Download WATER TAKS QUESTIONS

WATER AND SOLUTIONS EXAM – January 2012
PLEASE DO NOT WRITE ON THIS EXAM – USE YOUR ANSWER DOCUMENT TO
RECORD THE CORRECT RESPONSES
(1) What characteristic of water remains the same no matter what is dissolved in it?
A The ratio of hydrogen to oxygen
B The ability to refract light
C The hydroxide ion concentration
D The freezing temperature
(2) Which factor makes water an effective solvent?
A The presence of molecular oxygen
B Its lack of covalent bonds
C The polar nature of its molecules
D Its abundance on Earth’s surface
(3) Fish survive through severe winters because of the property of water that allows water to —
A form chemical bonds as it freezes, raising the water temperature below the ice
B increase in density while it freezes, dissolving more oxygen from the air
C expand when it freezes, creating a floating and insulating layer of ice
D precipitate vital nutrients when it freezes, increasing the food supply
(4) The diagram above shows water molecules and ions from a NaCl crystal. What is the most
likely reason that each water molecule is arranged so that the oxygen part of the molecule faces a
sodium ion?
A The oxygen in a water molecule contains a partial negative charge.
B Gravity rotates the oxygen atoms to face the more-massive sodium ions.
C Hydrogen atoms create repulsive forces with chloride ions.
D Oxygen atoms form covalent bonds with sodium ions.
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(5) Water acts as a solvent of ionic compounds because —
A water is liquid over a wide range of temperatures
B water molecules are polar
C water is found in three states of matter
D water takes the shape of its container
(6) The graph shows the concentration of ions found in the water of the Dead Sea. Which property
of water is responsible for the dissociation of salts that produces the ion concentrations shown in the
graph?
A Chemical stability
B High polarity
C Low melting point
D High freezing point
(7) Which characteristic of water best explains its ability to dissolve a great variety of materials?
A Its transparency in light
B Its electrical conductivity
C Its physical state of matter
D Its molecular arrangement
(8) Which of the following salts has the greatest solubility in water at 25°C?
A CaCO3
B FeS
C HgCl2
D KClO4
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(9) A 0.2 g crystal of gypsum dissolves very slowly in 100 mL of water while the water is stirred.
Which of these would cause the gypsum to dissolve faster?
A Decreasing the water temperature
B Stopping the stirring
C Lowering the air pressure
D Crushing the crystal
(10) All of these can affect the rate at which a solid dissolves in water except —
A decreasing air pressure
B stirring the water
C increasing the temperature of the water
D using larger crystals of the solid
(11) Over time an open soft drink will lose carbonation (dissolved CO2). Which of these allows the
CO2 to remain in solution the longest?
A Reduced air pressure
B Exposure to direct sunlight
C Increased air currents
D Cooler temperatures
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(12)
Nine groups of students dissolved as much potassium chloride as possible in water. Each group
used 100 mL of water heated to a different temperature. Which graph shows the relationship
between solubility and temperature for potassium chloride?
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(13) Power plants that discharge warm water into rivers have a negative effect on aquatic life. This
is because the higher water temperature —
A increases the pressure of the river water
B increases the pH value of the river water
C decreases sediment solubility in the river water
D decreases the dissolved oxygen in the river water
(14) A recipe calls for 210 grams of sugar to be dissolved in 0.25 liter of water. After the mixture is
stirred, some sugar crystals remain in the water. What can be added to the mixture to help dissolve
the remaining sugar crystals?
A Thermal energy
B 2.0 g of baking soda
C Ice cubes
D 2.0 g of sodium chloride
(15) Which of the following describes a trend in the data shown in the graph above?
A The solubility of all the salts increases as temperature increases.
B As temperature increases from 30°C to 60°C, the solubility of KNO3 increases more than
that of KCl.
C An increase in atmospheric pressure causes an increase in the solubility of KCl.
D Increasing the temperature of a KNO3 solution from 30°C to 60°C decreases the solubility
of KNO3 by half.
