3In stoichiometry, chemists are mainly concerned with Multiple ChoiceIn stoichiometry, chemists are mainly concerned withA. the types of bonds found in compounds.B. mass relationships in chemical reactions.C. energy changes occurring in chemical reactions.D. the speed with which chemical reactions occur.
5What do the coefficients in a chemical equation tell you?
6Multiple ChoiceAssume ideal stoichiometry in the reaction: CH4 + 2O2 CO2 + 2H2OIf you know the mass of CH4, you can calculateA. only the mass of CO2 produced.B. only the mass of O2 reacting.C. only the mass of CO2 + H2O produced.D. the mass of O2 reacting & CO2 + H2O produced.
7Which properties must be the same on both sides of a chemical equation?
8Which properties don’t have to be the same on both sides of a chemical equation?
16What is the Limiting Reactant. 2C2H6 + 7O2 4H2O + 6CO2 7. 49 mol 24 What is the Limiting Reactant? 2C2H6 + 7O2 4H2O + 6CO mol mol
17Multiple Choice 2Na + Cl2 2NaCl What mass of NaCl can be produced by the reaction of 0.75 mol Cl2?2Na + Cl2 2NaClA g C. 44 gB. 1.5 g D. 88 g
18Why is the LR not necessarily the reactant with the least amount of moles?
19Multiple Choice CaCO3 CaO + CO2 What mass of CO2 can be produced from 25.0 g CaCO3 given the decomposition reactionCaCO3 CaO + CO2A g C gB g D g
20How many moles of each product can be formed How many moles of each product can be formed? 2C2H O2 4H2O + 6CO mol mol
21Multiple ChoiceIf a chemical reaction involving substances A and B stops when B is completely used up, then B is referred to as theA. excess reactant.B. primary reactant.C. limiting reactant.D. primary product.
22How many grams of water can be formed. 2C2H6 + 7O2 4H2O + 6CO2 7 How many grams of water can be formed? 2C2H6 + 7O2 4H2O + 6CO mol mol
23Multiple ChoiceIf a chemist calculates the maximum amount of product that could be obtained in a chemical reaction, he or she is calculating theA. percentage yield.B. mole ratio.C. theoretical yield.D. actual yield.
24How many moles excess reactant remain after the reaction How many moles excess reactant remain after the reaction? 2C2H O 4H2O + 6CO mol mol
25Short AnswerWhat data are necessary to calculate the percentage yield of a reaction?
26Extended ResponseA student makes a compound in the laboratory and reports an actual yield of 120%. Is this result possible? Assuming that all masses were measured correctly, give an explanation.
27Extended ResponseBenzene, C6H6, and hydrogen bromide, HBr, as shown below. When 40.0 g of benzene are reacted with 95.0 g of bromine, 65.0 g of bromobenzene is produc with bromine, Br2, to produce bromobenzene, C6H5BrC6H6 + Br2 C6H5Br + HBra. Which compound is the limiting reactant? b. What is the theoretical yield of bromobenzene? c. What is the reactant in excess, and how much remains after the reaction is completed? d. What is the percentage yield?