ACS exam practice Questions and Answers

ACS exam practice Questions and Answers Copper electrodes are placed into two aqueous solutions of copper(II) sulfate at 25 ºC. One compartment contains a 1.0 M solution while the other compartment contains a 0.10 M solution. The two compartments are connected with a salt bridge and the e lectrodes are connected by a wire passing through a voltmeter. In what direction do the electrons flow through the wire, and what is the cell potential read on the voltmeter? Direction of electron flow Cell potential (A)Direction of electron flow: From the electrode in the 1.0 M solution to the electrode in the 0.10 M solution Cell potential: 30 mV (B)Direction of electron flow: From the electrode in the 1.0 M solution to the electrode in the 0.10 M solution Cell potential: 59 mV (C)Direction of electro n flow: From the electrode in the 0.10 M solution to the electrode in the 1.0 M solution Cell potential: 30 mV (D)Direction of electron flow: From the electrode in the Ans- Direction of electron flow: From the electrode in the 0.10 M solution to the electrode in the 1.0 M solution Cell potential: 30 mV How many oxygen atoms are in 225 g O2? Ans- 8.47x10^24 A 0.300 M solution of HCl is prepared by adding some 1.50 M HCl t o a 500 mL volumetric flask and diluting to the mark with deionized water. What volume of 1.50 M HCl must be added? Ans- 100 mL Copper(I) oxide, Cu2O, is reduced to metallic copper by heating in a stream of hydrogen gas. What mass of water is produced w hen 10.00 g copper is formed? Ans- 1.417 g The mineral enargite is 48.41% Cu, 19.02% As, and 32.57% S by mass. What is the empirical formula of enargite?Cu3AsS4 Ans- Cu3AsS4 A 5.0 g sample of calcium nitrate (Ca(NO3)2, M = 164) contaminated with sili ca (SiO2, M = 60.1) is found to contain 1.0 g calcium. What is the mass percent purity of calcium nitrate in the sample? Ans- 82% A solution of 20.0 g of which hydrated salt dissolved in 200 g H2O will have the lowest freezing point? Ans- The one with the highest molarity Addition of 6 M HCl to which substance will NOT result in gas evolution?