ChemistryGoodInfo Chemistry I Exam 2

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Chemistry 2031 Chemistry I Exam 2 ( 100 points)

Name ______________________

SSN ______________________

Directions: Circle the correct answer (for your records) and fill in the

appropriate blank on the SCANTRON form. 40 points total – 2 points per

question

1. Classify the following reaction:

H2SO4(aq) + 2NaOH(aq) ==> 2H2O(l ) + Na2SO4(aq)

a) acid-base neutralization reaction

b) precipitation reaction

c) reduction-oxidation reaction

d) none of the above


NaHSO4(aq) + NaOH(aq) ==> H2O(l ) + Na2SO4(aq)








MgSO4(aq) + 2NaOH(aq) ==> Mg(OH)2( s) + Na2SO4(aq)





4. What is the net ionic equation for problem #1

a) 2H+(aq) + SO42-(aq) + 2Na+(aq) + 2OH-(aq) ==> 2H2O(l ) +

2Na+(aq) +SO42-(aq)

b) H2SO4(aq) + 2NaOH(aq) ==> 2H2O(l ) + Na2SO4(aq)

c) 2H+(aq) +2OH-(aq) ==> 2H2O(l )

d) H+(aq) +OH-(aq) ==> H2O(l )


H2SO4(aq) + Na( s) + H+(aq) ==> NaOH(aq) + H2SO3(aq)







6. What is the oxidation number (state) on N in HNO3?

a) +7

b) +6

c) +5

d) +4

7. Pick the correct products for the following unbalanced reaction:

FeCl2(aq) + KOH(aq) ==>

a) FeOH( s) + KCl(aq)

b) Fe(OH)2(aq) + KCl( s)

c) Fe(OH)2(aq) + KCl(aq)

d) Fe(OH)2( s) + KCl(aq)

8. Use the activity series of metals to predict the outcome of this

reaction:

Fe2+(aq) + Zn( s) ==>

a) Fe2+(aq) + Zn2+(aq)

b) Fe( s) + Zn2+(aq)

c) Fe( s) + Zn( s)

d) No reaction



9. What is the total molar concentration of all ions (positive and

negative) for a 0.225 M solution of K 2CO3 assuming complete

dissociation?

a) 0.225 M

b) 0.450 M

c) 0.675 M

d) 0.900 M

10. Which species is reduced in the following redox reaction?

2Na( s) + Zn2+(aq) ==> 2Na+(aq) + Zn( s)

a) Na( s)

b) Zn( s)

c) Zn2+(aq)

d) Na+(aq)

11. In problem 10 how many moles of electrons are transferred for

each mole of Zn2+ that is consumed in the reaction?

a) 1

b) 2

c) 3

d) 4

12. What is the valence shell electron configuration of Cl?



a) 3s7

b) 2s2 2p5

c) 3p7

d) 3s2 3p5

13. When do electrons emit light?

a) when they move to a higher energy level

b) when they move to a lower energy level

c) when they move to an equivalent energy level

d) all of the above

14. Pick the incorrect statement about electromagnetic radiation

a) All electromagnetic radiation travels at the same speed.

b) The energy of electromagnetic radiation decreases with

increasing wavelength.

c) Electromagnetic radiation behaves as both a particle and a

wave.

d) A beam of electromagnetic radiation is composed of a stream

of particles called photons.

e) all of the above are correct

15. Pick the correct statement about the Heisenberg Uncertainty

Principle.



a) One can never know both the position and velocity of an

electron beyond a certain level of precision.

b) The velocity of an electron will never be known.

c) The position of an electron will never be known.


16. The principal quantum number (n) describes what?

a) the three-dimensional shape of the orbital

b) the size and energy level of the orbital

c) the spatial orientation of the orbital along a coordinate axis

d) the spin of the electron

17. Which correctly describes the Pauli exclusion principle?

a) Pairs of electrons always have the same four quantum numbers.

b) Electrons can occupy the same space if they have identical

spins.

c) Electrons are confined to regular orbits around the nucleus.

d) No two electrons in an atom have the same four quantum

numbers.

