Problem 68
Aluminum is a lightweight metal (density \(\left.=2.70 \mathrm{~g} / \mathrm{cm}^{3}\right)\) used in aircraft construction, high-voltage transmission lines, beverage cans, and foils. What is its density in \(\mathrm{kg} / \mathrm{m}^{3} ?\)
Problem 69
The density of ammonia gas under certain conditions is \(0.625 \mathrm{~g} / \mathrm{L} .\) Calculate its density in \(\mathrm{g} / \mathrm{cm}^{3}\).
Problem 70
(a) Carbon monoxide (CO) is a poisonous gas because it binds very strongly to the oxygen carrier hemoglobin in blood. A concentration of \(8.00 \times 10^{2}\) ppm by volume of carbon monoxide is considered lethal to humans. Calculate the volume in liters occupied by carbon monoxide in a room that measures \(17.6 \mathrm{~m}\) long, \(8.80 \mathrm{~m}\) wide, and \(2.64 \mathrm{~m}\) high at this concentration.
Problem 71
The average time it takes for a molecule to diffuse a distance of \(x \mathrm{~cm}\) is given by $$ t=\frac{x^{2}}{2 D} $$ where \(t\) is the time in seconds and \(D\) is the diffusion coefficient. Given that the diffusion coefficient of glucose is \(5.7 \times 10^{-7} \mathrm{~cm}^{2} / \mathrm{s},\) calculate the time it would take for a glucose molecule to diffuse \(10 \mu \mathrm{m}\), which is roughly the size of a cell.
Problem 72
A human brain weighs about \(1 \mathrm{~kg}\) and contains about \(10^{11}\) cells. Assuming that each cell is completely filled with water (density \(=1 \mathrm{~g} / \mathrm{mL}\) ), calculate the length of one side of such a cell if it were a cube. If the cells are spread out into a thin layer that is a single cell thick, what is the surface area in square meters?
Problem 75
Which of the following statements describe physical properties and which describe chemical properties? (a) Iron has a tendency to rust. (b) Rainwater in industrialized regions tends to be acidic. (c) Hemoglobin molecules have a red color. (d) When a glass of water is left out in the sun, the water gradually disappears. (e) Carbon dioxide in air is converted to more complex molecules by plants during photosynthesis.
Problem 76
In determining the density of a rectangular metal bar, a student made the following measurements: length, \(8.53 \mathrm{~cm} ;\) width, \(2.4 \mathrm{~cm} ;\) height, \(1.0 \mathrm{~cm} ;\) mass, \(52.7064 \mathrm{~g}\). Calculate the density of the metal to the correct number of significant figures.
Problem 77
Calculate the mass of each of the following: (a) a sphere of gold with a radius of \(10.0 \mathrm{~cm}\) (volume of a sphere with a radius \(r\) is \(V=4 / 3 \pi r^{3} ;\) density of gold \(=19.3 \mathrm{~g} / \mathrm{cm}^{3}\) ), (b) a cube of platinum of edge length \(0.040 \mathrm{~mm}\) \(\left(\right.\) density \(\left.=21.4 \mathrm{~g} / \mathrm{cm}^{3}\right)\), (c) \(50.0 \mathrm{~mL}\) of ethanol \((\) density \(=0.798 \mathrm{~g} / \mathrm{mL})\).
Problem 78
A cylindrical glass tube \(12.7 \mathrm{~cm}\) in length is filled with mercury (density \(=13.6 \mathrm{~g} / \mathrm{mL}\) ). The mass of mercury needed to fill the tube is \(105.5 \mathrm{~g}\). Calculate the inner diameter of the tube (volume of a cylinder of radius \(r\) and length \(h\) is \(V=\pi r^{2} h\) ).
Problem 79
The following procedure was used to determine the volume of a flask. The flask was weighed dry and then filled with water. If the masses of the empty flask and filled flask were \(56.12 \mathrm{~g}\) and \(87.39 \mathrm{~g}\), respectively, and the density of water is \(0.9976 \mathrm{~g} / \mathrm{cm}^{3},\) calculate the volume of the flask in cubic centimeters.
