Problem 52
Determine the empirical formulas of the compounds with the following compositions: (a) 2.1 percent \(\mathrm{H}\), 65.3 percent \(\mathrm{O}, 32.6\) percent \(\mathrm{S} ;\) (b) 20.2 percent \(\mathrm{Al}\), 79.8 percent \(\mathrm{Cl}\).
Problem 53
Determine the empirical formulas of the compounds with the following compositions: (a) 40.1 percent \(\mathrm{C}\), 6.6 percent \(\mathrm{H}, 53.3\) percent \(\mathrm{O} ;\) (b) 18.4 percent \(\mathrm{C}\), 21.5 percent \(\mathrm{N}, 60.1\) percent \(\mathrm{K}\)
Problem 54
The empirical formula of a compound is \(\mathrm{CH}\). If the molar mass of this compound is about \(78 \mathrm{~g},\) what is its molecular formula?
Problem 55
The molar mass of caffeine is \(194.19 \mathrm{~g}\). Is the molecular formula of caffeine \(\mathrm{C}_{4} \mathrm{H}_{5} \mathrm{~N}_{2} \mathrm{O}\) or \(\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{~N}_{4} \mathrm{O}_{2} ?\)
Problem 56
Monosodium glutamate (MSG), a food-flavor enhancer, has been blamed for "Chinese restaurant syndrome," the symptoms of which are headaches and chest pains. MSG has the following composition by mass: 35.51 percent C \(, 4.77\) percent \(\mathrm{H}, 37.85\) percent \(\mathrm{O}, 8.29\) percent \(\mathrm{N},\) and 13.60 percent Na. What is its molecular formula if its molar mass is about \(169 \mathrm{~g}\) ?
Problem 58
Chemical analysis shows that the oxygen-carrying protein hemoglobin is 0.34 percent Fe by mass. What is the minimum possible molar mass of hemoglobin? The actual molar mass of hemoglobin is about \(65,000 \mathrm{~g}\). How would you account for the discrepancy between your minimum value and the experimental value?
Problem 61
In combustion analysis, is the combined mass of the products \(\left(\mathrm{CO}_{2}\right.\) and \(\mathrm{H}_{2} \mathrm{O}\) ) less than, equal to, or greater than the combined mass of the compound that is combusted and the \(\mathrm{O}_{2}\) that reacts with it? Explain.
Problem 62
Explain why, in combustion analysis, we cannot determine the amount of oxygen in the sample directly from the amount of oxygen in the products \(\mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{CO}_{2}\)
Problem 63
Menthol is a flavoring agent extracted from peppermint oil. It contains \(\mathrm{C}, \mathrm{H},\) and \(\mathrm{O} .\) In one combustion analysis, \(10.00 \mathrm{mg}\) of the substance yields \(11.53 \mathrm{mg} \mathrm{H}_{2} \mathrm{O}\) and \(28.16 \mathrm{mg} \mathrm{CO}_{2}\). What is the empirical formula of menthol?
Problem 64
Ascorbic acid (vitamin C) contains \(\mathrm{C}, \mathrm{H},\) and \(\mathrm{O} . \mathrm{In}\) one combustion analysis, \(5.24 \mathrm{~g}\) of ascorbic acid yields \(7.86 \mathrm{~g} \mathrm{CO}_{2}\) and \(2.14 \mathrm{~g} \mathrm{H}_{2} \mathrm{O} .\) Calculate the empirical formula and molecular formula of ascorbic acid given that its molar mass is about \(176 \mathrm{~g}\).
