Chapter 7

Consider the reaction: 4 K(s) + O2(g)-2 K2O(s) The molar mass of K is 39.09 g>mol and that of O2 is 32.00 g>mol. Without doing any calculations, choose the conditions under which potassium is the limiting reactant and explain your reasoning. a. 170 g K, 31 g O2 b. 16 g K, 2.5 g O2 c. 165 kg K, 28 kg O2 d. 1.5 g K, 0.38 g O2

Consider the reaction: 2 NO(g) + 5 H2(g)-2 NH3(g) + 2 H2O(g) A reaction mixture initially contains 5 moles of NO and 10 moles of H2. Without doing any calculations, determine which set of amounts best represents the mixture after the reactants have reacted as completely as possible. Explain your reasoning. a. 1 mol NO, 0 mol H2, 4 mol NH3, 4 mol H2O b. 0 mol NO, 1 mol H2, 5 mol NH3, 5 mol H2O c. 3 mol NO, 5 mol H2, 2 mol NH3, 2 mol H2O d. 0 mol NO, 0 mol H2, 4 mol NH3, 4 mol H2O

Imagine you mix 16.05 g of methane (CH4) gas and 96.00 g of oxygen (O2) gas and then ignite the mixture. After a bright flash and a loud bang, some water droplets form on the inside of the reaction vessel. a. Write the balanced chemical reaction for the combustion of methane. b. Sketch the process that occurred in the vessel using circles to represent atoms. Represent carbon with black circles, hydrogen with white circles, and oxygen with red circles. Let one circle (or one molecule made of circles bonded together) represent exactly one mole. c. How many moles of water can you make? How many moles of carbon dioxide? d. Will anything be left over? What? How much? e. Identify the following: limiting reactant, reactant in excess, and theoretical yield.