SCIN131-Introduction to Chemistry-APUS-Lesson 3 Assignment

Part 1 of 4 - 8.0/ 8.0 Points Question 1 of 12 4.0/ 4.0 Points What is the molar mass of aluminum sulfate?  A.315.2 g/mol  B.342.2 g/mol  C.278.0 g/mol  D.306.2 g/mol  E.123.0 g/mol Answer Key: B Question 2 of 12 4.0/ 4.0 Points Which of the following compounds has the highest mass percent of "O"?  A.Mn3O2  B.MnO  C.Mn2O3  D.MnO2  E.none of the above Answer Key: D

Part 2 of 4 - 16.0/ 16.0 Points Question 3 of 12 4.0/ 4.0 Points When solid NaCl is stirred into water, which of the following is NOT true?  A.The NaCl will fail to dissociate.  B.The solution will taste salty.  C.The solution will conduct electricity.  D.Individual sodium and chloride ions are present.  E.none of the above Answer Key: A Question 4 of 12 4.0/ 4.0 Points Which of the following everyday substances does NOT typically contain an acid?  A.lemons  B.vinegar  C.limes  D.soap  E.all of the above Answer Key: D Question 5 of 12 4.0/ 4.0 Points An aqueous solution is:  A.water with another compound dissolved in it.  B.any liquid with another compound dissolved in it.  C.an ionic compound with water dissolved in it.  D.water with a molecular compound dissolved in it.  E.none of the above Answer Key: A Question 6 of 12 4.0/ 4.0 Points What are the coefficients for the following reaction when it is properly balanced?___O2 + ___CH4 → ___CO2 + ___H2O  A.2, 1, 1, 2  B.2, 3, 2, 2  C.2, 1, 3, 1  D.1, 3, 2, 1  E.none of the above Answer Key: A

Part 3 of 4 - 16.0/ 16.0 Points Question 7 of 12 4.0/ 4.0 Points How many grams of water are made from the reaction of 4.0 grams of hydrogen gas? Given the reaction: 2H2 + O2 → 2H2O  A.72  B.36  C.18  D.4.5  E.not enough information Answer Key: B Question 8 of 12 4.0/ 4.0 Points Consider the following generic chemical equation: 2W + 3X → 3Y + Z When 5 units of W and 6 units of X are allowed to react, the limiting reactant would be:  A.Y  B.X  C.W  D.Z  E.There is no limiting reactant in this situation. Answer Key: B Question 9 of 12 4.0/ 4.0 Points How many moles of sodium metal are needed to make 3.6 moles of sodium chloride? Given the reaction: 2Na + Cl2 → 2NaCl  A.3.6  B.7.2  C.1.8  D.0.9  E.not enough information Answer Key: A Question 10 of 12 4.0/ 4.0 Points Given that 4 NH3 + 5 O2 → 4 NO + 6 H2O, when 4.50 mol of H2O are formed, the amount of NO formed is  A.3.00 mol.  B.1.50 mol.  C.4.50 mol.  D.6.75 mol.  E.none of the above Answer Key: A

Part 4 of 4 - 10.0/ 10.0 Points Question 11 of 12 5.0/ 5.0 Points Vitamin C is known chemically by the name ascorbic acid. Determine the empirical formula of ascorbic acid if it is composed of 40.92% carbon, 4.58% hydrogen, and 54.50% oxygen. H = 1 g/mol C = 12 g/mol O = 16 g/mol Then we divide A.M. / % For the carbon: 40.92 / 12 ~ 3.4 For the hydrogen: 4.58 / 1 = 4.58 For the oxygen: 54.5 / 16 ~ 3.4 Then we divide the smallest result to each element: C = 3.4 / 3.4 = 1 H = 4.6 / 3.4 = 1.35 O = 3.4 / 3.4 = 1 by multiplying by another number that will turn it into a complete number: C = 1 x 3 = 3 H = 1.35 x 3 = 4,05 ~ 4 O = 1 x 3 = 3 The empirical formula for the ascorbic acid is: C3H4O3 Question 12 of 12 5.0/ 5.0 Points Determine the empirical formula of a compound containing 60.3% magnesium and 39.7% oxygen. Mg = 24.3 g/mol O = 16 g/mol By dividing given percentage with respective molar mass 60.3/24.3 = 2.48 Mg 39.7/16.0 = 2.48 O The relative numbers of atoms are in a 1:1 ratio, so the emperical formula is MgO  Feedback: Please see Chapter 6 for a problem like this.

