Steel is an alloy consisting of Fe with a small amount of C. Elemental Cr can be added to steel to make the steel less likely to rust; Cr atoms react with oxygen in the air to form a nonreactive layer of chromium oxide on the surface of the steel, preventing oxidation of underlying Fe atoms.   A sample of steel-chromium alloy contains 15 percent Cr by mass. Which of the following diagrams best shows a particle-level view of a surface section and an interior section of the alloy represented in the diagram? (The atomic radii of the atoms involved are given in the accompanying table.)   Table: Molar Masses and Atomic Radii of Element Molar Mass (g/mol) Atomic Radius (pm) Fe 55.85 125 Cr 52.00 127 C 12.01 77 O 16.00 73

The figure represents three sealed 1.0 L vessels, each containing a different inert gas at 298 K. The pressure of Ar in the first vessel is 2.0 atm. The ratio of the numbers of Ar, Ne, and He atoms in the vessels is 2:1:6, respectively. After all the gases are combined in a previously evacuated 2.0 L vessel, what is the total pressure of the gases at 298 K? A diagram shows the combining of three gases collected in three sealed 1 liter vessels. The first vessel contains A r at 2 atm. The vessel has four atoms. Plus. The second vessel contains N e. The vessel has two bigger atoms. The third vessel contains H e. The vessel has 12 smaller atoms. The resultant 2 liter vessel is left blank.

A sample of C4H10(g) is placed in a rigid vessel with a movable piston. The volume of the gas is reduced by moving the piston downward while the temperature is maintained at 25°C, as shown in the figure. The figure shows two containers equipped with a moveable piston. A sample of C 4 H 10 gas is inside each container. In the first container, the piston is near the top of the container and the C 4 H 10 occupies a volume of 0.50 liter. The piston in the second container is near the bottom of the container and the C 4 H 10 occupies a volume of 0.050 liter. The pressure of the gas versus its volume is plotted in the graph below. The figure shows a graph in a coordinate plane. The horizontal axis is labeled “Volume, in liters,” and the numbers 0.0 through 0.6, in increments of 0.1, are indicated. The vertical axis is labeled “Pressure, in atmospheres,” and the numbers 0.0 through 4.0, in increments of 0.5, are indicated. The graph consists of a line segment and a curve. The line segment begins at the point with coordinates 0.05 comma 2.45 and moves horizontally to the right until it ends at the point with coordinates 0.21 comma 2.45. The curve begins where the line segment ends, and moves downward and to the right. It passes through the points with coordinates 0.3 comma 1.7 and 0.4 comma 1.25, and ends at the point with coordinates 0.5 comma 1.0. Which of the following best explains the increase in pressure of C4H10(g) when its volume is decreased from 0.50 L to 0.21 L?

Benzene, C6H6, has the structure shown below. Considering the observation that benzene is only sparingly soluble in water, which of the following best describes the intermolecular forces of attraction between water and benzene? The Benzene molecule is composed of six carbon atoms joined in a planar ring, with one hydrogen atom single-bonded to each carbon atom. The ring alternates between single and double bonds and has three of each.

Thymine and adenine form a base pair in the DNA molecule. These two bases can form a connection between two strands of DNA via two hydrogen bonds. Which of the following diagrams shows the correct representation of the hydrogen bonding (denoted by dashed lines) between thymine and adenine base pairs? (In each diagram, thymine is shown at the left and adenine is shown at the right. The bases are attached to the backbone portion of the DNA strands.)

Equimolar samples of CH3OH(l) and C2H5OH(l) are placed in separate, previously evacuated, rigid 2.0 L vessels. Each vessel is attached to a pressure gauge, and the temperatures are kept at 300 K. In both vessels, liquid is observed to remain present at the bottom of the container at all times.   Table: Substances, their Lewis Diagrams, and Boiling Points Substance Lewis Diagram Boiling Point CH3OH 338 K C2H5OH 351 K   The change in pressure inside the vessel containing CH3OH(l) is shown in the figure.     Compared to the equilibrium vapor pressure of CH3OH(l) at 300 K, the equilibrium vapor pressure of C2H5OH(l) at 300 K is

Which of the following molecules has an angular (bent) geometry that is commonly represented as a resonance hybrid of two or more electron-dot structures?

The Maxwell-Boltzmann distributions of molecular speeds in samples of two different gases at the same temperature are shown in the figure.

Each student in a class placed a 2.00 g sample of a mixture of Cu and Al in a beaker and placed the beaker in a fume hood. The students slowly poured 15.0 mL of 15.8 M HNO3(aq) into their beakers. The reaction between the copper in the mixture and the HNO3(aq) is represented by the equation below. Cu(s) + 4 HNO3(aq) → Cu(NO3)2(aq) + 2 NO2(g) + 2 H2O(l) The students observed that a brown gas was released from the beakers and that the solutions turned blue, indicating the formation of Cu2+(aq). The solutions were then diluted with distilled water to known volumes. [Cu2+]Absorbance0.0250.0590.0500.2350.1000.1170.2000.468Unknown(from sample of mixture)0.330 To determine the number of moles of Cu in the sample of the mixture, the students measured the absorbance of known concentrations of Cu(NO3)2(aq) using a spectrophotometer. A cuvette filled with some of the solution produced from the sample of the mixture was also tested. The data recorded by one student are shown in the table above. On the basis of the data provided, which of the following is a possible error that the student made?

The volume of distilled water that should be added to 10.0 mL of 6.00 M HCl(aq) in order to prepare a 0.500 M HCl(aq) solution is approximately