The distribution of speeds of H2(g) molecules at 273 K and 1 atm is shown in the diagram.   The figure shows a graph with the horizontal axis labeled Speed and the vertical axis labeled Fraction of Particles. A solid line starts at the origin, curves up to a height about one-third of the vertical axis at about the middle of the horizontal axis, then curves down again to end very close to the horizontal axis at the right side of the graph.   Which of the following best shows the speed distribution of He(g) atoms under the same conditions of temperature and pressure?   Two lines: a solid line representing H 2 gas and a dashed line representing H e gas.

Solid Al (NO3)3 is added to distilled water to produce a solution in which the concentration of nitrate, [NO3-] 0.10 M. What is the concentration of aluminum ion, [Al3+], in this solution?

Cu(s) + 2 AgNO₃(aq) → Cu(NO₃)₂(aq) + 2 Ag(s)   The reaction between solid copper and aqueous silver nitrate produces solid silver and a blue solution, as represented by the balanced equation shown above. Based on the balanced equation, which of the following identifies the oxidation and reduction half-reactions?

Determine the mass of Cu dissolved in the brass solution based upon the molarities from both methods.

3 Ag(s) + 4 HNO3 → 3 AgNO3 + NO(g) + 2 H2O The reaction of silver metal and dilute nitric acid proceeds according to the equation above. If 0.10 mole of powdered silver is added to 10. milliliters of 6.0–molar nitric acid, the number of moles of NO gas that can be formed is

Suppose that a stable element with atomic number 119, named matherium, has been discovered. The mass spectrum of a pure sample of matherium is shown below. The horizontal axis is labeled Mass (AMU) with four marked intervals numbered in increments of five starting from 285. The vertical axis is labeled percentage abundance with five marked intervals numbered in increments of 25 starting from zero. Three blue bars appear on the graph. The first bar indicates a mass of 294 AMU and a percentage abundance of 31. The second bar indicates a mass of 297 AMU and a percentage abundance of 58. The third bar indicates a mass of 301 AMU with a percentage abundance of 11. How many protons and how many neutrons are in the nucleus of an atom of the most abundant isotope of matherium? Write the ground-state electron configuration of matherium, showing only the valence-shell electrons. Use the mass spectrum to determine the atomic mass that will be reported on the Periodic Table for matherium. Using principles of atomic structure, explain why the matherium has a fairly low first ionization energy, but a relatively high second ionization energy. Below are two photoelectron spectra. Which one represents an element that is in the same family as element matherium? Justify your answer.   The horizontal axis is labeled “binding energy per mole electron (MJ)” and has five decreasing intervals numbered 1000, 100, 10, 1, and 0.1. The vertical axis is labeled “number of electrons” and has increasing intervals numbered 1 through 6. There are four peaks on the graph. The first peak is occurs just below 100 MJ and has a height indicating two electrons. The second peak occurs right around 10 MJ and has a height indicating two electrons. The third peak occurs immediately to the right of the second peak and has a height indicating 6 electrons. The fourth peak occurs just after 1 MJ and has a height indicating 2 electrons. The horizontal axis is labeled “binding energy per mole electron (MJ)” and has five decreasing intervals numbered 1000, 100, 10, 1, and 0.1. The vertical axis is labeled “number of electrons” and has increasing intervals numbered 1 through 6. There are four peaks on the graph. The first peak is occurs right around 100 MJ and has a height indicating two electrons. The second peak occurs just above10 MJ and has a height indicating two electrons. The third peak occurs immediately to the right of the second peak and has a height indicating 6 electrons. The fourth peak occurs after 1 MJ and has a height indicating 1 electron.

