Download Honors Midterm - Stamford High School

Honors Review Form C (Chapter 7,8,9, 11, and a smidget of 10)
1)Identify the # of electrons in the following anions, cations and neutral atoms ; write their electron
configuration
# of Electrons
Electron Configuration
Magnesium
12
1s2, 2s2, 2p6, 3s2
Magnesium ion
10
1s2, 2s2, 2p6
Chlorine
17
1s2, 2s2, 2p6, 3s2, 3p5
Chlorine
18
1s2, 2s2, 2p6, 3s2, 3p6
2)What is a cation? An ion with a positive charge. Metals form cations
3)What is an anion? An ion with a negative charge. Non-metals form anions
4)Define the following be sure to describe what they are composed of and how it is formed,
Ionic compound – a compound consisting of a metal and a non-metal with a bond that is formed by
transferring electrons
Covalent compound – a compound formed between two or more non-metals with bonds that are
formed by sharing electrons.
Metallic compound – a compound formed between metals with bonds that consist of the attractions
of the free-floating valence electrons for the positively charged metal ions.
5)Must be able to name and write formulas for ionic and covalent compounds.
Write the formula for:
a. potassium fluoride - KF
e. carbon disulfide – CS2
b. sodium sulfate - Na2SO4
f. tetraphosphorus hexaoxide – P4O6
c. lead (II) iodide PbI2
g. silicon tetrafluoride - SiF4
d. barium phosphate – Ba3(PO4)2
h. potassium nitrite – KNO2
6)For the following: draw the lewis structures, figure out how many bonds are needed to satisfy the
octet rule, figure out how many lone pair are part of a molecule and whether or not it is polar.
CO2 –
BF3
CH4
4 lone pairs, linear, non polar molecule
9 lone pairs, trigonal planar, non-polar molecule
0 lone pairs, tetrahedral, non-polar molecule
H20
PF5
NH3
2 lone pairs, bent, polar
molecule
one lone pair, pyramidal, polar molecule
CCl4
CHCl3
12 lone pairs, tetrahedral, non polar molecule
9 lone pairs, tetrahedral, polar molecule
CH2O
Two lone pairs, trigonal planar,
polar molecule
7)What are the differences between an ionic and a covalent bond?
Characteristic
Ionic Compound
Covalent compound
Representative unit
Formula unit
Molecule
Bond formation
Transfer of one or more
electrons between atoms
Sharing of electron pairs
between atoms
Type of elements
Metallic and nonmetallic
Nonmetallic
Physical state
Solid
Solid, liquid and gas
Melting point
High (usually above 300 C)
Low (usually below 300 C)
Solubility in water
Usually high
High to low
Electrical conductivity of
aqueous solution
Good conductor
Poor to non-conducting
8)What is metallic bond? Why are metals such good conductors and what makes metals shiny?
Metallic bonds consist of the attractions of the free-floating valence electrons for the positively
charged metal ions. The free floating valence electrons make metals good conductors and light
reflecting off of the free floating valence electrons that travel around the outside of metal give metal
its luster (shine).
9)What value makes a bond polar or non-polar or ionic? (see table 8.3 on page 238)
10)Balance a chemical equation using coefficients (see worksheet I will give out in class today).
Some balancing chemical equation rules from Mrs. Kaiser:
Listen: There are four easy steps that you need to follow to make this work. Here they are:
1. Get yourself an unbalanced equation. I might give this to you, or I might make you figure it
out.
2. Draw boxes around all the chemical formulas. Never, ever, change anything inside the boxes.
Ever. Really. If you do, you're guaranteed to get the answer wrong.
3. Make an element inventory. How are you going to know if the equation is balanced if you
don't actually make a list of how many of each atom you have? You won't. You have to make
an inventory of how many atoms of each element you have, and then you have to keep it
current throughout the whole problem.
4. Write numbers (coefficients) in front of each of the boxes until the inventory for each element
is the same both before and after the reaction. Whenever you change a number, make sure to
update the inventory - otherwise, you run the risk of balancing it incorrectly. When all the
numbers in the inventory balance, then the equation can balance. Hurray! Congratulations
now you can relax.
5. See your balancing equations worksheet for more examples
See your book page 324 – 327.
11)What is catalyst? It is a substance that is added to chemical reactions that increase the rate of the
chemical reactions. The catalyst is not used up by the chemical reactions and is reusable. The catalyst
is written above the arrow in a chemical reaction.
12)What are the different types of chemical reactions? And give an example of each type of reaction
Combination Reactions – is a chemical change in which two or more substances react to form a
single new substance.
Ex. S(s) + O2(g)  SO2(g) sulfur dioxide
Ex. 2S(s) +3O2(g)  2SO3(g) sulfur trioxide
Decomposition Reaction – is a chemical change in which a single compound breaks down into
two or more simpler products.
Ex. 2HgO(s)  2Hg(l) + O2(g)
Single Replacement Reaction – is a chemical change in which one element replaces a second
element in a compound. You can identify a single replacement
reaction by seeing that the reactants and the products consist of an
element and a compound.
Whether one metal will displace another metal from a compound depends upon the relative
reactivities of the two metals. The activity series of metals, given in Table 11.2, lists metals in
the order of decreasing activity.
Ex. Br2(aq) + NaI(aq)  NaBr(aq) + I2(aq)
Ex. Br2(aq) + NaCl(aq)  No Reaction
Double Replacement Reaction – is a chemical change involving an exchange of positive ions
between two compounds.
Ex. Ca(OH)2(aq) + 2HCl(aq)  CaCl2(aq) + 2H2O(l)
Combustion Reactions – is a chemical change in which an element or a compound reacts with
oxygen, often producing energy in the form of light and heat.
Ex. 2C8H18(l) + 25O2(g)  16CO2(g) + 18H2O(l)
13)Given the beginning of a combustion reaction identify the products of the reaction.(complete
combustion)
The products of a combustion reaction are CO2 and H2O
14)What is the molar mass(formula weight) of
a. H20 = 18 g/mol
b. CO2 = 44 g/mol
c. NaCl = 58.45 g/mol
15)One mole of anything contains 6.02 x 10 23 atoms. This number is called avagadro’s number.
(chapter 10)
16)Why did we balance the chemical equations?
Chemical equations are balanced to obey the law of conservation of mass. On each side of the
equation there are the same number of atoms of each element.
17)CAPT Acid Rain Lab - Go over this experiment and think about it in terms of the scientific method.
Did you have enough information to replicate the experiment? If not what other information would
you need? Give two pieces of information that are needed or that you have? How would you improve
this experiment to improve validity? What was the independent and dependent variables in this
experiment?
- Not enough information was collected to replicate this experiment.
- Needed mass of stones, more time to complete the lab, etc.
Improvements to this lab (this would be your ideas and scientific reasoning)
Independent variable: Type of Stones
Dependent variable: pH and physical observation of the stones