Chemistry 1: Structure of Matter Name __________________________A. Measurement (1.4 to 1.6)

1. science knowledge is advanced by observing patterns (laws) and constructing explanations (theories), which are supported by repeatable experimental evidencea. theory lasts until disprovenb. theory is never 100 % certain

2. uncertainty in measurementsa. precision and accuracy

1. precise = consistent (even if incorrect)2. accurate = correct (even if inconsistent)

precise precise & accurate accurateb. data analysis

1. accuracy is measured by percent difference% = 100|mean – true|/true

2. precision is measured by percent deviation% = 100|trial – mean|/N(mean) (N is number of trials) absolute = |trail – mean| average = absolute )/N % = 100(average )/(mean)

c. significant figures (sf) indicate level of certainty

measurement includes all certain (numbered) plus one estimated value 7.5 cm (2 sf)

d. rules for counting significant figures 1. all nonzero digits are significant2. zero is sometimes significant, sometimes not

a. example: 0.00053000021000 never always ?

b. (?) decimal vs. no decimal1. significant with decimal: 120. (3 sf)2. not significant w/o decimal: 120 (2 sf)

3. exact numbers (metric conversions, counting or written numbers) have infinite number of sf

4. scientific notation: C x 10n a. C contains only significant figuresb. 1200 with 3 sf: 1.20 x 103

e. rules for rounding off calculations1. limited by least accurate measurement2. x, : answer has the same number of sf as

the measurement with the fewest3. +, –: answer has same end decimal position

as measurement with left most end position3. SI measuring system

a. summary chartMeasurement SI standards Chemistry

mass kilogram (kg) gram (g)volume cubic meter (m3) liter (L)

temperature kelvin (K) Celcius (oC)time second (s) varies

b. prefixes system (x 10X)1. k3, c-2, m-3, µ-6, n-9

2. squared/cubed prefix: 1 cm2 = 1 x (10-2)2 m2

3. 1 mL = 1 cm3

4. 455 kg x 10 3 g x (10 -2 ) 3 m 3 = 0.455 g m3 1 kg 1 cm3 cm3

4. mass and volume measure amount of mattera. density: d = m/V

1. units depend on units for m and V2. dH2O = 1.00 g/mL = 1.00 g/cm3 = 1000 kg/m3

b. number of particles: mole = 6.022 x 1023 particles1. periodic table mass equals formula mass in g 2. molar mass (MM)—sum of mass of atoms in

chemical formula (use 3 significant figures)a. Al: 27.0 g/molb. H2O: 18.0 g/mol

c. conversions (dimensional analysis)1. mass moles (given formula or MM)

__ g x 1 mole/(MM) g = __ mole2. volume mass (given density–d)

__ mL x (d) g/1 mL = __ g3. volume mass moles (given d and MM)

__ mL x (d) g/1 mL x 1 mole/(MM) g = __ moleB. Atomic Nature of Matter (2.1 to 2.7)

1. historical perspectivea. Dalton's atomic theory (1805)

1. unique, indestructible atoms for each element2. atoms are rearranging, not created during

chemical change3. compounds are groups of atoms in fixed ratio

b. subatomic structure1. J. J. Thomson (1897): identified cathode rays

as electrons, measure charge-to-mass ratio 2. Millikan (1909): measure electron charge

with oil drops in a vacuum chamber3. Rutherford (1910): characterized dense,

+ nucleus with alpha () radiation and gold foil 2. components of the atom

a. subatomic particlesParticle Location Charge Mass SymbolProton nucleus + 1 1.0 1

1p or 11H

Neutron nucleus 0 1.0 10n

Electron outside - 1 .00055 o-1e

b. atomic number (Z) 1. number of protons 2. defines type of atom

c. mass number (A)1. protons + neutrons2. isotopes (same Z, different A)3. nuclear symbol: A

ZXd. ions are atoms where # electrons # protons

1. e > p: (–) charged (anion): Xn-

2. e < p: (+) charged (cations): Xn+

e. unified atomic mass unit (u)1. 1 u = 1/12 the mass of a C-12 atom2. average atomic mass (periodic table mass)

a. isotopes have fixed % in natural sampleb. 100mav = %1m1 + %2m2 + ...

