PERIODIC TABLE. mass of crucible + zinc (before heating) = g mass of crucible + oxide (after heating) = g

Transcription

1 PERIODIC TABLE 1. Glycerol (C H 8 O ) is sold in drug stores as glycerine and is commonly found in soaps and shampoos. a) What is the molar mass of glycerol? b) What is the mass in grams of 1.00 mole of glycerol? c) How many molecules are in one mole of glycerol? d) How many grams are in 0.17 moles of glycerol?. Ammonia (NH ) is the active ingredient in many kitchen cleansers. How many atoms are in a) one molecule of ammonia? b) one mole of ammonia? c).40 grams of ammonia?. Sodium nitrite is a controversial food preservative added to processed meat and thought to form cancer-causing compounds when heated. What are the mass percentages of each element in sodium nitrite? 4. A compound consists of 40.7% C, 5.1% H, and 54.% O? a) What is its empirical formula? b) The molar mass of this compound is 118 grams/mole. What is the molecular formula of this compound? 5. A 5.0 gram sample of a compound made up of magnesium, carbon and oygen contains 7.0 grams magnesium and.55 grams carbon. a) Find the empirical formula of this compound. b) Find the mass percentage of each element in this compound. c) What is the mass of magnesium in a 1.9 gram sample of this compound? d) What is the mass of this compound that contains 0.90 moles of carbon? 6. A sample of zinc is heated in air to form zinc oide. Assuming all of the zinc is converted to the oide, use the data table below to calculate the empirical formula of zinc oide. mass of crucible =.00 g mass of crucible + zinc (before heating) =.64 g mass of crucible + oide (after heating) = 4.04 g 7. Balance the following equations: a) the combustion of the rocket fuel diborane, B H 6 (l) + O (g) B O (s) + H O(l) b) the combustion of the poisonous gas, PH, PH (g) + O (g) H O(l) + P 4 O 10 (s) 8. Write a balanced equation for each of the following reactions:

2 a) the reaction of solid lithium with nitrogen to form solid lithium nitride. b) the reaction between aqueous solutions of cobalt(iii) nitrate and sodium hydroide to form aqueous sodium nitrate and solid cobalt(iii) hydroide. c) the reaction between solid zinc and aqueous hydrochloric acid in a single replacement reaction. d) classify the reactions in (a) and (b). 9. Hydrogen sulfide, given off by decaying organic matter, is converted to sulfur dioide in the atmosphere by the reaction: H S(g) + O (g) SO (g) + H O(l) a) How many moles of H S are required to form 8.0 moles of SO? b) How many grams of O are required to react with 1.00 mole of H S? c) How many grams of water are produced from 6.8 g H S? d) If 1.0 grams of SO are formed from 7.98 g of H S, what is the percent yield? e) How many grams of SO are produced starting from.66 g H S and.0? Which reactant is limiting? 10. A gaseous miture containing 7.50 mol H (g) and 9.00 mol Cl (g) reacts to form hydrogen chloride (HCl) gas. a) Write a balanced equation for the reaction. b) Which reactant is limiting? c) If all the limiting reactant is consumed, how many moles of hydrogen chloride are formed? d) How many moles of the ecess reactant remain unreacted?

3 ANSWERS 1. a) (1.0) + 8(1.01) + (0) = 9.1 g/mole b) 9.1 g c) molecules 9. 1 g d) 0.17 moles 1 mole = 0.0 g. a) 4 atoms (one N + H) b) 1 mole NH molecules 1 mole NH 1 4 atoms molecule = atoms 1 mole NH c).40 g NH g NH molecules 4 atoms mole NH 1 molecule = atoms. Molar mass of NaNO = (0) = 69.0 g/mole % Na =.0/69.0 =.% Na; % N = 14.0/69.0 = 0.% N; %O = (0)/69.0 = 46.4% O.% Na, 0.% N and 46.4% O. 4. a) In 100 g of this compound, there are 40.7 g C, 5.1 g H, and 54. g O 40.7 g C 1 mole C =.9 moles C.9/.9 = 1 = 1. 0 g C 5.1 g H 1 mole H 1. 0 g H 54. g O 1 mole O empirical formula = CHO = 5.1 moles H 5.1/.9 = 1.5 = =.9 moles O.9/.9 = 1 = b) Molar mass of C H O = (1.0) + (1.0) + (0) = 59.0 g/mole 118/59.0 = molecular formula = C4H6O4 5. a) In 5.0 g of compound, there are 7.0 g Mg,.55 g C and 5.0-( ) = 14.5 g O. 7.0 g Mg 1 mole Mg = 0.96 moles Mg 0.96/0.96 = 1 4. g Mg.55 g C 1 mole C = 0.96 moles C 0.96/0.96 = g C 14.5 g O 1 mole O formula = MgCO = moles O 0.891/0.96 = b) % Mg = 7.0/5.0 = 8.8% Mg; %C =.55/5.0 = 14. % C; % O = 14.5/5.0 = 57.0% O. (You should get the same result using molar mass and atomic masses.)

4 c) 1.9 g compound 8. 8 g Mg 100 g compound = 4.00 g Mg 1. 0 g C d) 0.90 mol C 1 mole C g compound = 4.5 g compound 14. g C 6. mass of Zn =.64 g -.00 g = 1.64 g Zn mass of O = 4.04 g -.64 g = 0.4. # moles Zn: 1.64 g Zn 1 mole Zn = moles Zn 0.51/0.5 = g Zn # moles O: mole O formula = ZnO = 0.05 moles O 0.5/0.5 = 1 7. a) B H 6 (l) + O (g) B O (s) + H O(l) b) 4 PH (g) + 8 O (g) 6 H O(l) + P 4 O 10 (s) 8. a) 6 Li(s) + N (g) Li N(s) b) Co(NO ) (aq) + NaOH(aq) NaNO (aq) + Co(OH) (s) c) Zn(s) + HCl(aq) ZnCl (aq) + H (g) d) (a) is a combination (synthesis) reaction. (b) is a double replacement reaction. mol H S 9. a) 8.0 moles SO = 8.0 moles HS mol SO b) 1.00 mole H S c) 6.8 g H S d) 7.98 g H S mol O mol H 1 mol H S 4.1 g H S 1 mol H S 4.1 g H S S. 1 mol O mol H O mol H S mol SO mol H S = g H O 1 mol H O 64.1 g SO 1 mol SO actual yield 1.0 g SO % yield = 100% 100% theoretical yield 15.0 g SO =.60 g HO = 15.0 g SO = 80.0% 1 mol HS mol SO 64.1 g SO e).66 g H S 4.1 g HS 1 mol O mol SO 64.1 g SO.0 = 4.01 g SO. mol O 1 mol SO O is limiting; 4.01 g SO is produced = 5.00 g SO mol HS 1 mol SO 10. a) H (g) + Cl (g) HCl(g) b) H is limiting (H and Cl react in a ratio 1:1 ratio and there is less H.) c) 7.50 mol H mol HCl 1 mol H = 15.0 mol HCl

5 d) = 1.50 mol Cl left