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Answer questions 16 – 18 after reading the following passage:
ScienceDaily (July 27, 2011) — Scientists are reporting development of a new aquatic microrobot
that mimics the amazing water-walking abilities of the water strider -- the long-legged insect that
scoots across the surface of ponds, lakes and other waterways. The bionic microrobot incorporates
improvements over previous devices of this kind that position it as a prime candidate for military
spy missions, water pollution monitoring, and other applications, the scientists say.
The scientists describe progress on a new robot, with a body about the size of a quarter; ten waterrepellent, wire legs; and two movable, oar-like legs -- propelled by two miniature motors. "Because
the weight of the microrobot is equal to that of about 390 water striders, one might expect that it
will sink quickly when placed on the water surface," the report noted. However, it stands
effortlessly on water surfaces and also walks and turns freely.
(16) The author describes two legs of the robot to be water-repellent. This indicates that the legs
are:
A Are made up of non-polar chemicals
B Made up of polar chemicals
C Can move extremely fast
D Don’t have very much mass
(17) The water strider is able to scoot across the surface of ponds because of water’s:
A Ability to dissolve chemicals
B Resistance to temperature change
C Surface tension
D Thickness in pond areas
(18) If the researchers wanted to see the microrobot’s ability to stay on water’s surface with the
motion of waves of ocean water.
A The amount of marine life will increase its ability to stay afloat.
B Increasing of the speed of wave motion will decrease the time it will float.
C The salt of the ocean water will cause the legs to loose its ability to float.
D The more its mass the less likely it will stay on water’s surface.
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Read the following passage to answer questions 19 – 20:
ScienceDaily (Jan. 26, 2011) — In the report, Yuri M. Lvov and colleagues point out that many
drugs, including some of the most powerful anti-cancer medications, have low solubility in water.
IV administration of large amounts can lead to clumping that blocks small blood vessels, so doses
sometimes must be kept below the most effective level. In addition, drug companies may
discontinue work on very promising potential new drugs that have low solubility. The scientists
note numerous efforts to improve the solubility of such medications, none of which have been ideal.
The scientists describe using sonification, high-pitched sound waves like those in home ultrasonic
jewelry and denture cleaners, to break anti-cancer drugs into particles so small that thousands would
fit across the width of a human hair.
(19) Why is having high solubility in water important in drug development?
A The body’s enzymes use less energy to break it down
B It stays in the body longer
C It is least likely to interact with electrolytes
D It can become dissolved in the bloodstream
(20) Sonification breaks anti-cancer drugs into particles, this:
A Increases the surface area of the drug
B Makes the molecules travel faster
C Alters the blood pressure
D Remove more waste products
Short Answers:
(21) How are water molecules bonded through a hydrogen bond?
(22) What is the definition of solubility?
(23)What must happen in a solution in order to conduct electricity?
(24) Why does water have a high boiling point?
(25) How does one water molecule connect to other water molecules?
(26)What are 3 factors affecting the RATE of dissolving?
(27) What are the two components of a solution?
Essay questions:
(28) What causes water to be polar?
(29) Explain in detail the dissociation of an ionic compound by water molecules?
(30) Explain the difference between adhesion and cohesion of water.
(31) Explain why ice is less dense than liquid water (your answer should be explained from the
molecular point of view).
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Using the solubility graph above, answer the following questions:
(32)What is the solubility of the following solutes in 100mL of water at the following temperatures?
a. KNO3 at 70°C = ____________
b. NaCl at 100°C= ____________
c. NH4Cl at 90°C= ____________
(33) Which of the above three substances is most soluble in water at 15°C. = ______
(34) Determine whether the following will result in a saturated, unsaturated, or supersaturated
solutions:
a.
b.
c.
d.
A solution that contains 70g of NaNO3 at 30°C (in 100 mL H2O) _________________
A solution that contains 20g of KClO3 at 50°C (in 100 mL H2O)__________________
A solution that contains 50g of NH4Cl at 50°C (in 100 mL H2O)__________________
A solution that contains 70g of KI at 0°C (in 100 mL H2O)
__________________
(35) Explain how you would go about to make a supersaturated solution from scratch if all you
have available are 60.0 grams of KNO3 and water. Be very detailed in your explanation, include
amounts and temperatures.
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