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QUESTION 6 The body uses urea, H2NCONH2, to conduct waste nitrogen from protein decomposition out of...

QUESTION 6

  1. The body uses urea, H2NCONH2, to conduct waste nitrogen from protein decomposition out of the body.Calculate the molar mass of urea and determine the number of moles of nitrogen there are in 12.6 g of urea. The molar masses of the elements are as follows:

    N = 14.01, C = 12.01, O = 16.00, and H = 1.008 (all g/mol)

    a.

    0.42 mol N
    b.

    0.21 mol N
    c.

    0.54 mol N
    d.

    0.47 mol N
    e.

    None of the above

QUESTION 7

  1. The volume of a balloon is 404 L at earth’s surface and T = 23.0 °C. The sun warms the balloon to 41.7 °C. What is the new volume of the balloon? This is a Charles’ law problem, V = kT.

    TK = TC  + 273

    a.

    263 L
    b.

    380 L
    c.

    430 L
    d.

    732 L
    e.

    None of the above

QUESTION 8

  1. Molarity is the moles of solute (dissolved substance) in a liter of solution. The formula for molarity is M = n/V and the units are moles per liter. What is the molarity of a salt solution if 88.0 grams of sodium chloride are dissolved in enough water to make a volume of 550.0 mL? The molar mass of sodium chloride is 58.44 g/mol.

    a.

    1.60 M
    b.

    2.74 M
    c.

    6.25 M
    d.

    3.65 M
    e.

    None of the above

QUESTION 9

  1. A student needs to make a less concentrated solution of hydrochloric acid from an original   solution that is 6.0 M HCl. How many milliliters of the original solution will she need to make 300.0 mL of a 0.25 M solution? You may use the dilution equation:

    Voriginal x   Coriginal ----> Vfinal x Cfinal

    a.

    7.2 mL
    b.

    4.5 mL
    c.

    8.0 mL
    d.

    12.5 mL
    e.

    None of the above

Question 10

According to Boyle’s law (PV = k), when the pressure on a gas is doubled (at constant temperature), its volume will:

a.

Remain the same
b.

Quadruple
c.

Double
d.

Be reduced to 1/2
e.

None of the above

QUESTION 11

  1. How many grams of AgNO3 are required to make 770.0 mL of a 0.15 M solution?

    The molar mass of silver nitrate is 169.9 g/mol. One approach is to solve the molarity relationship (M = n/V) for moles.

    a.

    19.6 g
    b.

    6.82 g
    c.

    5.10 g
    d.

    1.95 g
    e.

    None of the above

QUESTION 12

  1. Which of the following solutions is a buffer?

    a.

    A solution with a large concentration of a weak acid
    b.

    A solution with equal amounts of a weak acid and its conjugate base
    c.

    A solution with pH five times larger than pKa
    d.

    A solution with equal amounts of HNO3 and NH3
    e.

    None of the above

QUESTION 13

  1. An equilibrium mixture of carbonic acid (H2CO3) and bicarbonate (HCO3–) has

    pH = pKa = 6.6. What will happen to the carbonic acid and bicarbonate concentrations if the pH is raised to 8.2?

    a.

    Both concentrations will increase
    b.

    The concentration of H2CO3 will increase and the concentration of HCO3– will decrease
    c.

    pKa will increase by 1.6 units
    d.

    The concentration of H2CO3 will decrease and the concentration of HCO3– will increase
    e.

    None of the above

QUESTION 14

  1. Which of the following is a good description of a base?

    a.

    A compound that can react with an acid
    b.

    A compound that can add H+ in a neutralization reaction
    c.

    A compound that has a lone pair like ammonia, NH3
    d.

    A compound that can increase the concentration of hydroxide, OH–, in a solution
    e.

    All of the above

QUESTION 15

  1. What is the OH– concentration of a solution in which the hydronium ion concentration is 5.4 x 10-8 M?

    Kw = [H+][OH-] = 1.0 x 10-14

    a.

    5.40 x 10-6 M
    b.

    1.85 x 10-7 M
    c.

    5.40 x 10-14 M
    d.

    7.20 x 10-7 M
    e.

    None of the above

QUESTION 16

  1. A 30.0 mL sample of HCl was titrated to a pink endpoint with 25.8 mL of 0.200 MNaOH. Calculate the concentration of the HCl solution.

    a.

    0.232 M
    b.

    0.155 M
    c.

    0.172 M
    d.

    0.581 M
    e.

    None of the above

QUESTION 17

  1. When the methylammonium ion (CH3NH3+) comes into contact with a strong base like sodium hydroxide, which of the following is most likely to happen?

    a.

    It will decompose to methane and ammonia
    b.

    It will react strongly with the sodium ion, Na+
    c.

    It will lose an H+ to the hydroxide and a water molecule will be formed
    d.

    It will become its conjugate base, (CH3NH2)
    e.

    Both (c) and (d) are true

QUESTION 18

  1. A sample of stomach fluid is found to contain, on average, 0.0322 mol of H+ for every 0.450 L of solution. Calculate the concentration of H+ and then the pH of this fluid. pH = -log[H+]

    a.

    pH = 3.13
    b.

    pH = 1.84
    c.

    pH = 1.15
    d.

    pH = 0.873
    e.

    None of the above

QUESTION 19

  1. A weak vinegar solution was found to have a pH of 6.44. What is the concentration of H+ in this vinegar?    [H+] = 10-pH

    a.

    2.75 x 10-7 M
    b.

    3.63 x 10-7 M
    c.

    6.44 x 10-6 M
    d.

    8.90 x 10-6 M

QUESTION 20

  1. Which of the following is an important measure of solution concentration?

    a.

    Moles
    b.

    Milliliters
    c.

    Molarity
    d.

    Mass
    e.

    (b) and (c) are correct
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