CHEMISTRY 1180 Practice Exam 4 Ebbing and Gammon PLEASE NOTE THIS IS A PRACTICE EXAM AND NOT A STUDY GUIDE Use the objective lists for chapters 3 and 4 as your study guide You must show all work to receive credit for a calculation 1 An element was found to consist of only two isotopes The first isotope has a mass of 11 213 amu and was 75 4 abundant The other isotope had a mass of 13 347 amu Calculate the weighed atomic mass of this element Answer 11 7 amu 2 Give the empirical formula for each of the following compounds a C6 H8 O4 b K2 C4 H4 O6 c Al2 C2 O4 3 d C3 H8 N2 O4 P empirical formula of c is AlC3O6 3 Vitamin C has an empirical formula of C3 H4 O3 and a formula mass of about 180 amu What is the true or molecular formula of Vitamin C answer C6H8O6 4 Calculate the molar mass of Ca3 PO4 2 5 Calculate the number of formula units of Ca3 PO4 2 in 16 35 g of Ca3 PO4 2 Answer 3 174 x 1022 F U 6 Calculate the number of oxygen atoms in 16 35 g of Ca3 PO4 2 Answer 2 539 x 1023 atoms oxygen 7 Calculate the weight percent of phosphorus in Ca3 PO4 2 8 Balance the following reactions Answer 310 18 g Answer 19 97 phosphorus a H2 SnCl6 H2 S SnS2 HCl b C6 H5 COOH O2 9 Consider the reaction Fe2 O3 CO2 CO H2 O Fe CO2 a Calculate the stoichiometric amount of carbon monoxide needed to react with 75 0 g of Fe2 O3 Answer 39 46 g carbon monoxide b When 75 0 g of Fe2 O3 reacted 49 38 g of iron metal were recovered Calculate the percent yield for this reaction Answer 94 1 yield of Iron 10 Consider the reaction Li F2 LiF When 15 0 g of Li and 25 0 g of F2 are placed in a reaction flask and allowed to react Answer the following questions a What is the limiting reagent b What is the theoretical yield of LiF Answer 34 1g c How many grams of excess reagent will remain once the reaction has stopped Answer 5 87 g d Which statement best describes the contents of the reaction flask once the reaction has gone to completion a The flask contains only LiF b The flask contains both LiF and Li c The flask contains both LiF and F2 d The flask contains Li F2 and LiF e None of the above choices 11 Complete the following sentences mixture a A solution is a b Aqueous solutions are formed when water is the c The concentration of a solution is always expressed in terms of the 12 Calculate the mass of potassium sulfate FM 174 27 needed to make 165 mL of 125 M potassium sulfate solution answer 3 59g 13 What volume of 346M KOH must be used to make 150 mL of 100 M KOH solution answer 156 mL 14 Consider the reaction 2CuSO4 aq 4HI aq 2CuI aq 2H2 SO4 aq I2 aq What is the molarity of the hydroiodic acid if 17 85 mL of HI solution reacts exactly with answer 5991M HI 11 72 mL of 4562 M CuSO4 solution 15 Complete the following sentences a Any substance whose aqueous solution contains ions is called a n b Any substance forming an aqueous solution containing no ions is called a n c Those substances that are present in solution entirely as ions are called whereas substances that are present partly as ions and partly as molecules are called 16 Calculate the concentration of permanganate ions in 015 M iron III permanganate concentration What property of soluble salts like iron III permanganate allow ion concentrations to be easily calculated 17 18 a Complete and balance the following double displacement reactions b Give the ionic and net ionic reactions for each If no reaction occurs write N R in place of the net ionic reaction a Fe OH 3 s HNO3 aq b HClO aq c K3PO4 aq d When aqueous solutions of copper II bromide and sodium hydroxide react in a double displacement reaction a bluish gel like precipitate is formed e The double displacement reaction between hydrosulfuric acid and lead II acetate produces a yellow solid NH4OH aq NaCl aq Consider the following reaction K2Cr2O7 HCl KCl CrCl3 H2O Cl2 a determine the oxidation state of all elements in this reaction b Which element is oxidized c Which element is reduced d Which compound is the oxidizing agent e Which compound is the reducing agent f Balance the reaction when balanced the coefficient of Cl2 will be 3 19 Using the activity series provided in the lecture notes complete and balance the following reactions Write N R after the arrow if no reaction occurs Mg Cr3 Zn H H2 Au3 Hg Fe2 20 is a dissolved non electrolyte is a soluble salt Draw molecular level representations of these substances in the water filled containers provided weak electrolyte 21 rSs MSM is a weak electrolyte FSF non electrolyte soluble salt Consider the following reactions a NaCl aq b 2 CH3OH l AgNO3 aq AgCl s 3 O2 g 2 CO2 g c CuO s Cu s d S s e Mg s 2 O2 g NaNO3 aq 4 H2O l O2 g Ca s CaSO4 s FePO4 s Mg3 PO4 2 s Fe s Match each reaction with its correct description a formation reaction b metathesis reaction d combustion reaction e decomposition reaction c single displacement reaction