3. forms of mattera. pure substance has a unique

composition of atoms unique formula and set of properties1. elements—one type of atom

(diatomic: H2, N2, O2, F2, Cl2, Br2, I2)2. compounds—two or more types

of atomsa. molecular—formula

defines size

b. crystalline—formula shows ratio of atoms

b. mixture of pure substances in an object or container1. variable composition (no set formula)

2. uniform: homogenous mixture = solution

3. non-uniform: heterogeneousc. summary

Monatomic Molecular Molecular Homogeneous Element Element Compound Mixture

Crystalline CompoundC. Radioactivity (21.1 to 21.4)

1. forms of natural radiation

Type Symbol Mass # (A)

Charge # (Z)

Relative penetratio

nalpha 4

2He 4 +2 1beta 0

-1e 0 –1 100positro

n 01e 0 +1 destroye

dgamma 0

0 0 0 10,0002. balancing nuclear reactions using nuclear symbols: A

ZX balance A and Z values determine symbol by Z number 238

92U 42He + 234

90Th3. nuclear instability

a. isotopes that are outside the "belt of stability" tend to be radioactive

b. modes of decay1. atomic number > 83— (alpha)

22688Ra 222

86Rn + 42He

2. Aisotope > Aaverage: 10n 1

1p + 0-1 (beta)

146C 14

7N + 0-1e

3. Aisotope < Aaverage: 11p 1

0n + 01 (positron)

116C 11

5B + 01e

alpha decay

beta decay positron decay

4. transmutationsa. induced nuclear reactions by bombardmentb. 14

7N + 42He 17

8O + 11H

c. produce trans-uranium elements

5. radioactive decay

a. rate of decay number of radioactive atoms (Nt)1. rate = kNt (k: rate constant) 2. time for half of remaining atoms to decay (t½)

is constant: k = (ln2)/t½

b. ln(No/Nt) = kt or Nt = Noe-kt

1. No = original amount2. t and k must have same time units

D. Electron Structure—Bohr Model(6.3 to 6.4)1. atomic spectrum

a. colors emitted by energized atoms (unique for each element)

b. calculations: Ephoton = 2.00 x 10-25 J•m/

1. = wavelength (m)2. = frequency (s-1) = c/3. Ephoton = hf = hc/

hc = (6.63 x 10-34 J•s)(3.0 x 108 m/s) = 2.00 x 10-25 J•m2. Bohr model—atoms with one electron only

a. energy levels (n)1. Eelectron = -B/n2 2. for H: En = -2.18 x 10-18 J/n2

3. ground state (n = 1) electron has lowest (most negative) energy

4. excited state (n > 1), electron energy increases until ionized (E = 0 J)

5. Eelectron = En-final – En-initial

a. Eelectron > 0 when increasing nb. Eelectron < 0 when decreasing n

b. |Eelectron| = Ephoton

434 nm 486 nm 656 nm blue blue-green red

Experiments1. Density Lab—Measure the mass and volume of a solid,

liquid and gas, determine densities, and use the density to identify the substances.Solid: Add 5.0 mL (V1) water to a 10 mL graduated cylinder. Mass the cylinder + water (m1). Add solid. Record the volume to the nearest 0.1 mL (V2). Mass (m2).a. Record the collected data. Calculate the change in

mass (m) and change in volume (V) and density (d). m2 – m1 = m V2 – V1 = V d = m/V

b. Highlight the type of solid based on its density.Al Zn Pb

d = 2.7 g/mL d = 7.1 g/mL d = 11 g/mLc. Calculate the number of moles of solid.

