Reaction Coefficient

Reaction Coefficient The reaction coefficient is the ratio of the number of particles of the substance involved in the reaction. Because 1 mole of each substance contains the same number of particles, the ratio of the number of particles is equal to the ratio of the number of moles. So, the reaction coefficient is the ratio of the number of moles of substances involved in the reaction. For reactions: N2 (g) + 3 H2 (g) 2 NH3 (g) the reaction coefficient states that 1 molecule of N2 reacts with 3 molecules of H2 to form 2 molecules of NH3 or 1 mole of N2 reacts with 3 moles of H2 to produce 2 moles of NH3 (coefficient 1 is never written). With this understanding, the amount of substance needed or produced in a chemical reaction can be calculated using the equivalent reaction equation. If the number of moles of one of the reacting substances is known, then the number of moles of the other substance in the reaction can be determined by using the ratio of the reaction coefficients. Example 1. 1. Aluminum dissolves in a solution of sulfuric acid to produce a solution of aluminum sulfate and hydrogen gas. The reaction equation: 2 Al(s) + 3 H2 SO4 (aq) Al2 (SO4 )3 (aq) + 3 H2 (g) How many moles of hydrogen gas and aluminum sulfate solution are produced if 0.5 mol of aluminum is used? Answer: From the reaction equation: 2 Al(s) + 3 H2 SO4 (aq) Al2 (SO4 )3 (aq) + 3 H2 (g) 0.5 mol It is known that the ratio of the coefficients Al : H2 SO4 : Al2 (SO4 )3 : H2 is 2 : 3 : 1 : 3 coefficient H2 Number of moles of hydrogen gas = x mol Al = x o,5 = 0,75 mol Number of moles of aluminum sulfate solution = ( ) = x 0,5 = 0,25 mol x mol So, 2 Al(s) + 3 H2 SO4 (aq) ÿÿÿ Al2 (SO4 )3 (aq) + 3 H2 (g) 0.5 mol 0.25 mol 0.75 mol. 2. 5.6 grams of iron (Ar Fe = 56) is dissolved in hydrochloric acid according to the reaction: 2 Fe(s) + 6 HCl(aq) 2 FeCl3 (aq) + 3 H2 (g) Determine the volume of H2 produced at standard state (STP)! Answer: The volume of H2 at standard state (STP) is: V = n × Vm V = 0.15 mol × 22.4 liter/mol = 3.36 liter 3. As much as 32 grams of calcium carbide (CaC2 ) is dissolved in water to produce gas acetylene (C2 H2 ) according to the reaction: CaC2 (s) + 2 H2 O(l) Ca(OH)2 (s) + C2 H2 (g) Define: a. moles of CaC2 b. mass of Ca(OH)2 produced c. volume of acetylene gas produced under standard conditions (Ar Ca = 40, C = 12, O = 16, and H = 1) Answer: The volume of C2 H2 at standard conditions = n × 22.4 liters/mol = 0.5 mol × 22.4 liters/mol = 11.2 liters Exercise 1. 1. Cement is a mixture of calcium oxide, aluminum, and silicon. Calcium oxide itself is produced from heating calcium carbonate with the equivalent reaction equation: CaCO3 (s) CaO(s) + CO2 (g) If 1 kg of calcium carbonate (CaCO3 ) is heated (Ar Ca = 40, C = 12, O = 16), determine: a. moles and mass of calcium oxide (CaO) produced b. volume of CO2 gas produced at standard conditions (STP) 2. 26.1 grams of MnO2 is reacted according to the reaction equation: MnO2 (s) + 2 NaCl(s) + 2 H2 SO4 (aq) Na2 SO4 (aq) MnSO4 (aq) + 2 H2 O(l) + Cl2 (g) + Determine: a. mol MnO2 (Ar Mn = 55 and O = 16) b. the required mass of NaCl (Ar Na = 23 and Cl = 35.5) c. volume of chlorine gas (Cl2 ) produced at standard conditions (STP) 3. On heating 24.5 grams of KClO3 (ArK = 39, Cl = 35.5, and O = 15) according to the reaction: KClO3 (s) KCl(s) + O2 (g) determine the volume of oxygen gas produced if, at the same temperature and pressure, 0.3 moles of nitrogen gas has a volume of 12 liters! 4. Known reaction: CaCO3 (s) + 2 HCl(aq) CaCl2 (aq) + H2 O(l) + CO2 (g) If 10 grams of limestone (CaCO3 ) (Ar Ca = 40, C = 12, O = 16) is reacted with a hydrochloric acid solution, determine the volume of carbon dioxide gas produced under standard conditions (STP)! 5. In complete combustion of 11 grams of propane (C3 H8 ) according to the reaction: C3 H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2 O(g) how many grams of oxygen are needed? (Ar C = 12, O = 16, and H = 1) 6. Magnesium metal reacts with hydrochloric acid solution according to the following reaction. Mg(s) + 2 HCl(aq) MgCl2 (aq) + 2 H2 (g) How many grams of magnesium (Ar Mg = 24) must be dissolved in hydrochloric acid to produce 2.24 liters of hydrogen gas at standard state (STP)? 7. 4.6 grams of sodium metal is reacted with a solution of copper(II) sulfate (CuSO4 ) according to reaction: 2 Na(s) + CuSO4 (aq) Na2 SO4 (aq) + Cu(s) How many grams of Cu mass are produced? (Ar Na = 23 and Cu = 63.5) 8. In the combustion of 8 grams of sulfur (Ar S = 32) according to the reaction: S(s) + O2 (g) SO2(g) what is the volume of sulfur dioxide gas produced if at the same temperature and pressure, one mole of gas carbon dioxide has a volume of 5 liters