CP Chemistry Semester 1 Final Review KEY

Unit 1 Practice Problems

1. What tool do you use to measure volume of water? Describe how to make a proper measurement of a volume of water using a 50 mL graduated cylinder (each line = 1 mL) with correct significant figures.

Graduated cylinder. You should have 1 estimated digit (1/10th of a ml) 2. Complete the following conversions:

a. 4542m Km 4.542 Km b. 0.00987 L mL 9.87 mL c. 432 cm inches (1inch = 2.54cm) 170 in d. 5819876543 feet inches 6.98x1010 in e. 65 dL L 6.5 L f. 9824mg g 9.824g g. 657 kg g 657000g

3. What are the metric units for length, volume, and mass? Length-meter Volume-liter mass-gram 4. What is the volume of water in this graduated cylinder (using

correct sig. figs.)? How many significant figures do you have? (graduated cylinder looks different on your printout—answer is for the one on your handout, not this one) 20.4 ml, 3 sig figs. 5. Write 4653000 and 0.000547228 in scientific notation. How many significant figures

are in each number? 4.653 x 106 (4 sig. figs), 5.47228 x 10-4 (6 sig. figs) 6. Write 6.981 x 104 and 3.2231 x 10-3 in standard notation. How many significant

figures are in each? 69810 (4 sig. figs), 0.0032231 (5 sig. figs) 7. Given a ruler with graduations in 0.1 cm (each line = 0.1 cm), why would it be

incorrect for a student to record the length of a paper clip as 4.5011cm? You can only have 1 estimated digit, which would be 1/10th of the smallest graduation (in this case, the hundredths place). Measuring with correct significant figures indicates the level of uncertainty of a measurement. 8. A student determined the density of an unknown metal to be 4.58g/ml. The actual

density is 4.36g/ml. What is the student’s percent error?

!"#$"%&!!""#" = !4.58!/!" − 4.36!/!"4.36!/!" ×100 = 5.04%

9. If you consistently hit 8inches to the left of the bulls eye, are you accurate, precise, both, or neither?

Precise (all close together) but not accurate (didn’t hit bulls eye)

10. Complete the following operations and round with correct significant figures. a. 0.81 + 0.9 + 1.11 =2.8 b. 4.53 x 10.0 =45.3 c. 879/23 =38

d. !".!!!!".!!.! =6.9 11. You have 1.67 mole of carbon tetrahydride. How many molecules of carbon

tetrahydride do you have?

1.67!!"#!!"!!× !6.022!×10!"!!"#$%&#$'

1!!"#!!"!= 1.01!×10!"

12. 12.0 g of CO2 has a volume of 6.11 L.

a. What is the density of CO2? !"#$%&' = ! !".!!!.!!!! = 1.96!/! b. What is the molar mass of CO2? 12.01 + 2x16.00 = 44.01 g/mol c. How many moles of CO2?

12.0!!!"!×1!!"#!!"!44.01! = 0.273!!"#!!"!

d. How many molecules of CO2?

12.0!!!"!×1!!"#!!"!44.01!!!!"!

× 6.022!×10!"!!"#$%&#$'!!"!

1!!"#!!"!= 1.64!×10!"!!"#$%&#$'!!"!

13. A balloon contains 0.456g of He. How many moles of He are in the balloon? Atoms?

0.456!!!"× 1!!"#!!"4.00!!!!" = 0.114!!"#!!"

0.456!!!"× 1!!"#!!"4.00!!!!"×

6.022!×10!"!!"#$%!!"1!!"#!!" = 6.87!×10!!!!"#$%!!"

14. What is matter? What 2 properties does all matter have?

Matter has mass and takes up space (volume). 15. A substance has a definite volume but an indefinite shape. What state of matter is it?

liquid 16. How would you find the density of an irregularly shaped object? Find mass using a balance. Partially fill graduated cylinder with water and record volume as Vinitial. Put object in water—water level will rise due to displacement and record new volume as Vfinal. !"#$%&' = !"##

!!"#$%!!!"!#!$%

17. What is the density of an object with a mass of 540g and a volume of 368 mL?

!"#$%&' = ! 540!368!!" = 1.47 !!"

18. Distillation separates a mixture based on what property? Boiling point 19. Is density a physical or chemical property? Intensive or extensive? Physical,

intensive 20. What kind of property is boiling point? What kind of change is boiling? Boiling point

is a physical property, and boiling is a physical change. 21. Classify the following as a purse substance (element compound) or mixture

(homogeneous or heterogeneous).

a. Air mixture, homogeneous b. Cereal mixture, heterogeneous c. Steel mixture, homogeneous d. Gold pure substance, element e. Water pure substance, compound f. sand mixture, heterogeneous

22. How many protons, neutrons, and electrons does a sodium-23 cation have? 11 protons, 12 protons (23-11 = 12), 10 electrons (cation has lost one electron) 23. Give the nuclear notation for the most common isotope of Carbon. !!!"

24. Elemental sodium (Na) reacts violently with water. Is this a physical or chemical

property? Chemical property

25. Identify the scientists: a. elements made of indestructible, identical atoms that combine to make

compounds Dalton b. identified cathode rays as electrons and measured charge-to-mass ratio

Thomson c. measured electron charge with oil drops in a vacuum chamber Milikan d. characterized nucleus as dense and positive with gold foil and alpha (a)

radiation Rutherford e. characterized electron region in terms of energy levels and concentric "orbits"

Bohr 26. What are the 3 subatomic particles? What are their relative charges and mass? Protons:+1, ~1 amu Neutron: no charge, ~1 amu Electron: -1, very small mass (1/2000 mass of a proton) 27. Write the nuclear notation for an atom where Z=34 and N=45. !"!"

