1045_practice_exam_1_f23 (1)

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Florida International University *

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1045

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Chemistry

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Dec 6, 2023

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FLORIDA INTERNATIONAL UNIVERSITY DEPARTMENT of CHEMISTRY AND BIOCHEMISTRY BISCAYNE BAY CAMPUS Name: _________________________________ CHM 1045 Panther ID: __________________________________ Fall First Exam Laboratory Instructor’s Name: _______________________ Practice exam Useful information 1 mol = 6.02 x10 23 atoms or entities °F = 1.8 °C + 32 K = °C + 273.15 h=6.626 x10 -34 Js c=3.00x10 8 m/s R H = 2.18x10 -18 J ν = c/λ  E = h ν = hc/λ  E = -R H (1/n f 2 – 1/n i 2 ) D = mass/volume (g/mL)

1. What is the state of matter represented for water in the picture from first day of semester? a. solid b. gas c. liquid d. plasma 2. During the first day of the semester we study the states of matter and energy requirements for phase changes. Identify the state and energy requirement for the process shown below from left to right. a. the transition shown above is from solid to liquid and requires energy for it to occur b. the transition shown above is from liquid to gas and releases energy in the process c. the transition shown above is from solid to liquid and releases energy for it to occur d. the transition shown above is from solid to gas and releases energy in the process e. the transition shown above is from liquid to solid and releases energy in the process 3. How many hydrogen atoms are in 2.50 g of pharmacolite, CaHAsO4•2H 2 O (MMass = 216.0 g/mol)? a. 6.97 × 10 21 atoms of H b. 2.09 × 10 22 atoms of H c. 2.79 × 10 22 atoms of H d. 3.48 × 10 22 atoms of H e. 4.18 x 10 22 atoms of H 4. Paying attention to units can avoid disasters such as the Mars orbiter destruction in 1999. Two teams of scientists across the Atlantic worked in two different sets of units, metric and English resulting in a sad time in the quest for Mars exploration. To start, to escap e Earth’s orbit a space vehicle must reach a velocity beyond 25,000 mi/hr or it will remain orbiting the Earth. What would the escape velocity be in Km/sec? 1km = 0.62137 mi. a. 11.176 km/sec b. 12.345 km/sec c. 670.6 km/sec d. 4.315 km/sec 5. To reach the escape velocity and beyond the rover needs a solid propellant. To my surprise the solid propellant most commonly used is ammonium perchlorate, NH 4 ClO 4 in a binding material. 2,020 kg of solid propellant is used in one rocket that burns for 90 seconds. Have you wondered how many oxygen atoms are present in that sample? Molar mass NH 4 ClO 4 = 117.49 g/mol. a. 1.035 x 10 28 atoms O b. 4.866 x 10 30 atoms O c. 4.141 x 10 28 atoms O d. 1.035 x 10 25 atoms O e. 4.141 x 10 25 atoms O

6. Aluminum is frequently used to build electronics due to its low cost and low weight. The molar mass of aluminum according to the periodic table is 26.97 g/mol; a small car has a mass of 1200. Kg. How many moles of aluminum have a mass equal to the mass of a small car? a. 3.236 x 10 7 moles Al b. 1.85.4 x 10 5 moles Al c. 4.449 x 10 4 moles Al d. 44.49 moles Al 7. Learning about the periodic table allows us to make predictions on properties of elements and their behavior. Select the correct statement with the correct reason from the statements listed below: I. Based on photoelectric effect, it is easier to remove electrons from a surface of calcium than for sodium. II. The IR region of the electromagnetic spectrum will have longer wavelength than the UV region of the spectrum. III. the transition n=6 to n=1 will require more energy than the transition from n=6 to n=2 Reasons: IV. Calcium is larger than sodium and easier to eject electrons from its surface. V. n=6 to n=1 energy levels are farther away requiring more energy for the jump of the electron. VI. Calcium outer electrons are in 4s 2 making it easier to remove. VII. IR is a weaker radiation than UV and therefore has lower frequency than UV resulting in longer wavelength. VIII. the transition from n=6 to n=2 will require more energy than the other one. IX. IR is a stronger radiation than UV and therefore has lower frequency than UV resulting in longer wavelength. a. III and V b. II and VII c. II and IX d. I and IV e. I and VI 8. Scientists returning to Earth from the Space lab report analysis for two new elements. Do you agree or disagree with the scientists and should we all celebrate the formation of two new elements? I. Element 1 has 116 electrons, 116 protons and 190 neutrons II. Element 2: has 120 electrons, 120 protons and 190 neutrons. a. We can celebrate the formation of one new element as both of those descriptions are isotopes of the same element as the number of neutrons are the same. b. some celebration is in order as element 2 is a new element but element one already exists c. major celebration as these are two new elements, the number of protons is different; wondering what their names will be. d. there should not be a celebration because there are no new elements here. They already exist as they are isotopes of an existing element. 9. Select the element that has the highest level of paramagnetism. a. As b. Ca c. Br d. Tc e. Rb 10. What element is represented by the electronic configuration: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 4 . a. Se b. Br c. S d. Te e. not listed 11. LED bulbs are advertised as good replacement to incandescent lights. Typical LED lights used in homes are 8.5 Watts versus 60 Watts for typical incandescent light bulbs. Watt is a unit of power equivalent to 1 joule of work per second. 1 Watt = 1 J/sec. These LED lights do not emit white light which would be a combination of all wavelengths in the visible range. LED lights emit in the blue region at 483 nm and it is the yellow coating of the bulbs that makes it look white. What is the energy of a single photon associated with the LED lightbulb? a. 7.82 x 10 -19 J b. 4.12 x 10 -19 J

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