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CHEM 110 โ Dr. McCorkle โ Exam #4 KEY
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calculators, or sharing calculators. Grade corrections for incorrectly marked or
incompletely erased answers will not be made.
- How many valence electrons do the halogens possess? A) 1 B) 2 C) 5 D) 6 E) 7
- Suppose a metal ejects electrons from its surface when struck by red light. What will happen if the surface is struck by blue light? A) No electrons would be ejected. B) Electrons would be ejected, and they would have the same kinetic energy as those ejected by red light. C) Electrons would be ejected, and they would have greater kinetic energy than those ejected by red light. D) Electrons would be ejected, and they would have lower kinetic energy than those ejected by red light.
- Identify the isoelectronic elements A) Clโ, Fโ, Brโ, Iโ, Atโ B) N3โ, S2โ, Brโ, Cs+, Sr2+ C) P3โ, S2โ, Clโ, K+, Ca2+ D) Zn2+, Co2+, Cu2+, Cr2+, Cd2+ E) Ne, Ar, Kr, Xe, He
- What period 3 element has the following ionization energies (all in kJ/mol)? IE 1 = 1012 IE 2 = 1900 IE 3 = 2910 IE 4 = 4960 IE 5 = 6270 IE 6 = 22,
A) Mg B) Si C) P D) S E) Cl
- Arrange the elements in order of increasing IE 1 : N, F, As A) N < As < F B) As < N < F C) F < N < As D) As < F < N E) F < As < N
- Arrange the elements in order of increasing metallic character: P, As, K A) P < As < K B) As < P < K C) K < P < As D) As < K < P E) K < As < P
Calculations โ Write your initials in the upper-right corner of every page that contains work. For full credit show all work and write neatly; give answers with correct significant figures and units. For calculations, place a box around your final answer.
- For the following short answer questions, please circle, fill-in, or provide the correct answer. [2 points each]
a. Which transition has a longer wavelength? n = 7 โ n = 5 n = 3 โ n = 1
b. Which has the lowest energy? 6 s 5 d 4 f
c. A gas phase element gaining an electron is a typically endothermic process. True False
d. How many electrons in an atom could have n = 4, l = 2 , ml = +1? ____ 2 _____
e. The two most probable ions of titanium are ___ Ti2+ ____ and ___ Ti4+ ____.
- How many photons are contained in a flash of green light (525 nm) that contains 189 kJ of energy? [4 points]
๐๐๐ ๐ง๐ฆ ร
๐๐โ๐^ ๐ฆ
= ๐. ๐๐ ร ๐๐โ๐^ ๐ฆ
(๐. ๐๐๐ ร ๐๐โ๐๐^ ๐ โ ๐ฌ)(๐. ๐๐๐๐ ร ๐๐๐^ ๐ฆ/๐ฌ)
๐. ๐๐ ร ๐๐โ๐^ ๐ฆ
= ๐. ๐๐ ร ๐๐โ๐๐^ ๐/๐ฉ๐ก๐จ๐ญ๐จ๐ง
๐๐๐ ๐ค๐ ร
๐๐๐^ ๐
= ๐. ๐๐ ร ๐๐๐^ ๐
๐. ๐๐ ร ๐๐๐^ ๐
๐. ๐๐ ร ๐๐โ๐๐^ ๐/๐ฉ๐ก๐จ๐ญ๐จ๐ง
= ๐. ๐๐ ร ๐๐๐๐^ ๐ฉ๐ก๐จ๐ญ๐จ๐ง๐ฌ
- Calculate the de Broglie wavelength in meters of a 46 g golf ball with a velocity of 30. m/s. [3 points]
๐ฆ = ๐๐ ๐ ร ๐ ๐ค๐ ๐๐๐^ ๐ = ๐. ๐๐๐ ๐ค๐
๐ = ๐ฆ๐ฏ๐ก = ๐.๐๐๐ร๐๐
โ๐๐ (^) ๐โ๐ฌ (๐.๐๐๐ ๐ค๐ )(๐๐. ๐ฆ/๐ฌ) = ๐. ๐ ร ๐๐
- Explain the trends in atomic radius across a period (from left to right) and down a group (from top to bottom). [4 points]
Atomic radius decreases across a period because electrons are being added
to the same valence shell but the effective nuclear charge increases as
protons are added to the nucleus, causing increased attraction with the
electrons, pulling them closer, decreasing the radius.
