According to the VSEPR model, the progressive decrease in the bond angles in the series of molecules CH4, NH3, and H2O is best accounted for by the

When 0.20 M NH4Cl(aq) and 0.20 M NaOH(aq) are mixed, the reaction represented by the equation below occurs and a strong smell of ammonia, NH3, is observed. NH₄⁺(aq) + OH⁻(aq) → NH₃(aq) + H₂O(l) Based on this information, which of the following statements is true?

Investigate the following compounds. Identify the color of the crystal and the resulting solution made from the compound.  Compound Name Color of Solid Color of Solution zinc nitrate copper (II) nitrate zinc sulfate copper (II) sulfate iron (III) nitrate iron (III) sulfate

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?

Which of the following best explains why more energy is required for the process occurring at 110 K than for the process occurring at 90 K?

Which of the following particulate diagrams best shows the formation of water vapor from hydrogen gas and oxygen gas in a rigid container at 125oC?

If equal masses of the following compounds undergo complete combustion, which will yield the greatest mass of CO2?

A student is helping clean up the chemical supply closet where humidity has caused the labels to fall off some of their containers. The supply closet contains two unknown canisters of gas. One is compressed helium, and one is compressed nitrogen, but without the labels it is unclear which is which. The student uses gas collection over water to determine the molar mass of the gas. Initial Mass of Gas Canister 93.230 Final Mass of Gas Canister 93.129 Mass of Gas Expelled from the Canister 0.101 Volume of Gas Collected 88.5 mL Water Temperature 22℃ Vapor Pressure of Water at 22℃ 0.0260 atm Atmospheric Pressure 1.013 atm   Use the data in the table to determine the moles of the gas expelled from the canister. Use the data in the table to determine the molar mass of the unknown gas. Based on the data, is the unknown gas nitrogen or helium? If the student had failed to consider the vapor pressure of the water to find the corrected pressure of the gas, and instead used the atmospheric pressure, would the calculated value for the molar mass of the unknown gas be larger or smaller than the actual value? Explain. Gas collection over water works in this situation because both nitrogen and helium are mostly insoluble in water. If the unknown gas were very soluble, would the calculated value for the molar mass of the unknown gas be larger or smaller than the actual value? Explain. Show your work for all calculations. 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.

Which of the following substances has the greatest solubility in C5H12(l) at 1 atm?

The reaction represented below goes essentially to completion. The reaction takes place in a rigid, insulated vessel that is initially at 600 K   CH3OH(g) → CO(g) + 2 H2(g) ΔH° = +91 kJ/molrxn   A sample of CH3OH(g) is placed in the previously evacuated vessel with a pressure of P1 at 600 K. What is the final pressure in the vessel after the reaction is complete and the contents of the vessel are returned to 600 K?