Question 1 of 12 4.0/ 4.0 Points How many moles of fluorine are in 3.2 moles of xenon hexafluoride?  A.19.2  B.12.8  C.22.4  D.16  E.none of the above Answer Key: A Question 2 of 12 4.0/ 4.0 Points What is the mass percent of chlorine in hydrochloric acid?  A.2.8  B.70.1  C.97.2  D.35.5  E.none of the above Answer Key: C

Part 2 of 4 - 16.0/ 16.0 Points Question 3 of 12 4.0/ 4.0 Points Which of the following equations is NOT balanced properly?  A.4NH3 + 14O2 → 4NO2 + 6H2O  B.2NaHCO3 → Na2CO3 + CO2 + H2O  C.2Cr + 6HCl → 2CrCl3 + 3H2  D.Cr2(SO4)3 + 6KOH → 2Cr(OH)3 + 3 K2SO4  E.none of the above Answer Key: A Question 4 of 12 4.0/ 4.0 Points Before a chemical equation can be written, one must know  A.the molar mass of all the compounds.  B.the number of moles of all reactants and products.  C.the atomic mass of all the elements involved.  D.the symbols and formulas of all reactants and products.  E.none of the above. Answer Key: D Question 5 of 12 4.0/ 4.0 Points What are the coefficients for the following reaction when it is properly balanced?___HCl + ___Mg → ___MgCl2 + ___ H2  A.2, 1, 2, 2  B.2, 1, 1, 1  C.1, 2, 1/2, 1  D.1, 1, 1, 2  E.none of the above Answer Key: B Question 6 of 12 4.0/ 4.0 Points When the equation, ___N2 + ___H2 → ___NH3 is balanced, the coefficient of hydrogen is:  A.1  B.2  C.4  D.3  E.none of the above Answer Key: D

Part 3 of 4 - 12.0/ 16.0 Points Question 7 of 12 4.0/ 4.0 Points The theoretical yield of a reaction is 75.0 grams of product and the actual yield is 42.0g. What is the percent yield?  A.75.0  B.178  C.56.0  D.31.5  E.none of the above Answer Key: C Question 8 of 12 4.0/ 4.0 Points If the theoretical yield of a reaction is 42.0 grams of product and the percent yield is 75%. How many grams were actually produced?  A.32  B.5400  C.56  D.1.8  E.none of the above Answer Key: A Question 9 of 12 4.0/ 4.0 Points Consider the following generic chemical equation: 2A + 5B → C + 3D If you react 4 units of A with 10 units of B, which statement is TRUE?  A.Substance B will be the limiting reactant.  B.Substance C cannot be formed from this reaction.  C.There is just enough of A and B so that everything reacts completely.  D.Substance A will be the limiting reactant.  E.none of the above Answer Key: C Question 10 of 12 0.0/ 4.0 Points How many grams of water are made from the reaction of 16.0 grams of oxygen gas?Given the reaction: 2H2 + O2 → 2H2O  A.16  B.18  C.9  D.36  E.not enough information Answer Key: B

Part 4 of 4 - 5.0/ 10.0 Points Question 11 of 12 0.0/ 5.0 Points What is the theoretical yield in grams of CuS for the following reaction given that you start with 15.5 g of Na2S and 12.1 gCuSO4? Reaction: Na2S + CuSO4 → Na2SO4 + CuS Molar Mass of ( Na2S ) = 78.06 g/mol Given 15.5 g counts to 15.5 g / 78.06 = 0.198 moles of Na2S Molar Mass of ( CuSO4) = 159.64 g / mol  12.1 g / 159.64 = 0.0758 moles CuSO4 the reaction is Na2S + CuSO4 ------> Na2SO4 + CuS the ratio between Na2S and CuSO4 is 1 : 1 so CuSO4 is the limiting reactant. We would get 0.0758 mole CuS Molar Mass of CuS = 95.54 g/mol) 0.0758 mole x 95.54 g/mol = 7.24 g of CuS Question 12 of 12 5.0/ 5.0 Points What is the limiting reactant for the reaction below given that you start with 10.0 grams of Al and 19.0 grams of O2? Reaction: 4Al + 3O2 → 2Al2O3 Molar mass of Al = 27g/mol  Molar mass of O2 = 32g/mol  number of moles of Al = 10g / 27g/mol = 0.37 mol Al  number of moles of O2 = 19g / 32 g/mol = 0.59 mol O2  Taking the moles of each substance and dividing it by the coefficient of the balanced equation:  4Al + 3O2 → 2Al2O3 For Al: 0.37 / 4 = 0.09  For O2: 0.59 / 3 = 0.197  The lowest number indicates the limiting reagent. Hence Aluminum is limiting reagent.

