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Chem121–SU12PracticeforExam2
Question 1: How many electrons are associated with a double bond? _____4____________ Question 2: Which one of the following statements is generally true about electronegativity when you look at the periodic table? Circle one: a) Electronegativity decreases as we move left to right and decreases as we move top to bottom. b) Electronegativity decreases as we move left to right and increases as we move top to bottom. c) Electronegativity increases as we move left to right and decreases as we move top to bottom. d) Electronegativity increases as we move left to right and increases as we move top to bottom. Question 3: Circle the state of matter that has the weakest attractive forces between molecules: Solid Liquid Gas Question 4: Circle any of the following molecules that cannot engage in hydrogen bonding: a. CH4 c. H2O
b. NH3 d. Cl2 Question 5: According to the law of conservation of mass, which of the following may NEVER occur as a result of a chemical reaction? a. creation of new chemical species b. reaction of starting materials c. atoms rearranged to form new substances
d. reduction in total mass
Chem121–SU12PracticeforExam2
Question 7: Fill in the blanks of the statements below with the words in the box. Note, you will only use each word once. A. atom 1. A positively charged ion is a(n) ____cation________________. B. chemical symbol C. repel 2. A proton has a +1 ______charge_________________________. D. molar mass E. atomic number 3. Like charges ____repel_____________________ each other. F. protons G. isotopes H. charge I. cation J. neutrons 4. The ______molar mass______________________ of an element has the units g/mole. 5. Smallest unit of an element is a(n) ____atom_____________________________. 6. The ___chemical symbol_________ of an element is one or two letters found on the periodic table. 7. Isotopes have the same number of __protons_____ and different numbers of __neutrons_______. 8. Every element has a different _atomic number___________ and it equals the number of protons. 9. The atomic mass of an element is a weighted average of all the masses of all the naturally occurring __isotopes________ and has units amu. Question 8: Water 1. The molecular formula of water is ____H2O_____________________________. 2. Which element in water is the most electronegative? ______O______________. 3. Are all of the bonds in water polar?_____Yes_________________________. 4. Does water dissolve polar or non‐polar substances?____polar_____________________. 5. How many lone pairs of electrons are on the central atom of water? _2 pairs_____________. 6. Draw the Lewis Structure of water: O
H
H Question 9: Sucrose, C12H22O11 A. What is the correct ratio of Carbon atoms to Oxygen atoms in Sucrose? 12:11 Chem121–SU12PracticeforExam2
B. How many moles of sucrose are in 25.6 grams of sucrose? MW sucrose = 12*(12.01g/mole) + 22*(1.008g/mole) + 11*(16.00g/mole) = 342.30 g/mole 25.6 342.30
0.0748
C. The combustion of sucrose is an exothermic process. Balance the combustion reaction of sucrose below and add energy to the correct side of the equation: C12H22O11 + 12 O2  12 CO2 + 11 H2O + energy Question 10 How many calories are there in 3.76 joules? a. 0.899 calories b. 1.11 calories c. 15.7 calories d. 90 calories e. 1.6 x 105 calories Question 11. A. A sample of Freon gas in an air conditioner has a volume of 325 L and pressure of 96,300 Pa at O
20 C. What will the pressure of Freon be when the volume is 975 L at 20OC? 96300
325
20 273
975
20 273
P2 = 32100 Pa Chem121–SU12PracticeforExam2
B. The volume of 350.0 mL of gas at 25.0OC is decreased to 125 mL at constant pressure. What is the final temperature of the gas? 350.0
25.0 273
125
T2 = 106 K = ‐167 oC Question 12: What is the correct IUPAC name for a compound with the formula N2O3? Dinitrogen trioxide ‐
Question 13: The correct formula of an ionic compound containing Fe2+ and ClO4 is: Fe(ClO4)2 Question 14: The correct IUPAC name for the compound in question 13 is: Iron(II)perchlorate Question 15: Balance the reaction 2 Al(OH)3 + 3 H2SO4  Al2(SO4)3 + 6 H2O Chem121–SU12PracticeforExam2
Question 16: Show the nuclear equation for the alpha decay of Kr‐76. →
Question 17: A. You have 1000 parent nuclei, which decay to daughter nuclei. If you wait until the half‐life, how many parent nuclei do you have? How many daughter nuclei do you have? 500 parent 500 daughter B. You wait 6 half‐lives. How many parent nuclei and daughter nuclei do you have? 1000 parent 0 daugther 500 parent 250 parent 1 half‐life 500 daughter 2nd half‐life 750 daughter 3rd half‐life 62 parents Start 4th half‐life 930 daughter 5th half‐life 31 parents 961 daughter 6th half‐life 15 parent 977 daughter 125 parent 875 daughter