Liquid: Mass a clean, dry 10 mL graduated cylinder (m1). Add 10.0 mL liquid to the cylinder. Mass cylinder + liquid (m2). d. Record the collected data. Calculate the change in

mass (m), change in volume (V) and density (d). m2 – m1 = m V d = m/V

10. mLe. Highlight the type of liquid based on its density.

C2H6O H2O C3H8O3

d = 0.79 g/mL d = 1.0 g/mL d = 1.1 g/mLf. Calculate the number of moles of liquid.

Gas: Add ½ scoop of baking soda (NaHCO3) to the flask and ½ fill the pipet with 6 M HCl (HANDLE WITH CARE). Stopper the flask and mass the assembly (m1). Fill the gas collecting bottle with water. Measure the volume of water (V1). Refill the bottle, cover the mouth and place it inverted in the trough. Insert the open tube into the gas collecting bottle. Add the HCl to the flask, one drop at a time, until the gas collecting bottle is nearly full. Mass the assembly (m2). Measure the volume of water remaining in the bottle (V2).g. Record the collected data. Calculate the change in

mass (m) and change in volume (V) and density (d). m1 – m2 = m V1 – V2 = V d = m/V

h. Highlight the type of gas based on its density.H2 O2 CO2

d = 8.4 x 10-5 g/mL d = 1.3 x 10-3 g/mL d = 2 x 10-3 g/mLi. Calculate the number of moles of gas.

2. Penny Isotope Lab— Use the average mass of 50 pennies to determine the percentages of heavy pennies and light pennies, and compare to the actual percentages. Count 50 pennies and mass the total.a. Record the mass and calculate the average.

b. Calculate the percentage of 2.5-g and 3.1-g penny.

Separate the pennies into pre-1982, 1982 and post-1982 piles. Mass each 1982 penny. c. Record the number of pennies in each group and the

percentage of pennies that are 3.1 g and 2.5 g.pre-1982 1982 post-1982

3.1 g 3.1 g 2.5 g 2.5 g

Total %: Total %:

d. Calculate the % difference between the actual % of 2.5 g penny (c) and the calculated % (b).

3. Radioactive Decay Lab—Construct a half-life graph.Calculate the number of radioactive atoms that remain after given periods of time, graph the data and compare the graph to a ½-life graph.a. Calculate the rate constant k given t½ = 2.77 minutes.

b. Calculate the number of radioactive atoms that remain after each minute (Nt = Noe-kt).

t 0 1 2 3 4 5 6 7 8 9 10Nt 100c. Graph Nt vs. t.

Nt

80604020

0 1 3 5 7 9 t (minutes)

d. The slope of the line represents the rate of decay. How does the rate of decay change with time?

4. Hydrogen Spectrum Lab—Use hydrogen spectrum data to determine the electron transition which generates each color.a. Calculate Ephoton for each wavelength. Express all

answers as with 3 sf x 10-19 J (E = 2.00 x 10-25 J•m/).4.10 x 10-7 m 4.34 x 10-7 m 4.86 x 10-7 m 6.56 x 10-7 m

b. Calculate En for each value of n. Express all answers with 3 sf x 10-19 J (En = -2.18 x 10-18 J/n2).

1 2 3 4 5 6

c. Calculate E for each transition listed below. Express all answers with 3 sf x 10-19 J (E = En-final – En-initial).

6 to 5 5 to 4 4 to 2

6 to 4 5 to 3 4 to 1

6 to 3 5 to 2 3 to 2

6 to 2 5 to 1 3 to 1

6 to 1 4 to 3 2 to 1

d. Match the results from (a) and (c) and record the transition that produced each spectral line.