Part 1 of 4 - 8.0/ 8.0 Points Question 1 of 12 4.0/ 4.0 Points One mole of ammonium nitrate contains:  A.2 moles of nitrogen.  B.1 mole of nitrogen.  C.2 moles of oxygen.  D.3 moles of hydrogen.  E.none of the above Answer Key: A Question 2 of 12 4.0/ 4.0 Points The empirical formula of a compound:  A.is the same as the molecular formula.  B.indicates the simplest ratio of atoms in the compound.  C.describes the mass relationships in a molecule.  D.indicates the structure of the molecule.  E.none of the above Answer Key: B

Part 2 of 4 - 16.0/ 16.0 Points Question 3 of 12 4.0/ 4.0 Points All of the following compounds are soluble in water EXCEPT  A.PbCl2.  B.NH4Cl.  C.CaCl2.  D.FeCl3.  E.NaCl. Answer Key: A Question 4 of 12 4.0/ 4.0 Points When the equation __Ca3N2 + __H2O → __Ca(OH)2 + __NH3 is balanced, the coefficient of H2O is:  A.3  B.2  C.6  D.12  E.none of the above Answer Key: C Question 5 of 12 4.0/ 4.0 Points What are the coefficients for the following reaction when it is properly balanced?___O2 + ___CH4 → ___CO2 + ___H2O  A.2, 1, 1, 2  B.2, 3, 2, 2  C.2, 1, 3, 1  D.1, 3, 2, 1  E.none of the above Answer Key: A Question 6 of 12 4.0/ 4.0 Points Which of the following would NOT be a product from mixing hydrochloric acid with a solution of sodium sulfite?  A.NaCl (aq)  B.H2O (l)  C.SO2 (g)  D.H2 (g)  E.none of the above Answer Key: D

Part 3 of 4 - 16.0/ 16.0 Points Question 7 of 12 4.0/ 4.0 Points Many metals react with halogens to give metal halides. For example, 2 Al (s) + 3 Cl2(g) → 2 AlCl3 (s) If you begin with 13.5 g of aluminum,  A.you will need 23.6 g Cl2 for complete reaction and will produce 66.7 g of AlCl3.  B.you will need 53.2 g Cl2 for complete reaction and will produce 66.7 g of AlCl3.  C.you will need 11.8 g Cl2 for complete reaction and will produce 49.0 g of AlCl3.  D.you will need 26.6 g Cl2 for complete reaction and will produce 49.0 g of AlCl3.  E.none of the above Answer Key: B Question 8 of 12 4.0/ 4.0 Points Consider the following generic chemical equation: 2A + 5B → C + 3D If you react 4 units of A with 10 units of B, which statement is TRUE?  A.Substance B will be the limiting reactant.  B.Substance C cannot be formed from this reaction.  C.There is just enough of A and B so that everything reacts completely.  D.Substance A will be the limiting reactant.  E.none of the above Answer Key: C Question 9 of 12 4.0/ 4.0 Points A chemist wishes to perform the following reaction: N2 + 3 H2 → 2 NH3 If only 14.0 g of N2 is available, what is the minimum amount, in grams, of H2 needed to completely react with this quantity of N2?  A.3.03 g  B.1.01 g  C.1.51 g  D.6.06 g  E.none of the above Answer Key: A Question 10 of 12 4.0/ 4.0 Points How many grams of sodium metal are needed to make 29.3 grams of sodium chloride? Given the reaction: 2Na + Cl2 → 2NaCl  A.5.75  B.11.5  C.46.0  D.23.0  E.not enough information Answer Key: B

