Author: Anonymous

If 200. mL of 0.60 M MgCl2(aq) is added to 400. mL of distilled water, what is the concentration of Mg2+(aq) in the resulting solution? (Assume volumes are additive).

Which of the following describes the changes in forces of attraction that occur as H2O changes phase from a liquid to a vapor?

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.)

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.

N2 molecules absorb ultraviolet light but not visible light. I2 molecules absorb both visible and ultraviolet light. Which of the following statements explains the observations?

When a student adds 30.0 mL of 1.00 M HC1 to 0.56 g of powdered Fe, a reaction occurs according to the equation below. When the reaction is complete at 273 K and 1.0 atm, which of the following is true?   Fe(s) + 2 HCl(aq) → FeCl2(aq) + H2(g)

An experiment is performed to measure the mass percent of CaCO3(s) in eggshells. Five different samples of CaCO3(s) known mass react with an excess of 2.0 M HC1(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 calibration line below. 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 below.   Table: Experimental Data Mass of eggshell example 0.200 g Pressure prior to reaction 0.800 atm Pressure at completion of reaction 0.870 atm   Another sample of eggshell reacts completely with 4.0 mL of an HC1(aq) solution of unknown concentration. If the reaction produced 0.095 atm of gas, the concentration of the HC1(aq) solution was at least

A sample of an ideal gas is cooled from 50.0°C to 25.0°C in a sealed container of constant volume. Which of the following values for the gas will decrease? I. The average molecular mass of the gasII. The average distance between the moleculesIII. The average speed of the molecules

An unknown element combines with fluorine to form the compound XF3. Assume all atoms follow the octet rule. Draw the most plausible Lewis Structure and answer the following questions.  What is the geometry around the central, unknown atom?  Predict approximate bond angles in this molecule. Using a mass spectrometer, the molecular mass of the compound is determined to be 88. g/mol. What is the identity of the unknown element?  Predict the formula of the ionic compound formed when element X bonds with magnesium (Mg). Explain your answer. 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.

Solid ethyl alcohol, C2H5OH