CH 201 Fall 2004

Exam 1 Key

1. Which of the following statements about the element calcium is correct?

            a) Calcium is a metal that forms a 2+ cation. Its symbol is Ca.

            b) Calcium is a non-metal that forms a 4+ cation. Its symbol is C.

            c) Calcium is a non-metal that forms a 2- anion. Its symbol is Cl.

            d) Calcium is a metal that forms a 4-  anion. Its symbol is C.

2.  Which one of the following statements about non-metals is incorrect?

            a) Non-metals gain electrons to form anions.

            b) Non-metals combine using covalent bonds to form molecules.

            c) Non-metal ions combine with cations to form ionic compounds.

            d) Non-metals are located in groups 10-18 of the periodic table.

3.  What is the correct formula of manganese(III) oxide?

            a) MgO

            b) Mg₂O

            c) Mg₃O

            d) Mn₃O

            e) Mn₂O₃

4.  What is the correct name for K₂SO₄?

            a) calcium sulfide

            b) chromium (II) sulfide

            c) chromium sulfate

            d) potassium sulfoxide

            e) potassium sulfate

5.  Nitrous oxide (laughing gas) is the common name for dinitrogen oxide, an anesthetic used in dentistry. What is the formula of nitrous oxide?

            a) NO₂

            b) NO₃^-

            c) N₂O

            d) N₂O₄

            e) NH₃

6. Which of the following statements about atomic structure is incorrect?

            a) Protons and neutrons are located within the nucleus of an atom.

            b) The nucleus is positively charged.

            c) For a single element, the number of protons can vary to give isotopes.

            d) For a single element, the number of electrons can vary to give ions.

            e) As atomic numbers in the periodic table increase, the number of protons in     each element increases.

7. The symbol ⁹⁰Y ³⁺ represents an atom with

            a) 90 protons, 39 neutrons, and 93 electrons    

            b) 39 protons, 51 neutrons, and 54 electrons

            c) 51 protons, 39 neutrons, and 54 electrons

            d) 51 protons, 39 neutrons, and 48 electrons

            e) 39 protons, 51 neutrons, and 36 electrons

8.  Copper has two naturally occurring isotopes. Cu-63 has an atomic mass of 62.9296 amu and an abundance of 69.17%.  What is the atomic mass of the second isotope?

            a) 63.546 amu

            b) 43.528 amu

            c) 64.930 amu

            d) 65.782 amu

9.  Which of the following compounds is 17.8 % hydrogen by mass?

            a) sodium hydroxide

            b) ammonia

            c) carbon dioxide

            d) calcium nitrate

10.  A compound is analyzed and found to contain 26.56% potassium, 35.36% chromium, and 38.08% oxygen. What is the empirical formula of this compound?

            a) KMnO₄

            b) K₂Cr₂O₇

            c) KCr₂O₄

            d) KClO₄

11.  The density of water is 1.00 g/mL. How many moles of water are present in 4.62 L?

            a) 83.2 moles

            b) 257 moles

            c) 4.62 moles

            d) 3.90 moles

12.  There are 4.20 x 10²¹ valium molecules in 2.00 g of valium.  What is the molar mass of valium?

      a) 392 g/mol

      b) 287 g/mol

      c) 840 g/mol

      d) The answer cannot be calculated without the molecular formula of valium.

13. The unbalanced reaction for the combustion of methane is shown below.  If  7 moles of methane are combined with 12 moles of oxygen, how many moles of carbon dioxide are expected to form?

CH₄(g)   +     O₂(g)   à     CO₂(g)   +      H₂O(g)

      a) 7 moles of CO₂

      b) 6 moles of CO₂

      c) 12 moles of CO₂

      d) 14 moles of CO₂

14. Which of the following aqueous solutions has the highest concentration of ammonium ion?

      a) 0.40 M NH₄OH

      b) 0.20M (NH₄)₂SO₄

      c) 0.25 M (NH₄)₃PO₄

      d) 0.30 M (NH₄)₂CO₃

15. When sulfuric acid and barium hydroxide are combined, an acid base reaction occurs, and a precipitate forms. What is the formula of the precipitate?

H₂SO₄ (aq)  + Ba(OH)₂ (aq)  à        ?????

a) H₂O

b) Ba(OH)₂

c) (OH)₂SO₄

d) BaSO₄

e) BaH₂

16.  Which is the strongest electrolyte when dissolved in water?

a)      an ice cube

b)      ammonia

c)      sucrose (C₁₂H₂₂O₁₁)

d)      hydrobromic acid

e)      acetic acid

17)  93.2 g of sodium chloride are dissolved in water and brought to a total volume of  525 mL. What is the molarity of this solution?

            a) 0.178 M

            b) 5.63 M

            c) 3.03 M

            d) 1.26 M

18) Consider the following reaction and choose the one incorrect statement from the choices below:

                        2  HNO₃ (aq)  +   Ca(OH)₂ (aq)  à    Ca(NO₃)₂  (aq) +     2  H₂O

            a) This is the reaction of a strong acid and a strong base.

            b) Calcium and nitrate are spectator ions in this reaction.

            c) No precipitate forms in this reaction.

            d) The conjugate base of nitric acid is the nitrate ion.

            e) The water molecules formed in the reaction are completely ionized.

19)  Provide the coefficients needed to balance the following equation:

a   Na₃PO₄    +   b  ZnCl₂   à    c  Zn₃(PO₄)₂         +   d  NaCl

a)      a=1, b=2, c=2, d=3

b)      a=3, b=3, c=1, d=6

c)      a=2, b=3, c=2, d=3

d)      a=2, b=3, c=1, d=6

e)      a=3, b=2, c=2, d=3

20) A 23.41 mL solution of hydrochloric acid is titrated with 0.1131M sodium hydroxide. It takes 34.33 mL of the sodium hydroxide to reach the equivalence point. What was the concentration of the hydrochloric acid?

            a) 0.1659 M

            b) 0.07710 M

            c) 0.6028 M

            d) 0.1299 M