111 Chem Dr. C Doige Adapted from Nigel Eggers (UBCO) Problem Set IV Stoichiometry 1. Balance the following equations: N2O5(g) + H2O(l) HNO3(aq) Mg2C3(s) + H2O(l) Mg(OH)2(s) + C3H4(g) PCl5(l) + H2O(l) H3PO4(aq) + HCl(aq) 2. Balance the following equations: Cr(s) + S8(s) Cr2S3(s) Au2S3(s) + H2(g) Au(s) + H2S(g) NH4ClO4(s) + Al(s) Al2O3(s) + N2(g) + HCl(g) + H2O(g)
3.
The solid fuel in the booster stage of the space shuttle is a mixture of ammonium perchlorate and aluminium powder, which react as follows: NH4ClO4(s) + Al(s) Al2O3(s) + N2(g) + HCl(g) + H2O(g)
Balance the equation. What mass of aluminium should be mixed with 5.0 x 103 kg of ammonium perchlorate?
4.
Camels store the fat tristearin (C57H110O6) in the hump. As well as being a source of energy the fat is a source of water, because when it is used the reaction below takes place. What mass of water is available from 1.0 kg of fat? The equation is not balanced. C57H110O6(s) + O2(g) CO2(g) + H2O(l)
5.
When Xenon difluoride (XeF2) dissolves in water, it slowly reacts with water to produce xenon gas, hydrogen fluoride and oxygen: XeF2(s) + H2O(l) Xe(g) + HF(g) + O2(g)
Which is the limiting reagent when 1.00 g of xenon difluoride is dissolved in 50.0 g of water? What mass of hydrogen fluoride can be produced and how much of the excess reagent remains?
6.
Tin is obtained by heating cassiterite, an ore containing SnO2, with coke. SnO2(s) + 2 C(s) Sn(s) + 2 CO(g) If 24.3 g of Sn(s) is obtained from a 87.5 g sample of cassiterite, calculate the percentage of tin (IV) oxide in the ore. A chemist wishes to find the amount of barium (Ba2+) in 0.2360 g sample. He dissolves the sample in water and precipitates all the barium as barium sulfate (BaSO4) and obtains 0.1326 g of BaSO4. What is the percentage of barium in the sample?
7.
8.
A solution containing 5.0 g of silver nitrate was mixed with another containing 5.0 g of potassium chloride. Which was the limiting reagent for the precipitation of the silver chloride, how much silver chloride was formed and how much of the excess reagent remained?
9.
Chem 111 Dr. C Doige Adapted from Nigel Eggers (UBCO) The theoretical yield of sodium perxenate (Na4XeO6) in a reaction was 1.25 g, but only 1.21 g was obtained. What was the percentage yield of the reaction?
10.
Ammonia reacts with oxygen to produce nitrogen oxide and water, according to the following unbalanced equation: NH3 (g) + O2(g) NO(g) + H2O(l) If 2.00 g of ammonia is reacted with 4.50 g of oxygen a) which is the limiting reagent? b) how much NO is formed? c) what mass of the excess reagent remains at the completion of the reaction?
11.
Barium peroxide, (BaO2), and barium carbonate both decompose on heating: BaO2(s) BaCO3(s) BaO(s) BaO(s) O2(g)
+ + CO2(g)
The reactions are not balanced. If 14.53 g of a mixture of BaO2 and BaCO3 are heated and after decomposition is complete, 12.37 g of BaO remains, what is the composition of the original mixture?
12.
An 11.23 g sample of an ore of copper is crushed, dissolved and the copper precipitated as copper (II) sulphide, which weighed 0.6758 g. What is the percent copper in the ore.
13.
Nitrogen gas (N2) can be prepared by passing gaseous ammonia (NH3) over solid copper (II) oxide at high temperatures. The other products of the reaction are solid copper and water vapour. If 18.1 g of ammonia is reacted with 90.4 g of copper (II) oxide, how many grams of nitrogen gas will be formed and what weight of the excess reagent remains?
14.
A mixture of Mg and Zn having a mass of 1.000 g when burned in oxygen gas (O2) gave a mixture of MgO and ZnO, which had a mass of 1.409 g. What is the percentage of Zn in the mixture?
15.
A student reacts benzene, C6H6, with bromine, Br2, in an attempt to prepare bromobenzene, C6H5Br: C6H6(l) + Br2(l) C6H5Br(l) + HBr(g) What is the theoretical yield of bromobenzene in this reaction when 30.0 g of benzene reacts with 65.0 g of Br2? Which is the limiting reagent and which reagent is in excess? Dibromobenzene, C6H4Br2, is produced as a byproduct in the synthesis of bromobenzene. If the actual yield of bromobenzene was 56.7 g, what is the percentage yield?
16.
A 10.00 mL sample of sulphuric acid (H2SO4) from an automobile battery requires 32.74 mL of 2.15 M NaOH for complete neutralization. What is the concentration of the sulphuric acid? The unbalanced equation is: H2SO4(aq) + NaOH(aq) ...