Chemistry without it we wouldn’t know how the

Chemistry Mid-term Exam                                                                            Version
11/2016

Name: Emma Ross

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Directions:  It is important that you provide answers
in your own words.  Please focus only on
information from the text/eBook to create your own solutions.  Please do
not use direct information from an outside source (especially copying and
pasting from an “answer” website). Use of direct information from an outside
source is against school policy.  All answers will be checked for
plagiarism.  Instances of plagiarism can
result in probation or possible dismissal from the school.

Please be sure to follow all guidelines (number of sentences/showing
all calculations) and to provide the correct metric units of measure.  All questions are 3.33 points (.33 point for units).

 

 

1.    
Experimental
Design:  From the work you have done this
semester, choose a topic and design an experiment you would be able to
perform.  In your design (1) state your
hypothesis, (2) identify your dependent and (3) independent variables, (4) your
control conditions and (5) describe your experimental procedure.  You do NOT have to actually complete the experiment,
just describe it with the application of the terms above.

 

 

 

2.    
Perform
this operation and report the answer to the correct number of significant
figures:  What is the mass of a cube
of aluminum that is 4.0 cm on each edge? 
The density of aluminum is 2.7 g/cm3.  Show all calculations leading to an answer.

The volume of the
cube (V) is:

V=a^3       (a – the side of the cube)

The density (D)
is the quotient of mass (m) and volume (V):

D = m/V = m/a^3

M=d*a^3

 

 

D=2.7 g/cm^3

A=4cm

M=D*a^3=2.7*4^3=172.8g

 

 

3.  Explain why a model of the
atom is crucial to understanding chemistry and in explaining the behavior of
matter.  Use 3 – 4 sentences in your explanation.

The model of the
atom is crucial because without it we wouldn’t know how the protons, neutrons,
and electrons are connected. Essentially, the protons and neutrons are seen
with their bonds while electrons are rotating waves of energy that go around
the atom. This model helps us differentiate different elements and isotopes
based on the number of components and the way they are connected.

 

4.    
What
parts of Dalton’s atomic theory no longer agree with the current picture of the
current picture of the atom? Provide an answer using at least 3 to 4 complete
content related sentences in your own words.

 

Dalton’s
atomic theory doesn’t comply to our latest picture of the atom we have

today. Dalton stated that atoms were the
smallest particles in the universe and you

can’t split them, but in fact you can
split them into tinier particles which are the

electrons neutrons and protons.

 

5.    
If
an element has 12 protons and 17 neutrons, how many electrons must it have?

 

12 electrons

6.    
Why
are the atomic masses of elements usually decimal numbers? Provide an answer
using 3 – 4 sentences in your own words.

The atomic mass is more exact in decimals because they are usually

nonterminating numbers. So, because they
are nonterminating and exact numbers,

they always round up to the nearest thousandth

 

7.    
In
3 – 4 sentences and in your own words describe how Mendeleev’s periodic table differs
from Moseley’s.

Mendeleev
arranged the table by mass leaving spaces for the undiscovered

elements
while Moseley arranged it by atomic number. Mendeleev also arranged them by

property
similarities and atomic weight and did not include the noble
gases yet because

they
weren’t discovered yet. Moseley had fixed Mendeleev’s mistakes and adjusting
the

periodic table and
arranged them by increasing atomic number

 

8.    
What
is the electron configuration of the element with 27 protons?

1s2
2s2 2p6 3s2 3p6 3d7 4s2

 

9.    
How
many electrons are in the highest energy
orbital of the element copper?

Copper
only has 1 electron in its highest energy orbital

 

10.  How many dots should be indicated in
the electron dot structure of arsenic?

5

 

11.  Why is the first ionization energy of
a nonmetal much higher than that of an alkali metal in its same period? Provide
an answer using 3 – 4 sentences in your own words.

Nonmetal’s
shells are a lot more full than alkali’s shells making it much harder

to
remove electrons. This is because any nonmetal’s atom
is a lot smaller than an

alkali metal’s atom,
therefore the denser, the harder it is to remove electrons

Why
do compounds with strong intermolecular attractive forces have higher boiling
points than compounds with weak intermolecular attractive forces? Provide an
answer using 3 – 4 sentences and in your own words.

 

 

12.  Write the formula for iron (III)
sulfate.

Fe2(SO4)3

 

 

13.  What is the reason the group 13
metals have a typical charge of 3+?

 

Because all these
elements have 3 electrons in their valence shell.

 

When they lose
the 3 valence electrons, acquire a 3+ charge and get the electron configuration
of the lower Noble gas in the periodic table, this is with the outermost shell
full, which is very energetically favorable.

 

14.  Why does one mole of carbon atoms
have a smaller mass than one mole of sulfur atoms?

The molar mass (grams per one mol) or Carbon is less then Sulfur because Sulfur has more protons. If you had a
mole of Carbon you would have 12g whereas if you had a mole of Sulfur you would
have 32 g. Carbon has 6 protons and Sulfur has 16. Protons make up most of the
mass of an atom, therefore, more protons more mass.

