Object A has twice the density, so it should have twice
the mass of an equal volume of object B. That’s why
(E) is right.
- C Remember q = mc∆T ? Substituting the values into it gives
30 cal = (15 g)(0.5 cal/g • °C) ∆T
Solve for ∆T, and you’ll get 4°C. This is the increase in
temperature. So if the substance was at 30°C, it’s now
at 34°C. That’s choice C.
- E Adding more oxygen gas will certainly increase the mass of the gas
sample; therefore, statement I is true.
Since density is the ratio of mass per volume,
increasing the mass while maintaining the same volume
will increase the density of the gas, so statement II is
also true.
Pressure is a measure of the force per unit area with
which gas molecules collide with the walls of the
vessel. More gas occupying the same volume will mean
more collisions and, therefore, greater pressure. So
statements I, II, and III are true, and (E) is the answer.
Notice that even if you don’t know if all of the
statements are true, you can make a really good guess
with just a little knowledge. Just knowing that
statement I is true allows you to eliminate choices B
and D, and by knowing that statement II is also true,
you can rule out choice A. At this point, you have a 50
percent chance of choosing the right answer even if you
know nothing about pressure!
