Chemical Quantities. Conversion factors. Definition of mole. 1 mole = x items. (Example)

Transcription

1 Chemical Quantities Definition of mole Conversion facts 1 mole = items (Eample 1 mole of carbon atoms = carbon atoms (number to mole 1mole C atoms C atoms (mole to number C atoms 1mole C atoms 1 mole of NaCl fmula units = NaCl fmula units 1mole NaCl NaCl mole NaCl NaCl Sample Problems 1. How many sodium atoms are in.45 moles of sodium? i given:.45 moles of Na wanted: # Na ii plan: mole of Na # Na.45 moles Na #Na 1 mole Na = #Na definition of mole. How many moles of CO are contained in CO molecules? i given: CO wanted: moles CO ii plan: #CO molecules mole CO CO 1 mole CO #CO = 40.7 moles CO definition of mole 1

2 Molar mass of atoms (= mass of 1 mole of atoms 1 mole of atoms = mass (in grams of atoms of an element (Eample In the periodic table element of carbon is shown as below. 6 C 1.01 This indicates one mole of carbon has a mass of 1.01 g of carbon atoms. Therefe, 1 mole of C atoms = 1.01 g of C atoms (mass to mole (mole to mass 1mole C 1.01g C 1.01 g C 1mole C Sample problems A jewelry contains moles of silver metal. How many grams of silver metal does the jewelry contain? i given: moles Ag wanted: g Ag ii plan: mole Ag g Ag moles Ag g Ag 1 mole Ag = 4.85 g Ag molar mass of Ag

3 Mole ratio and molar mass of compounds (Eample 1 1 mole of CO = 1 mole (C + O = 1 mole C + moles O Molar mass of CO can be calculated as 1 mole C = 1.01 g + moles of O = g =.00 g g CO Therefe, 1 mole of CO = g CO (Molar ratio 1mole CO 1mole C 1mole C 1mole CO 1mole CO moles O 1mole CO 44.01g CO moles O 1mole CO (Molar mass 44.01g CO 1mole CO (Eample 1mole Ca (Molar ratio 1mole Ca 1 mole of Ca(NO = 1 mole (Ca + N + 6O = 1 mole Ca + moles N + 6 moles O moles N moles N Molar mass of Ca(NO can be calculated as 1 mole of Ca = g moles of N = g = 8.0 g + 6 moles of O = = g g Ca(NO 6 moles O 6 moles O (Molar mass g Ca(NO g Ca(NO

4 Sample Problems 1. How many moles oygen atoms are contained in 0.15 moles of Al (SO 4? i given: 0.15 moles Al (SO 4 wanted: moles O ii plan: mole Al (SO 4 mole O Problem solving: 0.15 mole Al (SO 4 1 moles O = 1.50 moles O 1 mole Al (SO 4. What is the mass (in grams of mole of Mg(OH? i given: mole Mg(OH wanted: g Mg(OH ii plan: mole Mg(OH g Mg(OH mole Mg(OH 58. g Mg(OH = 1.05 g Mg(OH 1 mole Mg(OH molar mass* *molar mass of Mg(OH : + 1 mole of Mg = 4.1 g moles of O = =.00 g moles of H = 1.01 g =.0 g 58. g 4

5 Chemical equations f reactions H + O H O (Mole ratio moles H : 1 mole O : moles H O (Mole ratio 1mole H 1mole O 1mole O 1mole H 1mole O 1mole H O 1mole H O 1mole O 1mole H 1mole H O 1mole H O 1mole H Sample Problems 1. How many moles of carbon dioide will be produced if.48 moles of propane gas (C H 8 reacted with oygen gas (=combustion of propane gas? C H 8 + 5O CO + 4H O i given:.48 moles C H 8 wanted: moles CO ii plan: mole C H 8 mole CO.48 moles C H 8 moles CO = 10.4 moles CO 1 mole C H 8 (from coefficients in reaction equation 5

6 Eercises 1. How many moles of NaCl are in fmula units of NaCl?. Calculate the molar mass of calcium hydroide, Ca(OH.. What is the mass (in grams of 4.55 moles of oygen gas (O? 4. How many moles of copper (Cu are present in grams of copper? 6

7 5. How many moles of oygen atoms are in 0.00 g of Mg(OH (antiacid, laative? 6. How many sulfur atoms are in 0.15 mole of Al (SO 4 (antiperspirant? 7. How many sulfur atoms are present in 5.50 g of carbon disulfide (CS? 8. Iron metal reacts with oygen gas to produce nitrogen iron(iii oide. a Write a balanced chemical equation. b Write the mole-mole conversion facts ( between the pairs below. Iron and oygen gas: 7