4.10 x 10-7 m 4.34 x 10-7 m 4.86 x 10-7 m 6.56 x 10-7 m

e. Rank the colors from highest energy (1) to lowest energy (4)?red blue-green blue violet

Practice ProblemsA. Measurement

1. How many significant figures are there in?0.008090 mL 1300.40 atm 13400 m one liter

2. Express the answers to the correct number of sf.(3.016)(4.23)

0.003112.0 + 1.01 + 6

101.43. How much do you have when you double 12.28 g?

4. A student measures the mass of an object to be 12.045 g. The true mass is 12.000 g. What is the percent error?

5. Determine the % deviation for the following massings.Mass 48.307 g 49.886 g 50.911 g 49.524 g

mean

Average

%

6. Convert the following:

345 nm m

3640 cm2 m2

350 mL L

155 cm3 L

7. A student adds 7.76 g of pellets to a graduated cylinder containing 5.00 mL. The total volume of the pellets and water is 7.87 mL. What is the density of the pellets?

8. A student measure the mass of an empty graduated cylinder (10.076 g), then fills it with 10.0 mL of liquid. The total mass of cylinder and liquid is 18.799 g. What is the density?

9. Calculate the molar masses to 3 significant figures.NaCl H2O Cl2

(NH4)2SO4 C4H7NO4 CuSO4•5 H2O

10. Use dimensional analysis to determine the following a. aluminum (MM = 27.0 g/mol, d = 2.70 g/cm3)

2.48 g Al mol

5.00 cm3 Al g

155 cm3 Al mol

b. carbon dioxide (MM = 44.0 g/mol, d = 1.82 g/L)

85.0 g CO2 L

3.15 mol CO2 g

3.22 L CO2 mol

B. Atomic Nature of Matter

11. How did Rutherford show that atoms have a nucleus?

12. Below is a modern view of an isotope of a sulfur atom.

16 protons 16 neutrons 18 electrons

Write the nuclear symbol for this ionized isotope.

13. Complete the chart below.Symbol protons neutrons electrons

2713Al

4019K+

3115P3-

26 30 23

17 17 18

79 118 79

14. Calculate the average atomic mass of Si, which consists of three isotopes listed below.Isotope Si-28 Si-29 Si-30Atomic Mass 27.98 28.98 29.97

Abundance 92.20% 4.70% 3.10%

15. Chlorine is primarily two isotopes Cl-35 and Cl-36 and has an average atomic mass of 35.45 u. a. Which isotope is more abundant? Explain

b. Estimate the approximate abundances for the two isotopes, Cl-35 and Cl-36 without using your calculator.

16. Antimony has two isotopes: Sb-123 and Sb-121. Sb-121 has a mass of 120.9 u and an abundance of 57.25 %. Antimony has an average atomic mass of 121.75. a. What is the abundance of Sb-123?

b. What is the atomic mass of Sb-123?

17. Consider the following molecules. Based on the model below, write the unique formula and formula mass.

FormulaMass

18. Fill in the flow chart from the word bank (compound, element, heterogeneous, homogeneous, matter, pure substance, solution).

Is it uniform throughout?

No Yes

Does it have a variable composition?

No Yes

Can it be separated into simpler

substances?No Yes

19. How is a molecular compound different from a non-molecular compound?

C. Radioactivity20. Write nuclear equation for the radioactive process.

Alpha emission of Ra-226

Beta emission of I-131

Positron emission of C-11

Th-231 decays to Pa-231

Th-232 decays to Ra-228

21. What is the most likely mode of decay for the isotopes?H-3 N-11 Co-60 Rn-222

22. Write a nuclear equation for the most likely mode of decay.

B-8

K-40

U-235

Co-60

23. Fill in the missing part of the nuclear transmutations.

_____ + 10n 24

11Na + 42He

147N + _____ 17

8O + 11H

168O + 1

1H _____ + 42He

5826Fe + 1

0n 5927Co + _____

24. Pu-239 undergoes nuclear fission when bombarded by a neutron. Determine the missing (?) product.

25. The graph shown below illustrates the decay of 8842Mo,

which decays via positron emission.

a. Write a nuclear equation for the decay of 8842Mo.

b. What is the half-life of the decay?

c. What is the rate constant for the decay?

d. What percent of the original sample remains after 12 minutes?

e. How many minutes does it take the sample to go from 0.8 g to 0.5 g?