Part 4 of 4 - 9.0/ 10.0 Points Question 11 of 12 4.0/ 5.0 Points Sodium peroxide (Na2O2) reacts with water to form sodium hydroxide and oxygen gas. Write a balanced equation for the reaction and determine how much oxygen in grams is formed by the complete reaction of 35.23 g Na2O2. 2Na2O2(s)+2H2O(l)----------->4NaOH(aq)+O2(g)  First converting grams of sodium peroxide to moles of sodium peroxide using the molar mass:  33.57g Na2O2 x (1mole Na2O2 / 77.98g Na2O2)= 0.4305moles Na2O2 By Equation for every 2 moles of Na2O2 in the reaction, there is one mole of O2. 0.4305 moles Na2O2 x (1 mole O2 / 2 moles Na2O2) = 0.2152 moles O2 Converting to grams using molar mass: 0.2152 moles O2 x (32g O2 / 1 mole O2) = 6.888g O2 Comment: 7.23 g O2 Question 12 of 12 5.0/ 5.0 Points A 9.56-g sample of aluminum completely reacts with oxygen to form 13.34 g of aluminum oxide. Use this data to calculate the mass percent composition of aluminum in aluminum oxide. Completely reacts means that all of the Al is in aluminum oxide. So mass percent of aluminum in aluminum oxide is 9.56/13.34 * 100% = 71.66% Feedback: Please see Chapter 6 for help with calculating mass percents of compounds.

Part 1 of 4 - 8.0/ 8.0 Points Question 1 of 12 4.0/ 4.0 Points `Let's be honest, caffeine (C8H10N4O2) makes the world go 'round. What is the mass in grams of 2.00 moles of this wonderdrug?  A.194  B.97  C.388  D.24  E.48 Answer Key: C Question 2 of 12 4.0/ 4.0 Points `Your physician has told you to increase your potassium intake by eating more bananas. The problem is, he wrote this down in terms of moles and not bananas. He said to eat at least 0.0216 moles of potassium per day. An average banana contains about 422 mg of potassium. How many bananas do you need to eat each day?  A.1  B.2  C.3  D.4  E.5 Answer Key: B Feedback: Good. See section 6.3

Part 2 of 4 - 16.0/ 16.0 Points Question 3 of 12 4.0/ 4.0 Points `Suppose you pour a beaker of ammonium nitrate solution into a beaker containing a solution of sodium chloride. What type of reaction would you expect to occur?  A.oxidation-reduction  B.gas evolution  C.precipitation  D.acid-base neutralization  E.no reaction Answer Key: E Feedback: Good. See sections 7.5-7.6 Question 4 of 12 4.0/ 4.0 Points How is the best way to describe an aqueous solution?  A.water that contains a dissolved compound  B.any liquid that contains a dissolved compound  C.an ionic compound containing water dissolved in it.  D.all of these are accurate Answer Key: A Feedback: Good. see section 7.5 Question 5 of 12 4.0/ 4.0 Points Which of the following compounds is soluble?  A.copper carbonate  B.strontium carbonate  C.sodium carbonate  D.calcium carbonate Answer Key: C Feedback: Good. See the solubility table Question 6 of 12 4.0/ 4.0 Points When the reaction below is balanced, what number belongs in front of KOH?       ___ H3PO4   +  ___  KOH -->  _____ K3PO4   +   ____ H2O  A.6  B.1  C.2  D.3 Answer Key: D Feedback: Good. See section 7.4

