PreAP Chemistry
KEY
Fall Final Review
1.
What is the difference between a hypothesis and a theory?
A hypothesis is an UNTESTED explanation – based on
observations. A theory is a thoroughly tested
explanation that is believed by many.
2.
Contrast a theory and a scientific law.
While a theory is a possible explanation, a law is just a
description of natural phenomena (usually
mathematic).
3.
How does precision relate to significant digits and scientific instruments?
Instruments that are more precise produce
measurements with more significant digits.
4.
How would 0.000053701 be written in scientific notation?
5.3701 x 10-5
5.
How many significant digits are in the following number?
0.0803000
6.
=
6
List chemical properties of iron? Why are these chemical properties and not
physical?
Reactivity with water, air, acid, etc. These are chemical
because the pure iron would change into some other
substance (like rust) if the property was observed.
7.
How is a mixture different than a compound?
A mixture can have varying amounts of parts (like
Kool-Aid) but a compound is ALWAYS made of the
same elements in the same ratios (H2O).
8.
List two things that are not samples of matter?
(any form of energy)
9.
Which phase of matter is fluid, takes the form of its container, and yet has
definite volume?
liquid
10. What will happen when a positively charged particle comes into contact
with another positively charged particle?
They will repel each other.
11. Explain the law of definite proportions.
Compounds are always made of the same elements in
the same fixed ratios.
12.
What are the postulates of Dalton’s model?
- All matter is made of indivisible atoms.
- All atoms of an element were identical.
- Each element has different sized atoms (from other
elements).
- Compounds consisted of atoms of different elements
combined together in specific ratios
- Chemical reactions involved the rearrangement of
combinations of those atoms.
13. Explain how Dalton attempted to explain the Law of Conservation of Mass
with his postulates.
Since atoms are indivisible, when reactions occur (the
rearrangement of atoms) the individual atoms are not
changed. Mass stays the same.
14. How did the results of the CRT experiment lead to Thomson’s theory of the
atom?
The beam in the CRT was attracted to a positive charge
and repelled by a negative one so Thomson concluded
that the beam was made of negatively charged
particles. Thomson knew these particles must be part
of the metal atoms making up the anodes of the tube.
15.
Why did Thomson revise his theory to state that the “shell” of the atom
was positively charged?
If the atom contained only negatively charged
particles, then all matter would have a negative charge.
16. What did Rutherford conclude about the deflection of alpha particles in the
“gold foil” experiment?
Since the alpha particles were positively charged and
fast moving, they must have been deflected by
something more massive that was positively charged.
17. What experimental evidence lead him to believe that much of the atom was
empty space?
The vast majority of the alpha particles went right
through the gold foil.
18.
Bohr suggested that the spectral lines of hydrogen were evidence of energy
released by the atoms as an electron moved from ___________________ to
____________________ and back again.
Lower energy levels (ground state)
Higher energy levels (excited state)
19. Bohr’s model added energy levels to the theory of atoms. How many
electrons can exist in the first energy level of an atom?
2
20. What would be the electron configuration for phosphorus?
1s22s22p63s23p3
21.
What is the identity of the following element?
1s22s22p63s23p64s23d104p2 =
Germanium
22. How many “p” sublevels would be in a bismuth atom?
5
23. How many filled orbitals would be in a titanium atom?
11
24. How many “d” orbitals can be in an energy level? How many “d” electrons
can there be in an energy level?
5, 10
25. Give the electron configurations of the following elements:
a. Strontium
b. Bromine
c. Iron
d. Cadmium
26.
1s22s22p63s23p64s23d104p65s2
1s22s22p63s23p64s23d104p5
1s22s22p63s23p64s23d6
1s22s22p63s23p64s23d104p65s24d10
Are the majority of the elements on the periodic table metals or nonmetals?
Metals
27. Explain “alpha” radiation. What is emitted and which elements go through
alpha decay?
Alpha radiation is the expulsion of a particle from the
nucleus that contains two protons and two neutrons. It
is dense, positively charged, and fast moving.
Elements BEYOND #83 go through alpha decay.
28. How is positron emission different from beta decay? How would you
know which isotopes would go through which form of decay?
Positron emission is the loss of a positive particle from
the nucleus while beta emission is the loss of a
negative particle (electron). Isotopes above the belt of
stability go through beta emission and those below
emit positrons.
29. How is gamma radiation different from beta radiation?
Gamma radiation is actually a wave of energy while
beta radiation is an emitted particle.
30. Describe the trends of metallic nature AND reactivity on the periodic table.
Elements get more metallic to the left and down.
Reactivity increases from the middle out (up and to the
right – down and to the left.