26. The half-life of radioactive S-35 is 88 days. Determinea. the rate constant.

b. the number of days for the sample to be ¼ as radioactive (without a calculator).

c. the number of days for the sample to be ¼ as radioactive (with a calculator).

d. the percent that remain radioactive after 290 day.

27. C-14 (t½ = 5715 yrs) decays to N-14. As a result, the 14C/12C ratio in organic material decreases upon death. a. What is the rate constant k for C-14?

b. How old is an organic artifact whose 14C/12C ratio is 65.4 % of a living plant?

28. 238U (t½ = 4.5 x 109 yr) naturally decays to 206Pb. a. What is the rate constant k for U-238?

b. What is the age of the rock whose 206Pb/238U is 1.32/1?

D. Electron Structure—Bohr Model

29. Calculate the missing value.Photon energy Wavelength3.25 x 10-18 J

1.216 x 10-7 m6.60 x 10-19 J

345 nm30. A hydrogen electron transitions from n = 1 to n = 4.

a. What is the electron's energy at n = 1?

b. What is the electron's energy at n = 4?

c. Does the electron gain or lose energy in the transition?

d. What is the change in energy of the electron?

31. A hydrogen electron transitions from n = 9 to n = 7.a. What is the energy of the electron when n = 9.

b. What is the energy of the electron when n = 7

c. What is the change in energy for the transition?

d. Is energy absorbed or released during the transition?

e. What is the wavelength of the light emission?

Practice Multiple ChoiceBriefly explain why the answer is correct in the space provided.1. Based on the data, the density of the solid in g/mL is

Mass of metal 19.611 gVolume of water 12.4 mLVolume of water + metal 14.9 mL

(A) 7.8444 (B) 7.844 (C) 7.84 (D) 7.8

2. Which scientist is correctly matched with the discovery? (A) Millikan discovered the electron charge-to-mass ratio.(B) Thomson discovered the charge of an electron.(C) Bohr discovered the four quantum numbers.(D) Rutherford discovered the nucleus.

3. Which represents a pair of isotopes? (A) 14

6C and 147N (B) 18

9F and 3517Cl

(C) 5626Fe2+ and 56

26Fe3+ (D) 3517Cl and 36

17Cl

4. Copper has two isotopes, 63Cu and 65Cu. What is the abundance of 63Cu if the average atomic mass is 63.5?(A) 90% (B) 75% (C) 50% (D) 20%

5. Which of the following is correct about beta particles? I. mass number of 4 and a charge of +2

II. more penetrating than alpha particles III. electron

(A) I only (B) III only (C) I and II (D) II and III

6. For the types of radiation given, which is the correct order of increasing ability to penetrate a piece of lead?(A) < < (B) < < (C) < < (D) < <

7. 24996Cm is radioactive and decays by the loss of one beta

particle. The other product is (A) 245

94Pu (B) 24997Bk (C) 248

96Cm (D) 25096Cm

8. 25198Cf 2 1

0n + 13154Xe + . . .

What is the missing product in the nuclear reaction?(A) 118

42Mo (B) 11844Ru (C) 120

42Mo (D) 12044Ru

9. The radioactive decay of C-14 to N-14 occurs by (A) beta particle emission (B) alpha particle emission(C) positron emission (D) electron capture

10. What is the resulting nucleus after 21484Po emits 2 and 2

particles?(A) 206

83Bi (B) 21083Bi (C) 206

82Pb (D) 20882Pb

11. 23592U + 1

0n 14155Cs + 3 1

0n + XNeutron bombardment of uranium can induce the reaction represented above. Nuclide X is which of the following? (A) 92

