2.

Cu(s) + 4 HNO3(aq) → Cu(NO3)2(aq) + 2 NO2(g) + 2 H2O(l)

Each student in a class placed a 2.00 g sample of a mixture of Cu and Al in a beaker and placed the beaker in a fume hood. The students slowly poured 15.0 mL of 15.8 M HNO3(aq) into their beakers. The reaction between the copper in the mixture and the HNO3(aq) is represented by the equation above. The students observed that a brown gas was released from the beakers and that the solutions turned blue, indicating the formation of Cu2+(aq). The solutions were then diluted with distilled water to known volumes.

The students determined that the reaction produced 0.010 mol of Cu(NO3)2 . Based on the measurement, what was the percent of Cu by mass in the original 2.00 g sample of the mixture?

(A) 16%

(B) 32%

(C) 64%

(D) 96%

A B C D

3. Given that the density of Hg(l) at 0°C is about 14 g mL^-1, which of the following is closest to the volume of one mole of Hg(l) at this temperature?

(A) 0.070 mL

(B) 0.14 mL

(C) 1.4 mL

(D) 14 mL

A B C D

4. A student has a 1g sample of each of the following compounds: NaCl, KBr, and KCl. Which of the following lists the samples in order of increasing number of moles in the sample?

(A) NaCl < KCl < KBr

(B) NaCl < KBr < KCl

(C) KCl < NaCl < KBr

(D) KBr < KCl < NaCl

A B C D

5. A student obtains a sample of a pure solid compound. In addition to Avogadro’s number, which of the following must the student know in order to determine how many molecules are in the sample? (A) Mass of the sample, volume of the sample (B) Mass of the sample, density of the sample (C) Molar mass of the compound, mass of the sample (D) Molar mass of the compound, density of the sample

A B C D

6. A solution of methanol, CH₃OH, in water is prepared by mixing together 128g of methanol and 108g of water. The mole fraction of methanol in the solution is closest to
(A) 0.80
(B) 0.60
(C) 0.50
(D) 0.40

A B C D

7. A solution is prepared by adding 16g of CH₃OH (molar mass 32g) to 90.g of H₂O (molar mass 18g). The mole fraction of CH₃OH in this solution is closest to which of the following?
(A) 0.1
(B) 0.2
(C) 0.3
(D) 0.4

A B C D

8. The elements I and Te have similar average atomic masses. A sample that was believed to be a mixture of I and Te was run through a mass spectrometer, resulting in the data above. All of the

(A) Te forms ions with a −2 charge, whereas I forms ions with a −1 charge.

(B) Te is more abundant than I in the universe.

(C) I consists of only one naturally occurring isotope with 74 neutrons, whereas Te has more than one isotope.

(D) I has a higher first ionization energy than Te does.

A B C D

9.In his atomic theory, Dalton proposed that all atoms of a given element are identical. Which of the following observations provides the best evidence that the proposal is incorrect?

(A) The mass spectrum of Cu has a 63 amu peak at and another peak at 65 amu .

(B) The ionic radius of Cl^- is 0.181nm , and the atomic radius of Cl is 0.079nm .

(C) The dipole moment of O₃ is 0.53 debye , and the dipole moment of O₂ is 0.00 debye

(D) Elemental P can exist in both white and red forms.

A B C D