LUOA chemistry semester exam review 2023 with complete solution

LUOA chemistry semester exam review 2023 with complete solution How many molecules are in 3.9 moles of water? 2.3 x 10^24 molecules of water How many moles are in 3.75 x 10^24 molecules of CO2? 6.23 moles How many moles are in 1.16 x 10^25 atoms of H2CO3? 19.3 moles of H2CO3 The molar mass of Cu(OH)2 is _________ grams per mole. (Hint: Answers might vary slightly, but should still fall within an acceptable range for the correct answer) 97.55 How many moles are in 132.3 grams of carbon dioxide? (Hint: Answers might vary slightly, but should still fall within an acceptable range for the correct answer) 3.007 moles How many grams are in 3.396 moles of Al2S3? (Hint: Answers might vary slightly, but should still fall within an acceptable range for the correct answer) 509.9 grams Calculate the mass of carbon in 250 g C2H6 199.72 grams Calculate the mass of hydrogen in 250 g C2H6 50.28 grams Calculate the mass of hydrogen in 250 g of C2H3O2 12.83 grams Methyl acetate has a chemical composition of 48.64% carbon, 8.16% hydrogen, and 43.20 % oxygen. What is the empirical formula? C3H6O2 A(n) __________formula is one that shows the lowest whole number ratio of the elements in a compound empirical If the empirical formula of a compound is C2OH4 and has a molar mass of 88 g/mol, what is its molecular formula? C4O2H8 Write the formula for copper (II) sulfate hexahydrate. CuSO4 ∙ 6H2O N2+ 3H2-- 2NH3 How many moles of ammonia are produced when 5 moles of hydrogen reacts with excess nitrogen? 3.3 mol N2+ 3H2-- 2NH3 In a certain reaction, 5.0 moles of hydrogen is reacted with excess nitrogen. To determine how many moles of ammonia (NH3) are produced based on the 5 mols of hydrogen, what conversion factor(s) should be used? (choose all that apply) (2 mol NH3)/(3 mol H2) (3 mol H2)/(2 mol NH3) 2NO(g) + O2 (g) -- 2NO2 How many grams of NO are required to react fully with 5.00 mol of O2? 300 g 2 NO(g) + O2 (g) -- 2 NO2 (g) What mass of NO2 is produced by the reaction of 2.40 mol NO with excess oxygen? 110.4 g 4 Fe(s) + 3O2(g) -- 2Fe2O3(g) In a certain reaction, 27.3 g of iron is reacted with 45.8 g of Oxygen. What is the limiting reactant? Fe 4 Fe(s) + 3O2(g) --2Fe2O3(g) In a certain reaction, 27.3 g of iron is reacted with 45.8 g of Oxygen. How many grams of the excess reactant remain after the reaction is complete 33.9 g What pieces of information do we need in order to calculate percent yield? the maximum amount possible of product and the amount experimentally recovered What factors can contribute to a percent yield that is less than 100%? -unwanted side reaction -incomplete reaction -spills during the experiment Select the best description of the path of gas particles in a given sample of gas? straight path which changes upon collisions with other particles Pressure is: force/area ___ kPa = 14.7 psi 101.3 kPa Identify the correct ranking of intermolecular bonds or forces in order from strongest to weakest is: hydrogen bond, dipole-dipole force, dispersion force In water molecules, the oxygen atoms have a slightly _____ charge, while the hydrogen atoms has a slightly _____ charge. negative; positive The O-H covalent bond in a water molecule is described as _____. very polar Dipole-dipole forces are _________? Intermolecular force between polar molecules Which is not true of most solids? They move randomly to fill their container. Which type of crystal is made of atoms that are all covalently bonded to their nearest neighbors? network solid Crystals can be classified into how many different crystal systems (or shapes)? seven In which type of crystal solid are the particles at the lattice points held together by dispersion forces or hydrogen bonds? molecular Which statement accurately describes the rate of evaporation and the rate of condensation in a sealed container The rates are equal and the water level remains the same. Which of the following phase changes does NOT require energy condensation A puddle of liquid is evaporating. What happens to the temperature of the water in the puddle? decreases What are two ways that a liquid can be turned into a gas? Increase the temperature or decrease the pressure. Select the best explanation for what keeps a balloon inflated? gas particles colliding with the inside of the balloon The following gases are at STP. Which one will diffuse the fastest? F2, CO2, He, SO2, NO, NH3 He _______torr = One atm 760 torr 1.38 atm = ______ mm Hg. 1050 mm Hg When gas escapes through a small hole in its container is called _____. effusion Oxygen gas is 21 % of Earth's atmosphere. If the atmospheric pressure is 457mmHg, what is the partial pressure of oxygen at that location? 96 mmHg Which of the following is not an intermolecular force? covalent bonding The halogen with the highest boiling point is _____ due to its _____. iodine; strong dispersion forces Identify the compound has the lowest boiling point? NH3 HCl CH4 CH4 How many hydrogen atoms are present in 0.46 moles of NH3? 8.3 x 10^23 Hydrogen atoms How many molecules are in 1.95 moles of H2O? 1.17 x 10^24 molecules How many molecules are in 11.5 mol of H2O? 6.92 x 10^24 How many atoms of Hydrogen atoms are found in 3.94 mol of NH5? 1.19 x 10^25 Hydrogen Atoms How many moles are in 20.50 grams of NH3? 1.204 moles What is the percent composition of sulfur in N2S2? 69.6% What is the empirical formula for C3H6O9? CH2O3 Vinegar, which has many applications, has the following percent composition: 39.9% carbon, 6.7% hydrogen and 53.4% Oxygen. What is the empirical formula? CH2O A compound has a chemical composition of 97.6 g carbon, 4.9 g hydrogen, 52 g oxygen, 45.5 g nitrogen. What is the empirical formula? C5H3O2N2 What type of compound can have both an empirical formula and molecular formula? covalent 26 g of zinc combines with 12.8 g of sulfur. What is the empirical formula of zinc sulfide? ZnS What is the name of the procedure which determines the composition of the elements in a compound? elemental analysis Find the percent composition of water in barium chloride dihydrate. Round answer to the nearest whole number. 17% If the empirical formula of a compound is CH2 and the molar mass is 70.0 g/mol, what is the molecular formula? C5H10 Name the following hydrate CuSO4 · 5 H2O. copper (II) sulfate pentahydrate Fluorine gas reacts with a solution of sodium bromide in a single-replacement producing aqueous sodium fluoride and bromine gas. Which of the following is the correct balanced equation for this reaction? F2(g) + 2 NaBr (aq) --2NaF (aq) + Br2(l) The coefficient of a particular substance in a balanced equation represents moles, molecules and formula units