35Br (B) 9435Br (C) 91

37Rb (D) 9237Rb

12. If 87.5 % of a sample of pure Pb-210 decays in 36 days, what is the half-life of Pb-210? (A) 6 days (B) 8 days (C) 12 days (D) 14 days

13. The half-life of isotope Y is 12 minutes. What mass of Y was originally present if 1 g is left after 60 minutes?(A) 8 g (B) 16 g (C) 24 g (D) 32 g

Practice Free Response1. You have a butane lighter for the purpose of measuring

butane's density at room temperature and pressure. a. How would you collect a sample of butane?

b. How would you determine the volume collected?

c. How would you determine the mass collected?

d. How would you determine the density of butane?

2. Consider the gas, UF6, which has a density of 15.7 g/L. a. What is the molar mass of UF6?

b. How many moles of UF6 have a volume of 1.00 L?

c. What is the volume of 25.0 g of UF6?

3. Write a brief description of the scientists' contribution.Scientist Contribution

J. J. Thomson

Millikan

Rutherford

Bohr

4. Write the symbol for an atom that contains 24 protons, 28 neutrons and 21 electrons.

5. Consider two variations of 2311

Na; 2411Na and 23

11Na+. How is each different from Na-23 and what is it called?

How is it different? Label isotope or ion24

11Na

2311Na+

6. Calculate the average atomic mass of Pb given the atomic masses and abundances of its stable isotopes.

Isotope Pb-204 Pb-206 Pb-207 Pb-208Atomic Mass 204 u 206 u 207 u 208 uAbundance 1.4% 24.1% 22.1% 52.4%

7. Consider the isotopes of copper.a. Write the beta decay of Cu-64.

b. When Cu-64 is bombarded with C-12, three neutrons and another particle are produced. Write the equation.

c. A sample of copper has two isotopes, Cu-63 and Cu-65. What is the % Cu-65 if the average mass is 63.5?

8. Determine the molar mass of the following pure substances.NaCl O2 C6H12O6 NH3

9. Place the forms of H (H, H+, H-, H2) in the table.Atom Cation Anion Molecule

10. Predict the mode of decay for the following nuclei and then write a balanced nuclear equation for the process.Nuclei Decay Mode Balanced Nuclear Equation

N-13

Cu-68

Np-241

11. Complete and balance the following nuclear equations. 32

16S + 10n 1

1H + _____

74Be + 0

-1e _____

_____ 18776Os + 0

-1e

23592U + 1

0n 13554Xe + 2 1

0n + _____

12. The half-life of Cr-51 is 27.8 days.a. Calculate the rate constant of Cr-51.

b. What percent of the sample will remain after 100 days?

13. The half-life of Y is 30 s. What mass of Y was originally present if 1 g is left after 60 s?

14. How old is a wooden artifact, which has a C-14 (t½ = 5715 yr) activity of 10.4 counts/min•g compared to living wood that has a C-14 activity of 13.6 counts/min•g?

15. Hydrogen atoms in the ground state are ionized by UV light. a. Calculate the energy needed to ionize an electron from

n = 1? (En = -2.18 x 10-18/n2 J).

b. Calculate the wavelength of UV light. (Ephoton = (2.00 x 10-25 J•m)/)

16. Answer the following questions regarding light and its interactions with molecules, atoms, and ions. a. The longest wavelength of light with enough energy to

break the CI-CI bond in CI2(g) is 495 nm. (1) Calculate the frequency in s-1 of the light.

(2) Calculate the energy in J of a photon of the light.

(3) Calculate the energy in kJ•mol-1 of the CI-CI bond.

b. A certain line in the spectrum of atomic hydrogen is associated with the electronic transition in the H atom from the sixth energy level (n = 6) to the second energy level (n = 2). (1) Indicate whether the H atom emits energy or

whether it absorbs energy during the transition. Justify your answer.

(2) Calculate the wavelength in nm of the radiation associated with the spectral line.