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1. A chemical reaction produces a gas that forms a
spherical balloon with a radius of 10 cm. What is the
volume of the gas inside the balloon? Use the formula V =
(4/3)Àr^3 for the volume of a sphere.
a) 314 cm^3
b) 4188 cm^3
c) 1257 cm^3
d) 628 cm^3
Answer: B. The volume of the gas is equal to the volume of
the sphere, so we plug in r = 10 into the formula and get V
= (4/3)À(10)^3 = 4188 cm^3.
2. A chemist wants to measure the distance between two
atoms in a molecule using a microscope. The microscope
has a magnification of 1000x and the atoms appear to be 2
mm apart on the screen. What is the distance
between the atoms in nanometers? Use the fact that 1 mm =
10^6 nm.
a) 2 nm
b) 2000 nm
c) 0.002 nm
d) 0.2 nm
Answer: C. The distance between the atoms is equal
to the apparent distance divided by the magnification, so
we divide 2 mm by 1000 and get 0.002 mm. Then we
multiply by 10^6 to convert to nanometers and get 0.002
nm.
3. A chemical compound has a molecular formula ofÂÂ
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