An arco book arco is a registered trademark of Thomson Learning, Inc., and is used herein under license by Peterson’s. About The Thomson Corporation and Peterson’s

particles (
4
2 
He) is fired at
scattered when they hit an
high velocity against a sheet
electron because an electron
of gold foil, a few particles
is so small very few alpha
are scattered at large angles
particles collide with one.
This question refers to Rutherford’s famous experiment that provided seminal knowledge about
atomic structure. The assertion expresses what Rutherford did and observed. Rutherford made this obser-
vation because alpha particles that collided with the heavy, compact nuclei were scattered at large angles.
Since the nucleus is very compact few alpha particles are scattered at large angles. An electron is much
too small to scatter an alpha particle at a large angle.

---

Chemistry Subject Test
283
ARCO
■ SAT II Subject Tests
w w w . p e t e r s o n s . c o m / a r c o
5-Choice Completion Questions
Finally, the Chemistry Test also uses ordinary multiple-choice questions:
EXAMPLE:
__Cu(OH)
2
+ __N
2
H
4
= __Cu + __N
2
+ __H
2
O
When 96g of N
2
H
4
are consumed, how many grams of H
2
O are produced?
(A) 164g
(B) 180g
(C) 216g
(D) 236g
(E) 256g
The correct answer is (C). The first step in solving a stoichiometric problem is to balance the equation.
The balanced equation is 2Cu(OH)
2
+ N
2
H
4
= 2Cu + N
2 
+ 4H
2
O. From the balanced equation, we see that
for every mole of N
2
H
4
consumed there are 4 moles of H
2
O produced. The amount of N
2
H
4
consumed
is 96g; the molecular weight of N
2
H
4
= 32. Therefore, three moles of N
2
H
4
are consumed. If three moles
of N
2
H
4
are consumed, then 12 moles of water are produced. Twelve moles of water is 216g.
EXAMPLE:
If the total kinetic energy of one mole of helium molecules at 300
°K is 3.74 × 10
10
ergs, then
what is the total kinetic energy of two moles of oxygen molecules at 300
°K? (Atomic weights: He
2
= 4;
O
2
= 32)