Problem 121
Nicotine, a stimulant found in tobacco, has the mass percent composition: C, 74.03%; H, 8.70%; N, 17.27%. The molar mass of nicotine is 162.26 g/mol. Find the molecular formula of nicotine.
Problem 122
Estradiol is a female sexual hormone that causes maturation and maintenance of the female reproductive system. Elemental analysis of estradiol gave the mass percent composition: C, 79.37%; H, 8.88%; O, 11.75%. The molar mass of estradiol is 272.37 g/mol. Find the molecular formula of estradiol
Problem 123
A sample contains both KBr and KI in unknown quantities. If the sample has a total mass of 5.00 g and contains 1.51 g K, what are the percentages of KBr and KI in the sample by mass?
Problem 124
A sample contains both CO2 and Ne in unknown quantities. If the sample contains a combined total of 1.75 mol and has a total mass of 65.3 g, what are the percentages of CO2 and Ne in the sample by mole?
Problem 127
An iron ore contains 38% Fe2O3 by mass. What is the maximum mass of iron that can be recovered from 10.0 kg of this ore?
Problem 129
You can use the concepts in this chapter to obtain an estimate of the number of atoms in the universe. These steps will guide you through this calculation. (a) Begin by calculating the number of atoms in the sun. Assume that the sun is pure hydrogen with a density of 1.4 g>cm3 . The radius of the sun is 7 * 108 m, and the volume of a sphere is V = 4 3pr3 . (b) The sun is an average-sized star, and stars are believed to compose most of the mass of the visible universe (planets are so small they can be ignored), so we can estimate the number of atoms in a galaxy by assuming that every star in the galaxy has the same number of atoms as our sun. The Milky Way galaxy is believed to contain 1 * 1011 stars. Use your answer from part a to calculate the number of atoms in the Milky Way galaxy (c) Astronomers estimate that the universe contains approximately 1 * 1011 galaxies. If each of these galaxies contains the same number of atoms as the Milky Way galaxy, what is the total number of atoms in the universe?
Problem 130
. Because of increasing evidence of damage to the ozone layer, chlorofluorocarbon (CFC) production was banned in 1996. However, about 100 million auto air conditioners still use CFC-12 (CF2Cl2). These air conditioners are recharged from stockpiled supplies of CFC-12. If each of the 100 million automobiles contains 1.1 kg of CFC-12 and leaks 25% of its CFC-12 into the atmosphere per year, how much Cl in kilograms do auto air conditioners add to the atmosphere each yea
Problem 131
1\. In 1996, the media reported that possible evidence of life on Mars was found on a meteorite called Allan Hills 84001 (AH 84001). The meteorite was discovered in Antarctica in 1984 and is believed to have originated on Mars. Elemental analysis of substances within its crevices revealed carbon-containing compounds that normally derive only from living organisms. Suppose that one of those compounds had a molar mass of 202.23 g/mol and the mass percent composition: C, 95.02%; H, 4.98%. What is the molecular formula for the carbon-containing compound?
Problem 133
. Imagine that all our balances displayed mass in units of slugs instead of grams. Would we still want to use the number 6.022 * 1023 for Avogadro’s number? Why or why not? If not, what number would we want to use instead? (A slug is equal to 14,954 g.)
