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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?

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

The figure shows a particle view of a sample of H 2 O 2 aqueous. There are 10 circles. Each circle is labeled as H 2 O 2. A particle view of a sample of H2O2(aq) is shown above. The H2O2(aq) is titrated with KMnO4(aq), as represented by the equation below.   2 MnO4−(aq) + 5 H2O (aq) + 6 H+(aq) → 2 Mn2+(aq) + 5 O2(g) + 8 H2O(l)   Which of the following particle views best represents the mixture when the titration is halfway to the equivalence point? (H2O molecules and H+ ions are not shown.)

Of the following, the best explanation for the fact that most gases are easily compressed is that the molecules in a gas

N2O, sometimes known as “laughing gas” can be represented with several plausible Lewis Diagrams. Use formal charge to determine which structure, of the three below, is most representative of bonding in the dinitrogen monoxide molecule. Explain, fully, why you have chosen the structure you have. The first structure has an oxygen atom in the center. The nitrogen atoms on either side are connected to the oxygen with double lines. The nitrogen atoms each have a pair of dots on the top and bottom sides of their symbols. The second structure has a nitrogen atom in the center. The nitrogen atom on the left and the oxygen atom on the right are connected to the center atom with double lines. The outside atoms each have a pair of dots on the top and bottom sides of their symbols. Answers must be written in the space provided. Show your work.  Note: 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 provided on scratch paper alone will not be scored. The third structure has a nitrogen atom in the center. The nitrogen atom on the left is connected to the center nitrogen with a single line and the oxygen atom on the right is connected to the center nitrogen with three lines. The outside nitrogen atom has a pair of dots on the top and bottom sides of the symbol and the outside oxygen atom has a pair of dots on its right side.

Determine the molarity of the Cu(NO3)2 found in 100.0 mL of the brass solution using the visual comparison method. Support your answers with the appropriate calculations.

A student uses visible spectrophotometry to determine the concentration of CoCl2(aq) in a sample solution. First the student prepares a set of CoCl2(aq) solutions of known concentration. Then the student uses a spectrophotometer to determine the absorbance of each of the standard solutions at a wavelength of 510 nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration. A wavelength of 510 nm corresponds to an approximate frequency of 6 x 1014 s-1. What is the approximate energy of one photon of this light?

The diagram above shows the distribution of molecular speed in a sample of gas at two different temperatures, T1 and T2. Which of the following is a correct interpretation of the information provided by the diagram? The figure shows a graph of two curves in a coordinate plane. The horizontal axis is labeled “Molecular Speed,” and the vertical axis is labeled “Fraction of Molecules.” The first curve is labeled T sub 1, and begins at the origin. It moves steeply upward and to the right until it reaches a peak at a point near the top of the vertical axis, about one eighth of the way along the horizontal axis. It then moves steeply downward and to the right until it reaches a point just above the horizontal axis, about one fourth of the way along the axis. From here it moves nearly horizontally to the right until it ends far to the right of the vertical axis. The second curve is labeled T sub 2, and begins at the origin. It moves gradually upward and to the right until it reaches a peak at a point about one third of the way up the vertical axis, and about one half of the way along the horizontal axis and to the right of the peak for the curve labeled T sub 1. It then moves gradually downward and to the right and begins to level off as it approaches the horizontal axis. The curve ends just above the horizontal axis, far to the right of the vertical axis.

Ni(s) → Ni2+(aq) + 2e- Ag+(aq) + e- → Ag(s) Which of the following is the balanced net ionic equation for an oxidation-reduction reaction between Ag+(aq) and Ni(s) based on the half-reactions represented above?

2 H2O2(aq) → 2 H2O(l) + O2(g)           ΔH° = −196 kJ/molrxn The decomposition of H2O2(aq) is represented by the equation above. A student monitored the decomposition of a 1.0 L sample of H2O2(aq) at a constant temperature of 300. K and recorded the concentration of H2O2 as a function of time. The results are given in the table below. Time (s)[H2O2]02.7200.2.1400.1.7600.1.4 The O2(g) produced from the decomposition of the 1.0 L sample of H2O2(aq) is collected in a previously evacuated 10.0 L flask at 300. K. What is the approximate pressure in the flask after 400. s? (For estimation purposes, assume that 1.0 mole of gas in 1.0 L exerts a pressure of 24 atm at 300. K.).