An experiment was performed to investigate the reaction between Zn metal and Ni2+ (aq)at different concentrations. Because the Ni2+ (aq)ion is green, the extent of the reaction was determined using spectrophotometric analysis. Four 20.0 mL standard solutions of Ni2+ (aq) were prepared by dissolving NiCl2 ⦁ 6H20 (molar mass 240 g/mol)) in water. The absorbance of each solution was measured; the results are shown both in the table below and in the following plot of the absorbance data.   Solution [Ni2+] Absorbance 1 0.020 0.12 2 0.040 0.25 3 0.060 0.39 4 0.080 0.51 The figure shows a graph of four data points in a coordinate plane. The horizontal axis is labeled “Concentration, in moles per liter,” and the numbers 0 through 0.10, in increments of 0.020, are indicated. The vertical axis is labeled “Absorbance,” and the numbers 0 through 0.6, in increments of 0.1, are indicated. The coordinates of each data point are as follows. Note that all values are approximate. Data point 1: 0.020 comma 0.12. Data point 2: 0.040 comma 0.27. Data point 3: 0.061 comma 0.39. Data point 4: 0.082 comma 0.51. What is the expected absorbance of a standard solution made by dissolving 0.0070 mol of NiCl2 ⦁ 6H20 in water to make 100. mL of solution?

The diagram below represents the photoelectric effect for a metal. When the metal surface is exposed to light with increasing frequency and energy of photons, electrons first begin to be ejected from the metal when the energy of the photons is 3.3 ✕ 10-19 J. The figure presents a box with several electrons represented by circles with a negative sign on the inside of each. Outside the upper left-hand side of the box of electrons there are two wavy arrows pointing at an angle towards the box. Inside the center of the box of electrons, there is one arrow pointing from an electron at an angle out of the box. Outside the upper right-hand side of the box of electrons there are two more electrons each with an arrow pointing from the electron at an angle away from the box. Which of the following is closest to the frequency of the light with photon energy of 3.3 ✕ 10-19 J?

The graph shows the distribution of molecular speeds for four different gases at the same temperature. What property of the different gases can be correctly ranked using information from the graph, and why? The figure presents a graph of 4 curves with horizontal axis labeled Molecular Speed, in meters per second, and vertical axis labeled Number of Molecules. The first curve is a bolded line that begins near the origin and moves drastically upward and to the right, reaching its peak roughly 10% across the horizontal axis and 95% up the vertical axis, then moves drastically downward and to the right, reaching the lowest point at roughly 25% across the horizontal access, after which it moves horizontally to the right until reaching the rightmost point on the vertical axis. The second curve is a nonbolded line that begins near the origin and moves very steeply upward and to the right, reaching its peak roughly 20% across the horizontal axis and 50% up the vertical axis, then moves very steeply downward and to the right, reaching the lowest point at roughly 30% across the horizontal access, after which it moves horizontally to the right until reaching the rightmost point on the vertical axis. The third curve is a dashed line that begins at the origin and moves steeply upward and to the right, reaching its peak roughly 30% across the horizontal axis and 30% up the vertical axis, then moves steeply downward and to the right, reaching the lowest point approximately 50% across the vertical axis and moving horizontally until reaching the rightmost point on the horizontal axis. The fourth curve is a dotted line that begins near the origin and gradually moves upward and to the right, reaching its maximum point halfway across the horizontal axis and roughly 25% up the vertical axis, before gradually moving downward and to the right, ending at the rightmost part of the horizontal axis and at the lowest point on the vertical axis.

A sample of a compound that contains only the elements C, H, and N is completely burned in O2 to produce 44.0 g of CO2, 45.0 g of H2O, and some NO2 . A possible empirical formula of the compound is

The reaction in which a single species is both oxidized and reduced:

The diagram represents a particle in aqueous solution. Which of the following statements about the particle is correct?   The figure presents a particle diagram. A particle represented by a large circle is shown at the center of the diagram. There are four water molecules surrounding it. Each water molecule is represented by one medium sized circle, with two smaller circles attached to it. The smaller circles in the water molecule are pointed toward the large circle at the center of the diagram.

M+ is an unknown metal cation with a +1 charge. A student dissolves the chloride of the unknown metal, MCl, in enough water to make 100.0 mL of solution. The student then mixes the solution with excess AgNO3 solution, causing AgCl to precipitate. The student collects the precipitate by filtration, dries it, and records the data shown below. (The molar mass of AgCl is 143 g/mol.)   Mass of unknown chloride, MCl 0.74 g Mass of filter paper 0.80 g Mass of filter paper plus AgCl precipitate 2.23 g     What is the identity of the metal chloride?

A 360. mg sample of aspirin, C9H8O4, (molar mass 180. g), is dissolved in enough water to produce 200. mL of solution. What is the molarity of aspirin in a 50. mL sample of this solution?

2 Al(s) + 6 HCl(aq) → 2 AlCl3(aq) + 3 H2(g) According to the reaction represented above, about how many grams of aluminum (atomic mass 27 g) are necessary to produce 0.50 mol of hydrogen gas at 25ºC and 1.00 atm?

A 50 mL sample of C6H14(l) is mixed with a 50 mL sample of H20(l), and the mixture is shaken vigorously. The two liquids do not stay mixed but instead form two separate layers. The density of hexane is 0.66 g/mL, and the density of water is 1.00 g/mL. A 1.0 g sample of I2 (s) is added to the mixture, which is shaken again. Which of the following best predicts what happens to the I2 (s)? The figure shows a three column table with four rows of data. The heading for column 1 is “Compound.” The heading for column 2 is “Structure.” The heading for column 3 is “Boiling Point, in degrees Celsius.” The data in the table are as follows. Row 1. Compound: Methanol. Structure: A C atom is connected to 3 H atoms and 1 O atom, each by a single bond. The O atom has two pairs of nonbonding electrons. The O atom is connected to an H atom by a single bond. Boiling Point: 65 degrees Celsius. Row 2. Compound: Ethanol. Structure: 1 C atom is connected to 3 H atoms and 1 C atom, each by a single bond. The second C atom is connected to 2 H atoms and 1 O atom, each by a single bond. The O atom has two pairs of nonbonding electrons. The O atom is connected to 1 H atom by a single bond. Boiling Point: 78 degrees Celsius. Row 3. Compound: Propanal. Structure: 1 C atom is connected to 3 H atoms and 1 C atom, each by a single bond. The second C atom is connected to 2 H atoms and 1 additional C atom, each by a single bond. The C atom is connected to 1 O atom by a double bond and 1 H atom by a single bond. The O atom has two pairs of nonbonding electrons. Boiling Point: 49 degrees Celsius. Row 4. Compound: Hexane. Structure: 6 C atoms are arranged in a horizontal row, each connected by a single bond. The leftmost and rightmost C atoms are each connected to 3 H atoms by single bonds. The middle 4 C atoms are each connected to 2 H atoms by single bonds. Boiling Point: 69 degrees Celsius.