New SAT Reading Practice Test 52: Paired Passages—Acidity

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Paired Passages—Acidity

Passage 1

In the past century, due to the burning of
fossil fuels in energy plants and cars, acid rain
has become a cause of harm to the environment.
However, rain would still be slightly acidic even if
05these activities were to stop. Acid rain would con-
tinue to fall, but it would not cause the problems
we see now. The environment can handle slightly
acidic rain; it just cannot keep up with the level of
acid rain caused by burning fossil fuels.
10A pH of 7 is considered neutral, while pH below
7 is acidic and pH above 7 is alkaline, or basic.
Pure rain water can have a pH as low as 5.5. Rain
water is acidic because carbon dioxide gas in the air
reacts with the water to make carbonic acid. Since
15it is a weak acid, even a large amount of it will not
lower the pH of water much.
Soil, lakes, and streams can tolerate slightly
acidic rain. The water and soil contain alkaline
materials that will neutralize acids. These include
20some types of rocks, plant and animal waste, and
ashes from forest fires. Altogether, these materials
can easily handle the slightly acidic rain that occurs
naturally. The alkaline waste and ashes will slowly
be used up, but more will be made to replace it.
25Anthropomorphic causes of acid rain, such as
the burning of fossil fuels, release nitrogen oxide
and sulfur oxide gases. These gases react with water
to make nitric acid and sulfuric acid. Since these
are both strong acids, small amounts can lower
30the pH of rain water to 3 or less. Such a low pH
requires much more alkaline material to neutral-
ize it. Acid rain with a lower pH uses up alkaline
materials faster, and more cannot be made quickly
enough to replace what is used up. Soil and water
35become more acidic and remain that way, as they
are unable to neutralize the strong acid.

Passage 2

In humans, keeping a constant balance between
acidity and alkalinity in the blood is essential. If
blood pH drops below 7.35 or rises above 7.45,
40all of the functions in the body are impaired and
life-threatening conditions can soon develop. Many
processes in the body produce acid wastes, which
would lower the pH of blood below the safe level
unless neutralized. Several systems are in place
45to keep pH constant within the necessary range.
Certain conditions, however, can cause acids to be
made faster than these systems can react.
Most of the pH control involves three related
substances: carbon dioxide, carbonic acid, and
50bicarbonate ions. Carbonic acid is formed when
carbon dioxide reacts with water. Bicarbonate
ions are formed when the carbonic acid releases a
hydrogen ion. Excess carbonic acid lowers the pH,
while excess bicarbonate ions raise it.
55The kidneys store bicarbonate ions and will
release or absorb them to help adjust the pH of
the blood. Breathing faster removes more carbon
dioxide from the blood, which reduces the amount
of carbonic acid; in contrast, breathing more slowly
60has the opposite effect. In a healthy body, these
systems automatically neutralize normal amounts
of acid wastes and maintain blood pH within the
very small range necessary for the body to function
normally.
65In some cases, these systems can be overwhelmed.
This can happen to people with diabetes if their
blood sugar drops too low for too long. People with
diabetes do not make enough insulin, which the
body uses to release stored sugar into the blood to
70supply the body with energy. If a person's insulin
level gets too low for too long, the body breaks down
fats to use for energy. The waste produced from
breaking down fats is acidic, so the blood pH drops.
If the kidneys exhaust their supply of bicarbonate
75ions, and the lungs cannot remove carbon dioxide
fast enough to raise pH, all of the other functions in
the body begin to fail as well. The person will need
medical treatment to support these functions until
the pH balancing system can catch up. The system
80will then keep the blood pH constant, as long as the
production of acid wastes does not exceed the body's
capacity to neutralize them.

1. Passage 1 most strongly suggests that

  • A. the environment will be seriously damaged if people do not reduce the burning of fossil fuels.
  • B. scientists must find a way to introduce more alkaline materials into the water supply to combat acid rain.
  • C. acid rain will not be a problem in the future as we move away from fossil fuels and toward alternative energy sources.
  • D. acidic rain water is more of a problem than acidic soil because soil contains more alkaline materials.

2. Which choice provides the best evidence for the answer to the previous question?

  • A. Lines 7-9 ("The environment … fuels")
  • B. Lines 12-14 ("Rain water … acid")
  • C. Lines 17-18 ("Soil, lakes … rain")
  • D. Lines 25-27 ("Anthropomorphic … gases")

3. According to the information in Passage 1, which pH level for rain water would cause the most damage to the environment?

  • A. 2.25
  • B. 4
  • C. 5
  • D. 9.1

4. As used in line 17, "tolerate" most nearly means

  • A. accept.
  • B. endure.
  • C. acknowledge.
  • D. distribute.

5. Passage 2 most strongly suggests that

  • A. a pH of 7.35 is ideal for blood in the human body.
  • B. acid wastes in the blood multiply if not neutralized.
  • C. the normal range of blood pH narrows as a person ages.
  • D. small amounts of acid wastes in the blood are a normal condition.

6. Which choice provides the best evidence for the answer to the previous question?

  • A. Lines 38-41 ("If blood pH … develop")
  • B. Lines 46-47 ("Certain conditions … react")
  • C. Lines 60-64 ("In a healthy … normally")
  • D. Lines 67-70 ("People with … energy")

7. As used in line 74, "exhaust" most nearly means

  • A. fatigue.
  • B. consume.
  • C. deplete.
  • D. dissolve.

8. Which of the following plays a role in the environment most similar to the role played by excess bicarbonate ions in the blood?

  • A. Acid rain
  • B. Ashes from a forest fire
  • C. Sulfur oxide gases
  • D. Fossil fuels

9. Based on the information in Passage 2, which of the following can cause the body to break down fats to use for energy?

  • A. An excess of carbonic acid
  • B. Low blood pH
  • C. A drop in blood sugar
  • D. Not enough insulin

10. Which of the following best describes a shared purpose of the authors of both passages?

  • A. To encourage readers to care for delicate systems such as the environment and human body
  • B. To explain how the human body neutralizes acid wastes that it produces and deposits in the blood
  • C. To describe systems that can neutralize small amounts of acids but become overwhelmed by large amounts
  • D. To persuade readers to work toward reducing acid rain by cutting consumption of fossil fuels

11. Both passages support which of the following generalizations?

  • A. The human body and environment are delicate systems that require balance to function properly.
  • B. There are many similarities between the systems that make up the human body and the water cycle.
  • C. Acid rain is an important issue that will continue to impact the environment until we reduce the use of fossil fuels.
  • D. Medical treatment is necessary when the pH of a person's blood drops below 7.35 or rises above 7.45.