18. Which is not a result of electron shielding?

a) orbital shapes

b) outer-shell electrons are held less tightly than inner-shell

electrons



c) the effective nuclear charge is lowered

d) all of the above

19. Which element’s ground state electron configuration does

[Kr] 5s24d5 describe?

a) Fe

b) Mn

c) Tc

d) Mo

20. Which best describes an electron orbital?

a) a well-defined path that the electron takes when it orbits the

nucleus

b) a region of space where an electron is likely to be found

c) a region of space where electrons are always located

d) the USSR rocket that put the MIR space station in orbit

Chemistry 2031 Chemistry I Exam 2 Long

Problems (60 points)

Name ______________________



SSN ______________________

Directions: Show all work to receive partial

credit. Remember to include proper units and

the correct number of significant figures.

21) Use this unbalanced reaction to answer the following:

MnO4-(aq) + Cu( s) ==> MnO2( s) + Cu(OH)2( s)

a) Write the oxidation number (oxidation state) for each atom (8 points)

_+7_ _-2_ __0_ _+4_ _-2_ _+2 _-2_ _+1_

b) Write the balanced oxidation half-reaction. (5 points)

Cu(s) + 2H2O(l) ==> Cu(OH)2( s) + 2H+(aq)

c) Write the balanced reduction half-reaction. (5 points)

MnO4-(aq) + 4H+(aq) ==> MnO2( s) + 2H2O(l )

d) How many electrons are gained or lost by Mn in MnO4-(aq)? (2 points)

Mn gains 3 electrons



e) How many electrons are gained or lost by Cu( s)? (2 points)

Cu loses 2 electrons

f) What is the balanced equation for an acidic solution? Show your work. (10

points)

[Cu(s) + 2H2O(l) ==> Cu(OH)2( s) + 2H+(aq) ] 3

[MnO4-(aq) + 4H+(aq) ==> MnO2( s) + 2H2O(l )] 2

3Cu(s) + 6H2O(l) + 2MnO4-(aq) + 8H+(aq) ==>

3Cu(OH)2( s) + 6H+

(aq) + 2MnO2( s) +

4H2O(l )

cancel

3Cu(s) + 2H2O(l) + 2MnO4-(aq) + 2H+(aq) ==>

3Cu(OH

2MnO2

f) What is the balanced equation for a basic solution? (10 points)

Add OH- to neutralize the acid

3Cu(s) + 2H2O(l) + 2MnO4-(aq) + 2H+(aq) + 2OH-(aq) ==>



3

C

u

(O

H

)

2

(

s

)

+

2

M

n

O

2

(

s

)

+

2

O

H-

(

a



q

)

(H+ + OH- ==> H2O)

3Cu(s) + 4H2O(l) + 2MnO4-(aq) ==> 3Cu(OH)2( s) +

2MnO2( s) +2OH-(aq)

22. Sodium atoms emit light with a wavelength of 330 nm when an electron

moves from a 4p orbital to a 3s orbital. What is the energy difference between

the orbitals in kJ/mol? (8 points)

330 nm = 3.30 x 10-7 m

Ephoton= hc/l = (6.626 x 10-34 J*s)(3.000 x 108 m/s)/ 3.30 x 10-9 m = 6.02 x 10-19

J = 6.02 x 10-22 kJ

Emol photons = (6.02 x 10-22 kJ) (6.022 x 1023/mol) = 363 kJ/mol

23a. Give the expected ground state electron configuration for Sn. (5 points)

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p2

or [Kr] 5s2 4d10 5p2

b. Give the expected ground state electron configuration for Sn2+. (5 points)

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10



or [Kr] 5s2 4d10

Exam 2 Cheat Sheet

λ = c / ν

ν = c / λ

1/λ = R[1/m2 - 1/n2] R = 1.097 x10-2 nm-1

ν = R*c[1/m2

- 1/n2

] R = 1.097 x10-2

nm-1

E = h ν

E = hc/λ

m = h/λc

λ = h/m ν

(∆x)(∆m ν) > h/4π

solubility rules of thumb

1. A compound that contains one of the following cations is

probably soluble:

Group 1A cation: Li+, Na+, K +, Rb+, Cs+

Ammonium ion: NH4+

2. A compound that contains one of the following anions is

probably soluble:



Halide: Cl-, Br -, I-

except Ag + , Hg 22+ , & Pb2+ compounds

Nitrate (NO3-), perchlorate (ClO4

-), acetate (CH3CO2-), sulfate

(SO42-)

except Ba2+ , Hg 22+ , & Pb2+ sulfates

other compounds are probably insoluble:

alkaline earth or transition metal cations with OH -, O2-, CO32-, PO4

3-, CrO42-, or

S2- anions

ChemistryGoodInfo Chemistry I Exam 2

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