SCI 131 WEEK QUIZ QUESTIONS AND ANSWERS

Tests & Quizzes SCI 131 WEEK QUIZ QUESTIONS AND ANSWERS Lesson 05 - Week 05 Quiz Return to Assessment List Part 1 of 1 - 100.0 Points Question 1 of 25 `Sodium and chlorine are very dangerous by themselves. However, when we combine them together in a chemical 4.0 Points reaction, we eat it--it's table salt: 2Na + Cl2 → 2NaCl. If I want to make 50.0 g of my own salt (because I can and that's how I roll), how much elemental sodium would I need? NOTE: All numbers located immediately after elemental symbols should be considered subscripts. A. 50.0 g B. 100.0 g C. 22.99 D. 19.67 g E. not enough information Feedback: Good. See section 8.6 Question 2 of 25 `If you ever watch a shuttle launch, you will see what looks like a crazy amount of smoke at the take off. But if you get up4.0 Points closer to the launch pad afterwards, you will see a bunch of ice! The reason is because hydrogen gas is the fuel, and it is being combusted with oxygen gas to form water: 2H2 + O2 → 2H2O. We will learn later why ice forms here even though it is so warm. But for now, what would be the total mass in grams of water (ice) if you completely combusted 200.0 kilograms of hydrogen gas? NOTE: All numbers located immediately after elemental symbols should be considered subscripts. A. 1784 kg B. 1802 kg C. 3604 kg D. 200.0 kg E. not enough information Feedback: Good. See section 8.6 Question 3 of 25 `Let's just consider the concept of stoichiometry without any confusing chemicals. Here is a generic equation: 2A + 6B 4.0 Points → 3C. If you mix 4 units of A and 11 units of B, what would be the theoretical yield of C? A. 8 B. 3 C. 6 D. 5.5 E. none of the above Feedback: Good. See section 8.5 Question 4 of 25 `Sodium and chlorine are very dangerous by themselves. However, when we combine them together in a chemical 4.0 Points reaction, we eat it--it's table salt: 2Na + Cl2 → 2NaCl. If I have 5.00 mol of chlorine gas and excess sodium, how many moles if table salt could I theoretically make? NOTE: All numbers located immediately after elemental symbols should be considered subscripts. A. 5.00 B. 10.0 C. 1.0 D. 2.00 E. not enough information Feedback: Good. See section 8.6 Question 5 of 25 `If carbon dioxide is streamed over silicon in the right conditions, you can produce solid carbon and silicon dioxide: 4.0 Points CO2 + Si → SiO2 + C. Suppose if you stream 1.50 mole of CO2 over 1.50 mole of Si. Which of the choices below represent a true statement about this reaction? NOTE: All numbers located immediately after elemental symbols should be considered subscripts. A. The CO2 is the limiting reactant. B. The SiO2 is the limiting reactant. C. You have equal stoichiometric amounts of reactants D. The Si is the limiting reactant. E. none of these are true Feedback: Good. See section 8.6 Question 6 of 25 `Magnesium oxidizes pretty easily via the reaction 2 Mg + O2 → 2 MgO. The reaction has a △H rxn = -1203 kJ. How much heat (in kJ) is released when you completely react 3.000 moles of O2? A. -401.0 kJ B. -1203 kJ C. -2406 kJ 4.0 Points D. -3609 kJ Feedback: Good. See section 8.7 Question 7 of 25 Suppose you were tasked with producing some nitrogen monoxide (a.k.a. nitric oxide). I'm sure this is often requested4.0 Points of you. You can do it by combusting ammonia (be careful!). The equation would be as follows: 4NH3 + 5O 2→ 4NO + 6H2O. If you form 2 mol of water, how much NO forms? A. 1.33 mol. B. 2.57 mol. C. 2.29 mol. D. 3.86 mol. Feedback: Good. See section 8.6 Question 8 of 25 `Determining the limiting reactant is an extremely important concept in chemistry. To do this, you need to know all of the following information EXCEPT 4.0 Points A. the molar mass of each reactant present. B. the coefficient of each reactant in a balanced equation. C. the mass of each product formed. D. the mass of each reactant present. Feedback: Good. See section 8.6 Question 9 of 25 `You have to be careful about pouring drano down your pipes since it is mainly hydrochloric acid--you can't do it if they 4.0 Points are made of aluminum because it will dissolve them! You can't acid clean your aluminum auto parts for the same reasons: 2 Al + 6 HCl → 2 AlCl3 + 3H2. If you were able to dissolve 10.0 mol of Al, how many many moles of hydrogen gas could you make? NOTE: All numbers located immediately after elemental symbols should be considered subscripts. A. 3.00 moles B. 6.00 moles C. 1.50 moles D. 15.0 moles E. none of the above Feedback: Good. See section 8.6 Question 10 of 25 `I have a buddy who recycles electronics, and isolates metals from the connector pins electrical boards. He isolates 4.0 Points gold, for example, and purifies it the best he can, then sells it along with his other scrap metal. This last go around he was able to isolate 3.00 g of Au with a process he claims results in a 80.0% yield. If he is correct, what was his theoretical yield? In other words, he got 3.00 g, but what should he have been able to get? A. 80.0 g B. 3.75 g C. 0.0375 D. 2.40 g E. none of the above Feedback: Good. See section 8.6 Question 11 of 25 `Rusting of iron is a very common chemical reaction. It results in one form from Fe