Fe3+(aq) + KSCN(s) → FeSCN2+(aq) + K+(aq)   To determine the moles of Fe3+(aq) in a 100. mL sample of an unknown solution, excess KSCN(s) is added to convert all the Fe3+(aq) into the dark red species FeSCN2+(aq), as represented by the equation above. The absorbance of FeSCN2+(aq) at different concentrations is shown in the graph below.   The figure presents the graph in the first quadrant of a coordinate plane. The horizontal axis is labeled “Concentration of F e S C N with a positive 2 charge, in Molar,” and the following three numbers are indicated: 0, 5 times 10 to the negative 5, and 10 times 10 to the negative 5, in increments of 1 times 10 to the negative 5. The vertical axis is labeled “Absorbance at 453 nanometers,” and the numbers 0 through 0 points 5 0, in increments of 0 point 1 0, are indicated. The line of best fit is drawn. The line begins where the axes meet. It moves steadily upward and to the right passing through the point 5 times 10 to the negative 5 Molar and 0 point 2 5 absorbance. The line ends at 10 times 10 to the negative 5 Molar and 0 point 5 0 absorbance. There are 6 data points along the line. 1 point is at the origin, 3 points are above the line, and 2 points are below. If the absorbance of the mixture is 0.20 at 453 nm, how many moles of Fe3+(aq) were present in the 100. mL sample? (Assume that any volume change due to adding the KSCN(s) is negligible.)

A student is analyzing an unknown compound made only of carbon, hydrogen, and oxygen. She burns 1.246 g of the unknown and recovers 1.823g of CO2. She also recovers and analyzes the resulting water from the combustion.  Determine the mass, in grams, of carbon in the 1.246 g sample of the compound. Her analysis of the water vapor reveals that hydrogen is 6.727% of the total compound. Determine the mass, in grams of hydrogen in the original 1.246 g sample.  Determine the empirical formula of the unknown compound. Using a mass spectrometer, the molecular mass is determined to be 180. g/mol. What is the molecular formula of the unknown compound?  Show your work. Note: Your answer(s) must be provided in this text box. If you are unable to show your work adequately using the Rich Text Editor, complete your work on scratch paper. Upload a photo of your work in the “Comments” of this exam immediately after you have completed and submitted the exam. You can access the “Comments” through the grade book. Answers on scratch paper alone will not be scored.

An experiment is performed to measure the mass percent of CaCO3(s) in eggshells. Five different samples of CaCO3(s) of known mass react with an excess of 2.0 M HCl(aq) in identical sealed, rigid reaction vessels. The pressure of the gas produced is measured with a pressure gauge attached to the reaction vessel. Since the reaction is exothermic, the reaction system is cooled to its original temperature before the pressure is recorded. The experimental data are used to create the calibrated line in the chart. The figure presents a graph consisting of five points and a straight line of best fit. The horizontal axis is labeled “Mass of C a C O 3, solid, in grams,” and the numbers 0.05 through 0.20, in increments of 0.05, are indicated. The vertical axis is labeled “Pressure of Gas Produced, in atmospheres,” and the numbers 0.02 through 0.10, in increments of 0.01, are indicated. The data represented in the graph are as follows. Note that all values are approximate. The line begins at a mass of 0.06 gram and a pressure of 0.03 atmosphere, and ends at a mass of 0.21 gram and a pressure of 0.10 atmosphere. The data points are at 0.07 gram and 0.032 atmosphere; 0.09 gram and 0.045 atmosphere; 0.14 gram and 0.068 atmosphere; 0.17 gram and 0.08 atmosphere; and 0.20 gram and 0.096 atmosphere. The experiment is repeated with an eggshell sample, and the experimental data are recorded in the table. Mass of eggshell sample 0.200 g Pressure prior to reaction 0.800 atm Pressure at completion of reaction 0.870 atm   Which of the following equations best represents the species that react and the species that are produced when CaCO3(s) and HCl(aq) are combined?

The figure presents C H 4 and O 2 gas molecules in a vessel. There is a key that shows that a small unshaded circle represents H, a larger dark shaded circle represents C, and a lightly shaded circle represents O. In the mixture there are 2 C H 4 molecules and 6 O 2 molecules. The reactants represented above are placed in a vessel and a reaction occurs. Which of the following best represents the contents of the vessel after the reaction has proceeded as completely as possible?