Part 3 of 4 - 16.0/ 16.0 Points Question 7 of 12 4.0/ 4.0 Points My grandmother left me some silver years ago.  I opened the box containing the silver and it had tarnished.  Using the equation below, if I had 300 g of silver that had tarnished and 175g H2S, which would be the limiting reactant? 2 Ag(s) + H2S(g) → Ag2S(s) + H2(g)  A.silver  B.silver sulfide  C.hydrogen  D.hydrogen sulfide  E.There is no limiting reactant in this case Answer Key: A Feedback: Good. see section 8.6 Question 8 of 12 4.0/ 4.0 Points Solid Iron (III) reacts with oxygen gas to form iron (III) oxide, which is the compound we see when rust is present.  Based on this information, which of the following is true? 4Fe + 3O2 ---> 2Fe2O3  A.4 moles of iron will need 2 moles of oxygen gas to fully react  B.12 moles of iron, if reacted completely, can produce 8 moles of iron (III) oxide.  C.9 moles of oxygen can produce 9 moles of Iron (III) oxide  D.6 moles of oxygen can react completely to produce 6 moles of iron (III) oxide.  E.none of the above Answer Key: E Feedback: Good. See section 8.6 Question 9 of 12 4.0/ 4.0 Points Percent yield is very important in terms of money. The higher the percent yield, the more of a product you can make. If you are working for a drug company and your theoretical yield is 120 kg, but you actually made 105 kg, what is your percent yield?  A.15.0%  B.114%  C.87.5%  D.8.75% Answer Key: C Feedback: Good. See section 8.6 Question 10 of 12 4.0/ 4.0 Points If I need 2 slices of bread, 3 slices of ham, and 1 slice of cheese to make 1 sandwich, how many slices of bread are needed to make 5 sandwiches?  A.12  B.2  C.5  D.10  E.6 Answer Key: D Feedback: Good. See section 8.7

Part 4 of 4 - 0.0/ 10.0 Points Question 11 of 12 0.0/ 5.0 Points Determine the empirical formula for a compound if it is composed of 63.56% carbon, 6.00% hydrogen, 9.27% nitrogen, and 21.17% oxygen.   Molar masses of Carbon : 12.011 g/mol Hydrogen: 1.008 g/mol Nitrogen: 14.007 g/mol Oxygen : 15.999 g/mol When we divide the given percentages by respective molar masses we get, Carbon: 63.56/12.011 =  5.2918 mol Hydrogen: 6.00/1.008 = 5.9523 mol Nitrogen: 9.27/14.007 = 0.6618 mol Oxygen: 21.17/15.999 = 1.3232 mol Now dividing each of these moles with the least one we get, Carbon: 5.2918/0.6618 = 8 Hydrogen : 5.9523/0.6618 = 9 Nitrogen: 0.6618/0.6618 = 1 Oxygen: 1.3232/0.6618 = 2So the Empirical formula would be : C8H9NO2 Feedback: This deals with writing chemical equations using chemical formulas and using the law of conservation to balance it. Question 12 of 12 0.0/ 5.0 Points Assume you take 45.5g of sodium phosphate and react it with excess hydrochloric acid to produce 35.5 g sodium chloride and excess water.  Write the balanced equation and determine your percent yield.  You must show all work to receive credit. Sodium phosphate, Na3PO4, reacts with HCl to form H3PO4 and NaCl. (How is water formed here ???) Na3PO4+3HCl ----> H3PO4+3NaCl---> Balanced Equatio 1 mole of Na3PO4 (163.94 g/mol) is required to form 3 moles of NaCl (58.44 g/mol) Percent yield = Actual yield divided by theoritical yield so 45.5 g of Na3PO4 must produce : 3(58.44/163.94)*45.5 = 48.65 g but actually we can see that only 35. Feedback: Please see Chapter 8 for help with percent yields.

Part 1 of 4 - 8.0/ 8.0 Points Question 1 of 12 4.0/ 4.0 Points What is the mass of 1.56 × 1021 atoms of magnesium in grams?  A.4.72 × 10-5  B.0.0630  C.1.07 × 10-4  D.0.142  E.none of the above Answer Key: B Question 2 of 12 4.0/ 4.0 Points The empirical formula of a compound:  A.is the same as the molecular formula.  B.indicates the simplest ratio of atoms in the compound.  C.describes the mass relationships in a molecule.  D.indicates the structure of the molecule.  E.none of the above Answer Key: B