8 Iron and iron(iii oide: Oygen and iron(iii oide: 9. Complete combustion of propane gas (C H 8 produces carbon dioide and water. a Write a balanced chemical equation. b How many moles of carbon dioide will be produced if 1.0 g of propane gas reacted with ecess amount of oygen gas? 10. How many moles of HCl gas can be obtained by reacting 11.5 g of hydrogen gas with 45.8 g of chline gas? Which substance is the limiting reactant? H (g + Cl (g HCl (g First, the amount of product (in moles that can be produced from each reactant. Then, identify the limiting reactant. Reactant that gives the least amount of product is the limiting reactant. 8

9 Answer key to Eercises 1. How many moles of NaCl are in fmula units of NaCl? i given: # NaCl wanted: mole NaCl ii plan: # NaCl mole NaCl # NaCl 1 mole NaCl = 76 moles NaCl # NaCl definition of mole. Calculate the molar mass of calcium hydroide, Ca(OH. 1 mole Ca(OH contains 1 mole Ca, moles O, and moles H. Therefe, 1 mole Ca = g = g + moles O = g =.00 g moles H = 1.01 =.0 g g = molar mass of Ca(OH. What is the mass (in grams of 4.55 moles of oygen gas (O? i given: mole O wanted: g O ii plan: mole O g O 4.55 moles O.00 g O = 146 g O ( g O 1 mole O molar mass of O 9

10 4. How many moles of copper (Cu are present in grams of copper? i given: grams Cu wanted: mole Cu ii plan: g Cu mole Cu g Cu 1 mole Cu 6.55 g Cu = mole Cu ( mole Cu molar mass of Cu 5. How many moles of oygen atoms are in 0.00 g of Mg(OH (antiacid, laative? i given: 0.00 g Mg(OH wanted: moles O ii plan: g Mg(OH moles Mg(OH moles O 0.00 g Mg(OH 1 mole Mg(OH 58. g Mg(OH mole O 1 mole Mg(OH = mole O molar mass of Mg(OH 6. How many sulfur atoms are in 0.15 mole of Al (SO 4 (antiperspirant? i given: 0.15 mole Al (SO 4 wanted: # of S atoms ii plan: mole Al (SO 4 mole S # S 0.15 mole Al (SO 4 mole S 1 mole Al (SO # S 1 mole S = # S atoms definition of mole 10

11 7. How many sulfur atoms are present in 5.50 g of carbon disulfide (CS? i given: 5.50 g CS wanted: # S ii plan: g CS mole CS mole S # S 5.50 g CS 1 mole CS mole S 76.1 g CS 1 mole CS # S 1 mole S = # S atoms molar mass definition of mole 8. Iron metal reacts with oygen gas to produce iron(iii oide. a Write a balanced chemical equation. 4Fe (s + O (g Fe O (s b Write the mole-mole conversion facts ( between the pairs below. Iron and oygen gas: 4 moles Fe mole O mole O 4 moles Fe Iron and iron(iii oide: 4 moles Fe moles Fe O moles Fe O 4 moles Fe Oygen and iron(iii oide: mole O moles Fe O moles Fe O mole O 11

12 9. Complete combustion of propane gas (C H 8 produces carbon dioide and water. a Write a balanced chemical equation. C H 8 + 5O CO + 4H O b How many moles of carbon dioide will be produced if 1.0 g of propane gas reacted with ecess amount of oygen gas? i given: 1.0 g C H 8 wanted: mole CO ii plan: g C H 8 mole C H 8 mole CO 1.0 g C H 8 1 mole C H 8 mole CO g C H 8 1 mole C H 8 = mole CO molar mass 10. How many moles of HCl gas can be obtained by reacting 11.5 g of hydrogen gas with 45.8 g of chline gas? Which substance is the limiting reactant? H (g + Cl (g HCl (g First, the amount of product (in moles that can be produced from each reactant. Then, identify the limiting reactant. Reactant that gives the least amount of product is the limiting reactant. i given: 0.5 g H wanted: mole HCl plan: g H mole H mole H 11.5 g H mole HCl 1 mole H.0 g H 1 mole H = 11.4 moles HCl molar mass 1

13 ii given: 45.8 g Cl wanted: mole HCl plan g Cl mole Cl mole HCl 45.8 g Cl mole HCl 1 mole Cl g Cl 1 mole Cl = 1.9 moles HCl molar mass From the comparison of moles of HCl from i and ii, reactant Cl gives less amount of moles of HCl than other reactant H. 1.9 moles HCl < 11.4 moles HCl Therefe, Cl is a limiting reactant. 1