Relative atomic mass: H = 1, C = 12, N = 14, O = 16, Ca = 40, Zn = 65]1. Ethanoic acid has a molar mass of 60 g mol–1. If its empirical formula is CH2O, determine the molecular formula of ethanoic acid.2. Hydrocarbons consist … Read more

Activity 3.13:Aim: To determine the empirical formula of copper(II) oxide.Materials: Water, copper(II) oxide powder, zinc granules, 1.0 mol dm–3 hydrochloric acid, wooden splinter and cotton budsApparatus: Boiling tube, rubber stoppers, rubber tube, 12 cm glass tube, 10 cm glass tube, spirit lamp, retort stand with clamp, wooden block, electronic balance and spatulaProcedure: 1. Weigh the … Read more

Activity 3.12:Aim: To determine the empirical formula of magnesium oxide.Materials: 10 cm magnesium ribbon and sand paperApparatus: Crucible with lid, tongs, Bunsen burner, tripod stand, pipeclay triangle and electronic balanceProcedure:1. Weigh and record the mass of a crucible together with its lid.2. Rub 10 cm magnesium ribbon with a sand paper until shiny. Coil the … Read more

Activity 3.11:Determining the empirical formulae[Relative atomic mass: H = 1, C = 12, O = 16, Cl = 35.5, K = 39, Br = 80, Sn = 119, I = 127]1. A sample of potassium bromide contains 6.24 g of potassium and 12.8 g of bromine. What is the empirical formula of potassium bromide?2. A … Read more

Test Yourself 3.2:[Relative atomic mass: H = 1, C = 12, N = 14, O = 16, Na = 23, Cl = 35.5, K = 39, Fe = 56, Pb = 207; Avogadro constant, NA: 6.02 × 1023 mol–1; Molar volume: 22.4 dm3 mol–1 at STP or 24 dm3 mol–1 at room conditions]1. Calculate the … Read more

Activity 3.9:Solving problems involving the number of particles, number of moles, mass of substances and volume of gases at STP or room conditions1. Carry out this activity in groups.2. Read and answer the following questions. [Relative atomic mass: H = 1, He = 4, C = 12, N = 14, O = 16, Al = … Read more

Activity 3.7:Calculating the number of moles and volume of gases [Molar volume of gas = 22.4 dm3 mol–1 at STP or 24 dm3 mol–1 at room conditions]1. Calculate the volume of 0.6 mol of chlorine gas, Cl2 at STP and room conditions.2. Calculate the number of moles of each of the following gases:(a) 48 cm3 … Read more

Activity 3.6:Calculating the number of moles and mass [Relative atomic mass: H = l, C = 12, N = 14, O = 16, Mg = 24, S = 32, Fe = 56; Avogadro constant, NA : 6.02 × 1023 mol–1]1. Calculate the mass of each of the following substances: (a) 0.4 mol of iron fillings, … Read more

Activity 3.5:Calculating the number of moles and number of particles[Avogadro constant, NA : 6.02 × 1023 mol–1]1. Calculate the number of atoms found in (a) 0.1 mol of carbon, C (b) 3.5 mol of neon gas, Ne2. Calculate the number of molecules found in (a) 1.2 mol of hydrogen gas, H2(b) 0.8 mol of ammonia, … Read more

Test Yourself 3.1:1. Define relative atomic mass based on the carbon-12 scale.2. Refer to the Data Table of Elements on page 276 to get the relative atomic masses. (a) How many atoms of lithium are required to equalise the mass of one atom of krypton? (b) How many atoms of helium are required to equalise … Read more