Atomic radius increases down a group because electrons are being added
to higher energy shells that are farther away from the nucleus.
- Consider the electronic transition within a hydrogen atom from n = 5 to n = 2.
a. Calculate the energy of the photon that is emitted in joules. [2 points]
๐๐ฉ๐ก๐จ๐ญ๐จ๐ง = ๐๐ฏ [( ๐ง๐
๐๐ข๐ง๐๐ฅ๐^
๐ข๐ง๐ข๐ญ๐ข๐๐ฅ๐^
)]
๐๐ฉ๐ก๐จ๐ญ๐จ๐ง = ๐. ๐๐ ร ๐๐โ๐๐^ ๐ [(
)] = ๐. ๐๐ ร ๐๐โ๐๐^ ๐
b. Calculate the frequency in Hertz. [2 points]
E = hฮฝ
๐. ๐๐ ร ๐๐โ๐๐^ ๐
๐. ๐๐๐ ร ๐๐โ๐๐^ ๐ โ ๐ฌ
= ๐. ๐๐ ร ๐๐๐๐^ ๐๐ณ
c. Calculate the wavelength in meters. [2 points]
E photon = ๐ก๐๐
(๐. ๐๐๐ ร ๐๐โ๐๐^ ๐ โ ๐ฌ)(๐. ๐๐๐๐ ร ๐๐๐^ ๐ฆ/๐ฌ)
๐. ๐๐ ร ๐๐โ๐๐^ ๐
= ๐. ๐๐ ร ๐๐โ๐^ ๐ฆ
d. Does this emission occur within the visible region of the electromagnetic spectrum? [ points]
๐. ๐๐ ร ๐๐โ๐^ ๐ฆ ร
๐ ๐ง๐ฆ
๐๐โ๐^ ๐ฆ = ๐๐๐ ๐ง๐ฆ^ Yes, this is visible (indigo).
Formulas & Constants (you may or may not need)
1 inch = 2.54 cm (exact) 1 mile = 5280 ft โ 1.609 km 1 kg โ 2.205 lb
1 lb = 16 oz โ 453.6 g 1 gal = 4 qt = 8 pt โ 3.785 L 1 L = 1000 cm^3
K = ๏ฐC + 273.15 ๏ฐF = 1.8 x ๏ฐC + 32 ๏ฐC = (๏ฐF โ 32)/1.
1 cal = 4.184 J 1 Cal = 1000 cal q = m x C x ฮT
Avogadroโs # = 6.022x10^23 Molar volume = 22.4 L R = 0.08206 LโatmmolโK
P 1 V 1 T 1 =^
P 2 V 2 T 2 ๐ขrms^ = โ
3RT ๐ ๐พ๐ธ =^
1 2 ๐๐ฃ
(^2) = 3 2 ๐
๐
1 atm = 760 mmHg 1 mmHg = 1 torr PTotal = P 1 + P 2 + ...
PA = ฮงA ยท PTotal PV = nRT โE = q + w
w = โPโV q = C ร โT q = m ร s ร โT
โ H ยฐrxn = ฮฃ[n โ H fยฐ(products)] โ ฮฃ[n โ H fยฐ(reactants)] R = 8.314 J/mol ยท K
h = 6.626ร10โ^34 J ยท s c = 2.9979ร10^8 m/s RH = 2.18ร10โ^18 J
1 Hz = sโ^1 ฮป = (^) mvh โx ร mโv โฅ (^) 4ฯh
E photon = hฮฝ = hcฮป ๐ธphoton = R๐ป [( (^) n^1 final^2 ) โ ( (^) n^1 initial^2 )]
Scratch Page
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