Part 2 of 4 - 16.0/ 16.0 Points Question 3 of 12 4.0/ 4.0 Points What type of a reaction occurs when a hydrochloric acid solution is mixed with a sodium bicarbonate solution?  A.acid-base neutralization  B.precipitation  C.oxidation-reduction  D.gas evolution  E.no reaction Answer Key: D Question 4 of 12 4.0/ 4.0 Points Which of the following statements about balancing reactions is FALSE?  A.Subscripts are multiplied by the coefficients to determine the number of atoms in a compound.  B.When coefficients are added the type of compounds is changed in the chemical reaction.  C.If there is no coefficient or subscript, a one is implied.  D.Coefficients are added to compounds to ensure both sides of the reaction have equal numbers of each atom.  E.All of the above statements are true. Answer Key: B Question 5 of 12 4.0/ 4.0 Points Which of the following is NOT evidence that a chemical reaction has occurred?  A.gas formation when chemicals are contacted with each other  B.color change when chemicals are contacted with each other  C.solid formation when chemicals are contacted with each other  D.emission of light when chemicals are contact with each other  E.All of the above are evidence of a chemical reaction. Answer Key: E Question 6 of 12 4.0/ 4.0 Points A reaction which forms a solid product is an example of a(n)________.  A.combustion reaction  B.gas evolution reaction  C.oxidation-reduction reaction  D.precipitation reaction  E.none of the above Answer Key: D

Part 3 of 4 - 16.0/ 16.0 Points Question 7 of 12 4.0/ 4.0 Points Consider the following reaction: 2 Mg + O2 → 2 MgO △H rxn = -1203 kJ Calculate the amount of heat (in kJ) associated with complete reaction of 4 moles of Mg.  A.-601.5 kJ  B.-4812 kJ  C.-1203 kJ  D.-2406 kJ  E.none of the above Answer Key: D Question 8 of 12 4.0/ 4.0 Points A chemist wishes to perform the following reaction: N2 + 3 H2 → 2 NH3 If only 14.0 g of N2 is available, what is the minimum amount, in grams, of H2 needed to completely react with this quantity of N2?  A.3.03 g  B.1.01 g  C.1.51 g  D.6.06 g  E.none of the above Answer Key: A Question 9 of 12 4.0/ 4.0 Points How many grams of water are made from the reaction of 4.0 grams of hydrogen gas? Given the reaction: 2H2 + O2 → 2H2O  A.72  B.36  C.18  D.4.5  E.not enough information Answer Key: B Question 10 of 12 4.0/ 4.0 Points Given that 4 NH3 + 5 O2 → 4 NO + 6 H2O, if 3.00 mol NH3 were made to react with excess of oxygen gas, the amount of H2O formed would be  A.6.00 mol.  B.3.00 mol.  C.2.00 mol.  D.4.50 mol.  E.none of the above Answer Key: D

Part 4 of 4 - 0.0/ 10.0 Points Question 11 of 12 0.0/ 5.0 Points An unknown acid has a molar mass of 60.05 g/mol. Given the following percent composition, what is the molecular formula? 40%C, 6.7% H, 53.3% O H = 1 g/mol C = 12 g/mol O = 16 g/mol Then we divide A.M. / % For the carbon: 40 / 12 ~ 3.33 For the hydrogen: 6.7 / 1 = 6.7 For the oxygen: 53.3 / 16 ~ 3.33 Then we divide the smallest result to each element: C = 3.33 / 3.33 = 1 H = 6.7 / 3.33 = 2 O = 3.33 / 3.33 = 1 The empirical formula is: CH2O Empirical Weight = 12.011+2(1.008)+15.999= 30.026 Molar Weight = 60.05 So, its almost 2 times, which makes the Molecular formula as C2H4O2 (Molar mass = 60.052) Question 12 of 12 0.0/ 5.0 Points Sodium peroxide (Na2O2) reacts with water to form sodium hydroxide and oxygen gas. Write a balanced equation for the reaction and determine how much oxygen in grams is formed by the complete reaction of 35.23 g Na2O2. When Sodium Peroxide reacts with water to form sodium hydroxide and oxygen gas, the balanced equation is given as follows. 2Na2O2 + 2 H2O ---> 4 NaOH +  O2  We need to first convert grams of sodium peroxide to moles of sodium peroxide using the molar mass:  35.23g Na2O2 x (1mole Na2O2 / 77.98g Na2O2)= 0.4518 moles Na2O2  We know that for every 2 moles of Na2O2 in the reaction, there is one mole of O2.  0.4518 moles Na2O2 x (1 mole O2 / 2 moles Na2O2) = 0.2259 moles O2  Convert to grams using molar mass:  0.2152 moles O2 x (32g O2 / 1 mole O2) = 7.2288 g O2