Chapter 3 Homework

Atoms: The Building Blocks of Matter – 5 points

__Read Pages 65-82__
and answer the following questions:
(Remember that “Think about it” questions are not necessarily answered
in the text and they are often good indicators of general quiz questions)

1. Around what year and which
philosopher first supported a particle theory of matter?

2. What famous philosopher did
not believe in atoms. (but his view
became accepted for 2000 yrs)

3. True or False: When elements combine to make a compound
they always do so in the same ratio.

4. What is the law of conservation
of mass?

5. NaCl is table salt. What percent is Na and what percent is Cl by
mass?

6. What is the law of definite
proportions? (see how it relates to
question #5)

7. True or False: An element can have atoms with different
masses.

8. What are the two regions of
atoms and what are contained in these regions?

9. What are the charges on the
three subatomic particles which make up atoms?

10. What is the charge of an anode
electrode?
What is the charge of a cathode electrode?

11. How did scientists
illustrate that cathode rays had mass?

12. How did scientists
illustrate that cathode rays were negatively charged?

13. What subatomic particle did
Joseph Thompson discover in cathode rays?

14. What did Robert Millikan
discover to be the mass of an electron? (in kg)

15. Did it matter which metal
they used for electrodes or gas in the tube?
Why would this be important?

16. What two other inferences
could scientists now make about the composition of an atom.

17. What did Rutherford, Geiger
and Marsden bombard with positive alpha particles in 1911?

18. After two years of
thinking, what explanation did Rutherford have for the results? (fig. 3-7)

19. True or False: The nucleus of an atom makes up the majority
of an atom’s volume.

20. If the nucleus of an atom
were the size of a marble, how big would the entire atom be?

21. True or False: Atoms contain the exact same number of
protons as electrons.

22. What is the mass of a
proton? How many times greater than the
mass of an electron?

23. What is the mass of a
neutron? Which subatomic particle is it
closest to in mass?

24. The number of __________ in
a nucleus determines that atom’s identity.

25. What percent of air is Ne
and how many Ne particles are in each breath you take?

26. What does the atomic
number tell you about an atom?

27. Think about it: What other
subatomic particle can be determined by the atomic number?

28. What’s an isotope and what
makes it an isotope?

29. What does the mass
number tell you about an atom?

30. What is the formula for
finding the # of neutrons from the mass # and the atomic #? (look at the
practice problems on p. 77-78, those will be on the quiz)

31. How much does one single
solitary atom of oxygen-16 weigh?

32. What is the standard atom
used to determine one atomic mass unit?

33. What is the average
atomic mass?

34. Find the weighted average
of 100 balls with a mass of 5.00 g each and 2 balls with a mass of 10.0 g each
(be sure to round to three significant digits)

35. How many numbers after the
decimal place should you round atomic masses?

36. What is a mole?

37. True or False: A mole is a weight

38. What is the numerical value
of the mole (also known as Avogadro’s number)

39. What is molar mass?

40. What are the units for
molar mass?

** **

** **

**ALWAYS REMEMBER: **

**1 mole = 6.02 x 10 ^{23} atoms (or molecules or formula units)**

** AND Grams ****ß****----****à**** Moles ****ß****---****à**** Molecules (or Formula units or atoms)**

**Mole:**

1. 3 moles of Magnesium has what mass?

2. 8 moles of Sodium has what mass?

3. 5 moles of Calcium has what mass?

4. How many moles are in 20.6 g of Magnesium?

5. How many moles are in 45.7 g of Sodium?

6. How many moles are in 89.6 g of Calcium?

7.
If you have 5.67 x 10^{28 }atoms of Magnesium, how many moles is
this?

8.
If you have 3.25 x 10^{29 }atoms of Sodium, how many moles is
this?

9.
If you have 7.52 x 10^{31 }atoms of Calcium, how many moles is
this?

10. If you have 2.23 x 10^{28 }molecules of water, how many
moles is this?

11. If you have 9.63 x 10^{22 }formula units of sodium
chloride, how many moles is this?

12. If you have 5.67 x 10^{32 }formula units of Magnesium
Hydroxide, how many moles?

13. If you have 4.00 moles of Magnesium, how many atoms is this?

14. If you have 5.90 moles of Sodium, how many atoms is this?

15. If you have 7.00 moles of Calcium, how many atoms is this?

16. If you have 4.50 g of Magnesium, how many atoms is this?

17. If you have 6.70 g of Sodium, how many atoms is this?

18. If you have 5.60 g of water, how many molecules is this?

19. If you have 9.00 g of Magnesium hydroxide, how many formula units is this?

20. If you have 5.67 x 10^{28 }atoms of Magnesium, how many
grams is this?

21. If you have 3.25 x 10^{29 }atoms of Sodium, how many
grams is this?

22. If you have 7.52 x 10^{31 }atoms of Calcium, how many
grams is this?

23. If you have 2.23 x 10^{28 }molecules of water, how many
grams is this?

24. If you have 9.63 x 10^{22 }formula units of sodium
chloride, how many grams is this?

25. If you have 5.67 x 10^{32 }formula units of Magnesium
Hydroxide, how many grams?

Also, from the book, do the following: (The answers are in the book – And, there are sample problems before each of these.)

p. 222 Practice problem #1

p. 223 Practice problems #1-2

p. 226 Practice problems #1-2

Answers to chapter 3 homework.

Converting grams to moles to molecules

1.
72.9g

2.
184g

3.
201g

4.
0.848mol

5.
1.99mol

6.
2.23mol

7.
94200mol

8.
540000mol

9.
1.25 x 10^{8}mol

10.
3.70 x 10^{4}mol

11.
0.160mol

12.
9.42 x 10^{8 }mol

13.
2.41 x 10^{24 }atoms

14.
3.55 x 10^{24 }atoms

15.
4.21 x 10^{24 }atoms

16.
1.11 x 10^{23 }atoms

17.
1.75 x10^{23 }atoms

18.
1.87 x 10^{23 }mol

19.
9.29 x 10^{22 }form. Units

20.
2.29 x 10^{6 }g

21.
1.24 x 10^{7 }g

22.
5.01 x 10^{9 }g

23.
6.67 x 10^{5 }g

24.
9.36g

25.
5.49 x 10^{10 }g