Stoichiometry: Limiting Reagent Calculations

Limiting Reagent In a chemical reaction, the mole ratio of the reactants added is not always the same as the ratio of the reaction coefficients. This causes the reactants to run out to react first. Such a reactant is called the limiting reagent. Example 1. 1. One mole of sodium hydroxide (NaOH) solution is reacted with 1 mole of acid solution sulfate (H2 SO4 ) according to the reaction: 2 NaOH(aq) + H2 SO4 (aq) Na2 SO4 (aq) + 2 H2 O(l) Determine: a. limiting reagent b. remaining reagent c. moles of Na2SO4 and moles of H2O are produced Answer: a. The moles of each substance are divided by the coefficient, then choose the small quotient as the limiting reagent Answer: b. The remaining reactant is H2 SO4 c. Moles of Na2 SO4 produced = 0.5 mol mol of H2 SO4 produced = 1 mol 2. 100 mL of 0.1 M Ca(OH)2 solution is reacted with 100 mL of 0.1 M HCl solution according to reaction: Ca(OH)2 (aq) + 2 HCl(aq) Determine the limiting reactant! Answer: CaCl2 (aq) + 2 H2 O(l) So, the limiting reagent is HCl solution. Exercise 1. 1. 0.5 mol Mg(OH)2 reacts with 0.5 mol HCl according to the reaction equation: Mg(OH)2 (aq) + 2 HCl(aq) MgCl2 (aq) + 2 H2 O(l) Determine: a. limiting reagent b. remaining reagent c. moles of MgCl2 and moles of H2O 2. 100 mL of 0.2 M NaOH solution reacts with 100 mL of 0.1 M HCl solution according to the reaction equation: NaOH(aq) + HCl(aq) Determine: a. limiting reagent b.residual reagent c. moles of NaCl 3. NaCl(aq) + HCl(aq) 5.4 grams of aluminum metal (Ar Al = 27) is reacted with 24.5 grams of H2 SO4 (Ar H = 1, S = 32, and O = 16). The equation for the reaction: 2 Al(s) + 3 H2 SO4 (aq) Al2 (SO4 )3 (aq) + 3 H2 (g) Determine: a. limiting reagent b. remaining moles of reagent c. volume of H2 gas at standard state (STP) 4. 3.2 grams of methane (CH4 ) is burned with 16 grams of oxygen. The reaction equation: CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2 O(l) Determine: a. limiting reagent b. the mass of CO2 gas formed (Ar C = 12, O = 16, and H = 1) 5. 100 mL of 0.1 M KOH solution is reacted with 100 mL of 0.2 M HCl solution. The reaction equation: KOH(aq) + HCl(aq) KCl(aq) + H2 O(l) What mass of KCl is formed? (Ar K = 39 and Cl = 35.5). 6. The lead(II) nitrate solution is reacted with the KI solution according to the reaction: Pb(NO3 )2 (aq) + 2 KI(aq) PbI2 (s) + 2 KNO3 (aq) Determine the mass of PbI2 (Ar Pb = 207 and I = 127) that is formed, when reacted: a. 50 mL of 0.1 M Pb(NO3 )2 solution and 50 mL of 0.1 M KI solution b. 50 mL of 0.1 M Pb(NO3 )2 solution and 100 mL of 0.1 M KI solution c. 50 mL of 0.2 M Pb(NO3 )2 solution and 400 mL of 0.1 M 7 KI solution. d. 100 mL of 0.2 M KCl solution was reacted with 200 mL of 0.05 M AgNO3 solution. 7. The equation for the reaction: KCl(aq) + AgNO3 (aq) AgCl(s) + KNO3 (aq) What mass of AgCl is produced (Ar Ag = 108, Cl = 35.5)? 8. A total of 20 grams of CaCO3 is dissolved in 1 liter of 0.2 M hydrochloric acid according to the reaction equation: CaCO3 (s) + 2 HCl(aq) CaCl2 (aq) + CO2 (g) + H2 O(l) a. a. Determine the mass of CaCl2 formed (Ar Ca = 40, Cl = 35.5, C = 12, and O =16)! b. How many liters of carbon dioxide gas are produced when measured at the same temperature and pressure when 2 liters of NO gas (Ar N = 14 and O = 16) have a mass of 1.2 grams? 9. Carbon is burned according to the reaction equation: 2 C(s) + O2 (g) 2 CO(g) How many grams of CO can be produced when 6 grams of carbon is burned with 32 grams of oxygen? (Ar C = 12 and O = 16) 10. As much as 8.1 grams of aluminum metal reacted with 38 grams of Cr2 O3 (Ar Al = 27, Cr = 52, and O = 16) according to the reaction equation: 2 Al(s) + Cr2 O3 (aq) Al2 O3 (aq) + 2 Cr(s) How many grams of chromium metal are produced? 11. AgNO3 solution reacts with MgCl2 solution to form AgCl precipitate according to the reaction equation: 2 AgNO3 (aq) + MgCl2 (aq) Mg(NO3 )2 (aq) + 2 AgCl(s) Calculate the mass of the precipitate formed, if reacted: a. 100 mL of 0.2 M AgNO3 solution with 100 mL of 0.2 M MgCl2 solution b. 200 mL of 0.2 M AgNO3 solution with 100 mL of 0.2 M MgCl2 solution c. 200 mL of 0.2 M AgNO3 solution with 100 mL of 0.1 M MgCl2 solution 12. Superphosphate fertilizer (Ca(H2 PO4 )2 ) is prepared by reacting calcium phosphate with sulfuric acid solution. The reaction equation: Ca3 (PO4 )2 + 2 H2 SO4 Ca(H2 PO4 ) 2 (s) + 2 CaSO4 (aq) Determine the mass of superphosphate fertilizer (Ca(H2) which is formed when reacted 1.860 (PO4 ) grams Ca3 10 liters of H2 SO4 1 M? (Ar Ca = 40, H = 1, P = 31, and O = 32