 

15.  What is the percentage of nitrogen in
N2O?  Show all calculations
leading to an answer.

The
gram formula mass of N2O is 14*2+16=44. The mass of 2 nitrogen atom is 14*2=28.
So the percentage is that 28/44*100%=63.6%.

16.  How many non-bonding electrons does
phosphorus have?

 

15

 

17.  Complete and balance this reaction: 
sulfuric acid reacts with barium chloride

H2SO4
+ BaCl2 —- 2HCl + BaSO4

 

 

18.  Identify the precipitate in this
reaction:  calcium nitrate reacts with
sodium phosphate.

3Ca(NO?)?(aq)
+ 2Na?PO?(aq) ? Ca?(PO?)?(s) + 6NaNO?(aq)

 

3Ca²?
+ 6NO?? + 6Na? + 2PO?³? ? Ca?(PO?)? + 6Na? + 6NO??

 

3Ca²? + 2PO?³? ? Ca?(PO?)?

 

 

19.  The following is a Limiting Reactant
problem:

Magnesium
nitride is formed in the reaction of magnesium metal with nitrogen gas in this
reaction:  3 Mg(s) + N2(g)
à Mg3N2(s)

            How many grams of product are formed
from 2.0 mol of N2 (g) and 8.0 mol of Mg(s)?                       Show all calculations leading to an
answer.

Mole Ratio of Mg : Mg3N2 = 3 b: 1 ?

?mole of Mg3N2 =
moleofmagnesium over 3 = 8.0mol over 3 = 2.67 mol ?

?mass of Mg3N2 = mole * molar
mass = 2.67 mol * ((3* 24) + (2 * 14)) g / mol = 2.66.67 ?

 

20. 
List 3 indicators of a chemical change.

a.   
Change in color

b.   
Change in temperature

c.   
Change in odor

 

21. 
Check the
following problem for errors. If you find an error, identify it, tell why it is
an error and correct the error solving the problem correctly.  Convert 0.45 g zinc hydroxide to moles. (Hint: there are errors)

 

0.65
g ZnOH            82.41 mol        = 3.22 X 10 25 mol

                                 6.02X1023
g

 

Zinc hyrdoxide is Zn(OH)2 and it’s molar mass is 99.42
grams/mole. The conversion is done like this:

0.45 g Zn(OH)2 x (1 mole / 99.42 g) = .0045 mole Zn(OH)2

The error is in the mass, the chemical formula, and the
molar mass of zinc hydroxide.

 

 

 

22.  What
is an ion?  Explain how ions form.
Distinguish between a cation and an anion. Be sure to use at least 3 to 4
complete content related sentences in your explanation.

An ion is considered to be an atom which will be
giving or indicate an electric charge of whether it will be positive or
negative. The ions will only be formed when the atom that it obtains will bring
out either a gain or lose in its electrons. The electively charge ions are classified
into two which are called the cation and anion. The cation is classified as the
positive charge, while the anion is classified as the negative charge ion. They
are the ones responsible for providing electric charge on the ion.

23.  Write
the symbol for the ion formed when each element gains electrons and attains a
noble-gas electron configuration.

a.    
Br

Br1-

b.    
H

H1+

c.    
Se

Se2-

 

24.  Name
each of the compounds.  There are ionic,
covalent and acid/base compounds in the list.

a.    
N2H4

dinitrogen
tetrahydride

b.    
PI3

phosphorus tri-iodide

c.    
LiOH

Lithium hydroxide

25.  Classify
each chemical equation as a combination/synthesis , decomposition, single
replacement, double replacement, or combustion.

 

a.    
Pb(s) + Hg2SO4(s) à
PbSO4(s) +2 Hg(l)

Single replacement

b.      NaCl(aq) + AgNO3(aq) à
AgCl(s) + NaNO3(aq)

Double replacement

c.     2
H20(l)à2
H2(g) + 02(g)

decomposition

            

26. Find the molar mass of
nitric acid (HNO3).

H = 1.008

N =
14.007

O3 =
15.999*3= 47.997

 

HNO3 = 63.012g/mol

 

27. 
Avogadro’s
number refers to ___.

a.    
the
maximum number of electrons that all of an atom’s energy levels can accommodate

b.    
the
number of protons and neutrons that can fit in the shells of an atom’s nucleus

c.    
the
number of particles in one mole of a substance

d.    
the
number of particles in exactly 1.0 g of a substance

 

C

 

28.   How many moles of oxygen atoms are in 1.5
moles of CO2? (Sc2c)

a.    
1 mol                       b.
1.5 mol             c. 2 mol                                    d. 3 mol

 

D

 

29.  What
is the mass of 0.28 mol of iron ?

Mass =
number of mol x molar mass

Mass =
0.28mol x 55.8g/mol

Mass = 15.624g

x

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