Pre Exam 3 Homework with Answers(2) (1).docx - Pre Exam 3 Homework with Answers 1 In this reaction what is the coefficient for calcium oxide CaO(s CO2(g

# Pre Exam 3 Homework with Answers(2) (1).docx - Pre Exam 3...

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Pre Exam 3 Homework with Answers1) In this reaction, what is the coefficient for calcium oxide?CaO(s) + CO2(g) CaCO3(s)A) 1B) 2C) 3D) 4E) 5Answer: A2) In the following reaction, when the equation is correctly balanced, what is the correct coefficient for H2?Fe(s) + HCl(aq) FeCl3(aq) + H2(g)3) What is the classification for this reaction?SO3 (g) + H2O (l) H2SO4 (l)A) decompositionB) combinationC) replacementD) double replacementE) oxidation reduction
Answer: B4) How many molecules of water, H2O, are present in 75.0 g of H2O?75.0 g of H2O X 1 mole H2O X 6.02 X 1023 molecules = 2.51 × 1024molecules 18.0 g of H2O 1 mole Note: 2.51 × 1024molecules (scientific notation) = 25.1 × 1023molecules 5) One mole of particles of any substance contains how many particles?6) How many moles of water, H2O, are present in 75.0 g of H2O?A) 4.41 moles
B) 4.17 molesC) 75.0 molesD) 7.50 molesE) 1.35 × 103 moles Answer: B75.0 g of H2O X 1 mole H2O = 4.17 moles 18.0 g of H2O 7) Calculate the molar mass of magnesium chloride, MgCl2.Obtain atomic mass from Periodic table for Mg (24.3) and 2X Cl (2 X 35.5) and add24.3 + 71.0 = 95.3 8) What is the molar mass of Mg3(PO4)2, a substance formerly used in medicine as an antacid?Obtain atomic mass from Periodic table for 3 X Mg (3X24.3) , 2 X P (2 X 31.0) and 8 X O (8X16.0)) and then add
(3X24.3) = 72.92 X 31.0 = 62.08X16.0 = 128.0262.92Mg + O22MgO9) The number of moles of oxygen gas needed to react with 4.0 moles of Mg is4.0 moles of Mg X 1 mole of O2= 2 mole of O22.0 moles of Mg 10) In an endothermic reaction,A) heat flows out of the system.B) energy is absorbed by the system.C) the temperature of the system increases.D) the products have less energy that the reactants.E) the products have the same energy that the reactantsAnswer: B
In an endothermic reaction, heat flows into the system with the result that energy is absorbed by the system and the products have higher energy than the reactants

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