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PROBLEM 3.42 Potassium Nitrate decomposes on heating, producing potassium oxide and gaseous nitrogen and oxygen. To produce 56.6 Kg of O 2 , how many a.) Moles of KNO 3 and b.) Grams of KNO 3 must be heated? MODIFIED PROBLEM Potassium Nitrate decomposes on heating, producing potassium oxide and gaseous nitrogen and oxygen. To produce 100 Kg of O 2 , how many a.) Moles of KNO 3 and b.) Grams of KNO 3 must be heated? SOLUTION a.) 100 kg O 2 X ((( = 25,000 mole KNO 3 b.) (2,500 mole KNO3) X ( = 252,775 g KNO 3

Solved Problems in Chemistry 2

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PROBLEM 3.42Potassium Nitrate decomposes on heating, producing potassium oxide and gaseous nitrogen and oxygen. To produce 56.6 Kg of O2, how many a.) Moles of KNO3 and b.) Grams of KNO3 must be heated?MODIFIED PROBLEMPotassium Nitrate decomposes on heating, producing potassium oxide and gaseous nitrogen and oxygen. To produce 100 Kg of O2, how many a.) Moles of KNO3 and b.) Grams of KNO3 must be heated?SOLUTIONa.) 100 kg O2 X ((( = 25,000 mole KNO3b.) (2,500 mole KNO3) X ( = 252,775 g KNO3

Problem 3.45Calculate the mass (g) of each product formed when 174 g of silver sulphide reacts with excess hydrochloric acid.Ag2S (s) + HCl (aq) AgCl (s) + H2S (g) [unbalanced]MODIFIED PROBLEMCalculate the mass (g) of each product formed when 200 g of silver sulphide reacts with excess hydrochloric acid.Ag2S (s) + HCl (aq) AgCl (s) + H2S (g) [unbalanced]SOLUTIONAg2S (s) + 2HCl (aq) 2AgCl (s) + H2S (g) [balanced]AgCl Mass = (200g Ag2Cl) ((( Ans: 231.383 g AgClH2S Mass = (200g Ag2Cl) ((( Ans: 25.082 g H2S

PROBLEM 3.60When 20.5 g of methane and 45.0 g of chlorine gas undergo a reaction that has a 70.5% yield, what mass (g) of chloromethane forms? Hydrogen Chloride also forms.MODIFIED PROBLEMWhen 30 g of methane and 50 g of chlorine gas undergo a reaction that has an 80% yield, what mass (g) of chloromethane forms? Hydrogen Chloride also forms.SOLUTIONCH4(g) + Cl2(g)CH3Cl + HCl(30 g CH4l) (( = 1.8703 mole CH3Cl(50 g Cl2) (( = 0.7052 mole CH3Cl- Cl2 is the limiting reactantCH3Cl Mass = (0.7052 moles CH3Cl) ( = 35.59 g CH3Cl(35.59 g CH3Cl) x 80% = 28.478 g CH3Cl

PROBLEM 3.64Butane Gas is compressed and used as a liquid fuel in disposable cigarette lighters and lightweight camping stoves. Suppose a lighter contains 5.50 mL of Butane (d = 0.579g/ml)a.) How many grams of oxygen are needed to burn the butane completely?b.) How many moles of H2O form when all the butane burns?c.) How many total molecules of gas form when the butane burns completely?MODIFIED PROBLEMSuppose a lighter contains 5.50 mL of Butane (d = 0.579g/ml)a.) How many grams of oxygen are needed to burn the butane completely?b.) How many moles of H2O form when all the butane burns?c.) How many total molecules of gas form when the butane burns completely?SOLUTION2C4H10(g) + 13O2(g) 8CO2(g) + H2O (g)a.) (6.00 mL) ((( ( Ans: 12.45 g O2b.) (6.00 mL) (((Ans: 0.299 moles H2O c.) CO2 Moles = (6.00 mL)((( = 0.239 moles CO2Total Moles = 0.299 moles H2O + 0.239 moles CO2

PROBLEM 3.75How many grams of NaH2PO4 are needed to react with 43.74 mL of 0.285 M NaOH.MODIFIED PROBLEMHow many grams of NaH2PO4 are needed to react with 50 mL of 0.300 M NaOH.SOLUTIONNaH2PO4 + 2NaOH Na3PO4 + 2H2ONaOH Moles = (50 mL x ( = 0.015 moles NaOHNaH2PO4 Mass = (0.015 moles NaOH) (( = 0.899 g NaH2PO4