Download Chemistry 100 G Homework 1

Chemistry 110 - 02
Fall 2016
Eighth Homework
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Finish studying Hill and McCreary Chapter 6 sections 1 - 5.
Study Hill and McCreary Chapter 7 sections 1, 2, and 4 - 6.
Begin to study Hill and McCreary Chapter 8 section 1.
Prepare for the next lab and write the lab report.
Begin reviewing for the final exam by reworking past homework and quiz questions. Review
memorized information like compound names, formulas for ions, etc.
The seventh quiz will include questions from the topics below and from the nineth homework. To be
prepared for the quiz, you should be able to answer these questions using only the periodic table you
received in class and the information given. Any quiz may include questions about lab safety and
procedures.
Due 8:30 am Wednesday, November 9. 10 Points.
Late homework is not accepted after 8:30 am Thursday, November 10.
1. Perform the following calculations.
a. What is the mass in grams of 0.392 moles magnesium hydroxide?
b. How many moles is 34.8 g H2SO4?
2. Write the formula for each of these compounds.
a. calcium fluoride
b. lithium phosphide
d. potassium chlorate
e. ammonia
c. magnesium nitride
f. sodium bicarbonate
3. Give the chemical formula for each of the following compounds.
a. potassium sulfide
b. ammonium sulfate
c. calcium phosphate
d. aluminum nitrate
e. magnesium hydroxide
f. lithium acetate
4. Classify each of these compounds as molecular or ionic.
a. CaF2
b. NH3
c. NH4Cl
d. HCl
5. Which of these statements are true?
a. Sometimes energy is released when a covalent bond is broken.
b. Oil molecules and water molecules repel each other when they get close together.
c. When water evaporates, it becomes hydrogen gas and oxygen gas.
d. The atoms present after a chemical reaction are the same as the atoms present before the
chemical reaction.
6. For each of these compounds, indicate whether London dispersion attractions, dipole-dipole
attractions, and/or hydrogen bonding are present between the molecules of the pure compound.
a. ethane (CH3CH3)
b. chloromethane (CH3Cl)
c. formaldehyde (H2CO)
d. methanol (CH3OH)
e. octanol (CH3CH2CH2CH2CH2CH2CH2CH2OH)
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7. Predict which compound in each pair will have the stronger intermolecular attractions.
a. ethane (CH3CH3) or octane (CH3CH2CH2CH2CH2CH2CH2CH3)
O
CH3 ) or propanol (CH CH CH OH)
b. acetone (H3C C
3
2
2
c. methane (CH4) or dichloromethane (CH2Cl2)
d. dichloromethane (CH2Cl2) or propane (CH3CH2CH3)
8. Predict which compound in each pair has the higher heat of vaporization.
a. ethane (CH3CH3) or octane (CH3CH2CH2CH2CH2CH2CH2CH3)
O
CH3 ) or propanol (CH CH CH OH)
b. acetone (H3C C
3
2
2
c. methane (CH4) or dichloromethane (CH2Cl2)
d. dichloromethane (CH2Cl2) or propane (CH3CH2CH3)
9. Predict which compound in each pair has the higher boiling point.
a. ethane (CH3CH3) or octane (CH3CH2CH2CH2CH2CH2CH2CH3)
O
CH3 ) or propanol (CH CH CH OH)
b. acetone (H3C C
3
2
2
c. methane (CH4) or dichloromethane (CH2Cl2)
d. dichloromethane (CH2Cl2) or propane (CH3CH2CH3)
10. Run the Intermolecular Attractions and Melting Point simulation on the class web page.
Explore how the strength of the intermolecular attractions affects the melting temperature. (Set
the Intermolecular Attractions to weak and find the temperature at which the solid melts. Repeat
with the Intermolecular Attractions set to medium and strong.) What is the relationship between
the strength of the intermolecular attractions and the melting temperature?
11. Draw a water molecule. Now draw four more water molecules around this first molecule,
showing the arrangement of the molecules. Use dashed lines to show the hydrogen bonding
attractions between the first molecule and the four surrounding molecules.
12. A drop of liquid water evaporates (becomes gas).
a. Sketch what the liquid looks like at the nanoscale. Show any hydrogen bonding attractions.
b. Sketch what the gas looks like at the nanoscale. Show any hydrogen bonding attractions.
(You might run the States of Matter – Molecular simulation to help with this. Increase the
temperature so the sample is a gas.) Remember that intermolecular attractions are present only
when the molecules are right next to each other.
13. Distilled water is very expensive because it takes a large amount of energy to convert liquid water
at 100 °C into gaseous water (steam) at 100 °C. This energy is called the heat of vaporization.
Explain what is happening at the nanoscale when liquid water becomes gaseous water and why
this change requires a large amount of energy. (You might run the States of Matter – Molecular
simulation to help with this.)
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14 For each of these compounds, indicate what types of intermolecular attractions are present
between the molecule listed and water molecules.
a. between ethane (CH3CH3) and water
b. between chloromethane (CH3Cl) and water
c. between formaldehyde (H2CO) and water
d. between methanol (CH3OH) and water
e. between octanol (CH3CH2CH2CH2CH2CH2CH2CH2OH) and water
f. between acetone (CH3COCH3, the 3 carbon atoms are bonded together. The oxygen is double
bonded to the central carbon.) and water
15. For each of these compounds, indicate whether it should be very soluble in water or not soluble.
a. ethane (CH3CH3)
b. chloromethane (CH3Cl)
c. formaldehyde (H2CO)
d. methanol (CH3OH) e. octanol (CH3CH2CH2CH2CH2CH2CH2CH2OH)
f. acetone (CH3COCH3, the 3 carbon atoms are bonded together. The oxygen is double bonded
to the central carbon.)
16. Proteins are made by creating covalent bonds between many amino acid molecules. In a protein,
the amino acids are bonded in one long chain. One part of each amino acid sticks out from the
chain, like charms on a charm bracelet. This part of the amino acid is called the “R group”. What
a protein does and how it works partly depends on the properties of these R groups. One
important property is the type of intermolecular attractions it has with water.
Four amino acid R groups are shown. For each, indicate whether or not the R group attracts water
via hydrogen bonding attractions.
H
a. valine:
H3C
c. phenylalanine:
b. glutamic acid:
C
O
CH3
H
H
C
H
O
H
H
C
C
C
H
H
d. threonine:
H
H
H
C
C
H
OH
17. The bond energy is the amount of energy needed to break the bond. A C-C single
bond has a bond energy of 347 kJ/mole. This means it takes 348 kJ of energy to
break one mole of C-C single bonds. The bond energy of a C=C double bond is 611
kJ/mole. This means that it takes 611 kJ/mole of energy to break both bonds in the
double bond.
a. How much energy does it take to break only the second bond in a C=C double
bond so that it ends with a C-C single bond? The bond energy of the double bond
(611 kJ/mole) is the sum of the bond energy of the single bond (347 kJ/mole) and
the bond energy of the second bond in the double bond.
b. How does the energy needed to break only the second bond compare to the energy needed to
break a C-C single bond?
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