74. What is the percent by mass of hydrogen in aspirin, CHO?
75. Calculate the molecular formulas of the compounds having the following empirical formulas and molar masses: CH, 58 g/mol; CH, 78 g/mol; and HgCl, 236.1 g/mol.
76. Give three examples of methods of measuring the amount of something, and give an example of how one of these quantities can be converted to another type of quantity.
77. When determining the moles of a gas from the volume of that gas, why is it important that the volume be measured at STP?
78. Why is it possible to calculate the density of a gas at STP, knowing only its molar mass, but it is not possible to make the same calculation for a solid or a liquid?
79. The percentage composition of a polymer used for the non-stick surfaces of cooking utensils is 24% C and 76% F by mass. Explain the steps in determining the empirical formula of the polymer.
80. The density of acetylene at STP is 1.17 g/L. The empirical formula of acetylene is CH. Describe how you can determine the molar mass of acetylene and its molecular formula if you know only its density at STP and its empirical formula.