!"

28. Copper has two naturally occurring isotopes. Copper-63 has an abundance of 69.15% and a mass of 62.9296 amu. What is the atomic mass of the second isotope?

100%-69.15%=30.85% (abundance of second isotope) (.6915)(62.9296amu) + (.3085)(X) = 63.55 amu (this number comes from the periodic table) X=64.94amu (mass of second isotope)

29. Give the nuclear notation for Copper-63 and Iodine-127.

!"!"!" !!"

!"#

Unit 2: Practice Problems:

1. What are the symbols for frequency and wavelength? What are the units for frequency, wavelength, and wave speed for EM radiation?

Frequency: v, /s or Hz Wavelength: λ, nm or m (need to use m if plugging into equations!) Wave speed: m/s 2. What is the energy of EM radiation with a wavelength of 700nm?

700!"!× 1!!1×10!!" = 7!×10!!!

! = ℎ!! = 6.626×10!!"! ∗ ! (3.00!×10!!/!)

7×10!!! = 2.84×10!!"!

3. What is the frequency of EM radiation with a wavelength of 610nm?

610!"!× 1!!1×10!!" = 6.10!×10!!!

! = ℎ!!!!!!!!!!!! = !ℎ =

3.00!×10!!/!6.10!×10!!! = 4.92×10!"!"

4. In the visible spectrum, which color light has the most energy? The longest

wavelength? Violet light has the most energy (ROYGBIV). Red has the longest wavelength. 5. If you look at a neon sign using a spectroscope, will you see a continuous or

emission spectra? Emission spectra!

6. What is the frequency of a photon that has 6.8 x 10-19 J of energy?

! = ℎ!!!!!!!! = !ℎ = !

6.8×10!!"!6.626×10!!"! ∗ ! = 1.03×10!"!"!!"!/!

7. When an atom is excited, has it gained or lost energy? Absorb or emit a photon? Atom has gained energy, absorbed a photon. 8. Compared to green light, yellow light has more/less energy, a longer/shorter

wavelength, and a higher/lower frequency. Less E, longer λ, lower v ROYGBIV More E, shorter λ, higher v

9. In an hydrogen atom, an electron transitions from n=4 to n=2. Did the electron gain or lose energy? Did it absorb or emit a photon?

The electron lost energy and emitted a photon 10. What is the energy of an electron at n=4? Calculate ΔE when the electron transitions

from n=1 to n=4?

! = −2.18!!!10−18!!2 =

−2.18!!!10−18!42 = −1.36×10−19!

! = −2.18!!!10−18!!2 =

−2.18!!!10−18!12 = −2.18×10−18!

∆! = !!"#$% − !!"!#!$% = −1.36×10!!"! − −2.18×10!!"! = !!.!"!!×!"!!"!

11. How do we know that the energy levels in a hydrogen atom are not continuous? Hydrogen does not emit light of all wavelength—emits only certain wavelengths of light that correspond to transitions between different energy levels. 12. Complete the chart

Energy Level

# of orbitals

(n2)

orbital letters

# of orbitals in each type

total # of e- (2n2)

1 1 s s-1 2 2 4 s,p s-1, p-3 8 3 9 s,p,d s-1, p-3, d-5 18 4 16 s,p,d,f s-1, p-3, d-5, f-7 32

13. Draw a Bohr model of a hydrogen atom showing an electron transitioning from n=3 to n=5. Show the photon and then calculate ΔE.

Electron should start at n=3 (closer to nucleus) and end at n=5 (farther from nucleus). Photon should be absorbed by the electron.

! = −2.18!!!10−18!!2 =

−2.18!!!10−18!52 = −8.72×10−20!

! = −2.18!!!10−18!!2 =

−2.18!!!10−18!32 = −2.42×10−19!

∆! = !!"#$% − !!"!#!$% = −8.72×10!!"! − −2.42×10!!"! = !!.!!!×!"!!"!

14. When filling a p orbital, why do you separate the electrons into different orbitals

before pairing them up? What is the name of this rule? Lower energy, Hund’s rule 15. Identify the elements based on their configurations:

a. [Ar]4s23d2 (sorry typo on your review) Titanium b. 1s22s22p63s1 Sodium c. [Ne]3s23p5 Chlorine d. [Ar]4s13d10(sorry typo on your review) Copper

16. How many valence electrons do the elements in group 2 have? Group 14? Group 2 elements have 2 valence electrons, group 14 elements have 4 valence electrons. 17. What does it mean that an atom is in the ground state? Its electron configuration is

in the lowest energy state. The configuration is what is predicted by the periodic table.

18. How does Bohr's "electron orbits" differ from the "electron orbitals"? Electron

orbitals are three dimensional spaces where the electrons are likely to be found. Bohr’s electron orbits are concentric circles where the electron is confined to a planet like orbit.

19. What do elements in the same group have in common? Same chemical properties, same number of valence electrons.

20. What do elements in the same period have in common? Valence electrons in the same principle energy level.

21. Draw the electron dot diagram, and electron configuration for the following elements.

Symbol Electron-dot diagram

Electron configuration (use noble gas shortcut)

Ne

[He]2s22p6

Cu !"

[Ar]4s13d10

S2-

[Ne]3s23p6

Pu

[Rn]7s25f6

Ca2+ [Ne]3s23p6