Reactions and Stoichiometry.

Transcription

1 Problem Set Reactions and Stoichiometry. Clearly write answers on separate sheets. Show all work and units. 1. Classify the following chemical reactions according to the categories discussed in class. a) Zn (s) + Ag (aq) Zn( ) (aq) + Ag (s) Single Displacement b) (g) + (g) (g) Synthesis c) acl (aq) + AgC (aq) ac (aq) + AgCl (s) Double Displacement d) Ba(C ) (s) BaC (s) + (g) + C (g) Decomposition e) 1 Al (s) + S (s) Al S (s) Synthesis f) C + 1 C + Combustion. Write and balance the full equation (reactants and products) for the following reactions: a) Combustion of toluene, C C + C + 1 C + C + Toluene is really C I made a mistake on the statement. owever, the answer for both equations is shown. b) Double displacement of carbonic acid and potassium hydroxide. C + K K C + c) Synthesis of zinc sulfide from elemental Zinc and Sulfur, S Zn + S ZnS d) Displacement of nickel metal and nitric acid i + i( ) + e) Decomposition of aluminum carbonate into aluminum oxide and carbon dioxide Al (C ) Al + C

2 f) Synthesis of dinitrogen pentoxide from its elemental gases +. The fermentation of glucose, C, produces ethyl alcohol, C and C : C (aq) C (aq) + C (g) a) ow many moles of C are produced when 0.00 mol of C reacts in this fashion? 0.00mol 0. mol C b) ow many grams of C are needed to form.00 g of C? 10 g C C g g.1g c) ow many grams of C form when.00 g of C are produced? g C C C g C g 1.1g C. Aluminum sulfide reacts with water to form aluminum hydroxide and hydrogen sulfide. a) Write the balanced chemical equation for this reaction. Al S + Al() + S b) ow many grams of aluminum hydroxide are obtained from 10. g of aluminum sulfide? g Al( ) Al( ) Al( ) Al S AlS 10 g Al S 10. g Al S 10. g Al S

3 . Automotive air bags inflate when sodium azide,, rapidly decomposes to its component elements. a) Write and balance the decomposition reaction of sodium azide. a + b) ow many moles of are produced by the decomposition of 1. moles of? 0.00mol 0. mol C c) ow many grams of are required to form.00 g of nitrogen gas? g mol g g. g d) ow many grams of are required to produce 10.0 ft of nitrogen gas if the gas has a density of 1. g/l g mol mol g 1. g 1liter 1liter 10 cm 0.cm 1 ft 10 ft. g. The fizz produced when an Alka-Seltzer tablet is dissolved in water is due to the reaction between sodium bicarbonate, ac, and citric acid C : ac (aq) + C (aq) C (g) + (l) + a C (aq) In a certain experiment 1.00 g of sodium bicarbonate and 1.00 g of citric acid are allowed to react. a) Which reactant is the limiting reactant? Molar Mass ac g/mol Molar Mass C 1 g/mol Converting the mass of reactants to moles: 1g ac 0.011mol ac 1g 0.00 g / mol 1 g / mol The mole ratio for sodium bicarbonate to react with citric acid should be :1 according to the equation.

4 mol ac 0.011mol ac Because the ratio of the moles that we have in the reaction is less than (the ideal ratio) it means that there is less sodium bicarbonate (ac ) than there should be. Therefore, sodium bicarbonate is the limiting reactant. b) ow many grams of carbon dioxide form? g C C mol mol ac ac g ac 1g ac 0. g C c) ow much of the excess reactant remains after the limiting reactant is completely consumed? We need to find how much citric acid is required to react with exactly the amount of sodium bicarbonate (limiting reactant) that we have. 1 g C mol ac ac g ac 1g ac 0. g The amount of citric acid that we have in the reaction is 1 g. The amount of citric acid used in the reaction is 0. g. The unreacted excess will be the difference between the two. 1 g C present in the reaction 0. g C used in the reaction 0. g.. Aspirin, C, is produced from salicylic acid, C, and acetic anhydride, C : C + C C + C a) ow much salicylic acid is required to produce 1.x10 kg of aspirin, assuming that all the salicylic acid is converted to aspirin? 1 g C C C C 10 g 10 g kg kg C 11 kg

5 b) ow much salicylic acid would be required if only 0 percent of the salicylic acid is converted to aspirin? % yield 0% So the reaction proceeds only to 0%. Therefore, we will need more salicylic acid in order to make the desired amount of aspirin. So to find the necessary amount we use the amount obtained in the last question and divide by 0% 11kg kg c) What is the theoretical yield of aspirin if 1 kg of salicylic acid is allowed to react with kg of acetic anhydride? We need to find the limiting reactant. 1,000 g 1 g / mol 10mol,000 g 10 g / mol.mol Because the stoichiometric ratio from the equation is 1:1 it is clear that the acetic anhydride is the limiting reactant. So we must use the amount of acetic anhydride to find the yield of aspirin. 10 g C C 10 g 10 g kg C 1kg 0. kg d) If the situation described in part (c) produces 1 kg of aspirin, what is the percentage yield? Actual yield 1 kg % yield 0..% yield theoretical yield 0. kg