reacting with oxygen gas to produce 4.0 Points iron (III) oxide. Your sample of iron is 12.0 moles of iron. So which if these is a true statement? NOTE: All numbers located immediately after elemental symbols below should be considered subscripts. A. 4.5 moles of O2 and produce 3.0 moles of Fe2O3. B. 12.0 moles of O2 and produce 24.0 moles of Fe2O3. C. 9.0 moles of O2 and produce 3.0 moles of Fe2O3. D. 9.0 moles of O2 and produce 6.0 moles of Fe2O3 E. none of the above Feedback: Good. See section 8.6 Question 12 of 25 `One way to make ammonia is to synthesize it directly from elemental nitrogen and hydrogen (though this isn't that 4.0 Points easy). The equation for this reaction would be N2 + 3 H2 → 2 NH3. If you are able to stream in 7.0 g of N2, what would be the minimum amount of H2 in grams that would be required to completely react with this amount of N2? A. 1.5 g B. 0.5 g C. 0.75 g D. 3.0 g E. none of the above Feedback: Good. See section 8.6 Question 13 of 25 `If you run a particular reaction, and in theory it was supposed to yield 50.0 grams of product, and the percent yield is 75%, how many grams did you actually end up with? A. 75.0 4.0 Points B. 37.5 C. 50.0 D. 3,750 E. none of the above Feedback: Good. See section 8.6 Question 14 of 25 `Suppose you were tasked with producing some nitrogen monoxide (a.k.a. nitric oxide). I'm sure this is often 4.0 Points requested of you. You can do it by combusting ammonia (be careful!). The equation would be as follows: 4NH3 + 5O 2→ 4NO + 6H2O. If you form 3.50 mol of water, how much NO forms? A. 2.33 mol. B. 4.00 mol. C. 4.50 mol. D. 6.75 mol. E. none of the above Feedback: Good. See section 8.6 Question 15 of 25 `Methane is also known as natural gas, and its combustion is a very common reaction: CH4 + 2 O2 → CO2 + 2 H2O. 4.0 Points Remember that we can use stoichiometry if we know the correct coefficients. So, which of these conversion factors will NOT work for this reaction? NOTE: All numbers located immediately after elemental symbols should be considered subscripts. A. 1 mole O2 = 32.00 g B. 2 mole H2O = 18.02 g C. 2 mole O2 = 1 mole CO2 D. 1 mole CH4 = 2 mole H2O E. none of the above Feedback: Good. See sections 8.3-8.4 Question 16 of 25 If you ever watch a shuttle launch, you will see what looks like a crazy amount of smoke at the take off. But if you get up 4.0 Points closer to the launch pad afterwards, you will see a bunch of ice! The reason is because hydrogen gas is the fuel, and it is being combusted with oxygen gas to form water: 2H2 + O2 → 2H2O. We will learn later why ice forms here even though it is so warm. But for now, what would be the total mass in grams of water (ice) if you completely combusted 150 kilograms of hydrogen gas? NOTE: All numbers located immediately after elemental symbols should be considered subscripts. A. 1338 kg B. 150.0 kg C. 2703 kg D. 1352 kg Feedback: Good. See section 8.6 Question 17 of 25 `Let's just consider the concept of stoichiometry without any confusing chemicals. Here is a generic equation: 2Q + 3R 4.0 Points → 3S + 4T. If you mix 5 units of Q and 7 units of R, what would be the limiting reactant? A. Q B. R C. T D. There is no limiting reactant in this situation. E. S Feedback: See section 8.5 Question 18 of 25 `N2 is fairly unreactive. However, if you can get it to react with H2, it does so in a 1:3 mole ratio (N2:H2) and releases 92.0 kJ of thermal energy. That means which if these statements are true? NOTE: All numbers located immediately after elemental symbols should be considered subscripts. A. This reaction is exothermic. B. This reaction has a negative enthalpy of reaction. 4.0 Points C. This reaction has a negative enthalpy of reaction. D. All of the above are true. E. None of the above are true. Feedback: Good. See section 8.7 Question 19 of 25 `Chemistry is not always as simple as we are learning it, of course. Many times, reactions are linked, and the products 4.0 Points of one reaction immediately become the reactants in another one. For example, 2 KClO3 → 3 O2 + 2 KCl, and then the oxygen produced goes on to make 2 Mg + O2 → 2 MgO. Suppose you begin with exactly 4 moles of potassium chlorate. If so, how much magnesium oxide can you produce? NOTE: All numbers located immediately after elemental symbols below should be considered subscripts. A. 4 moles B. 12 moles C. 6 moles D. 2 moles E. none of the above Feedback: Good. See section 8.6 Question 20 of 25 `Let's just consider the concept of stoichiometry without any confusing chemicals. Here is a generic equation: 4.0 Points 2A + 3B → C + 3D Suppose you mix 6 units of A with 8 units of B, which of these would be a true statement? 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 Feedback: Good. See section 8.5 Question 21 of 25 `Calculating your percent yield based on your amount of reactants is a very important concept in chemistry. There's a 4.0 Points little math involved, but it's something we have to be able to track for many reasons, including but not limited to cost, safety, and time. Regarding the concept of limiting reactant and percent yield, which of these choices are NOT true? A. percent yield = (actual yield / theoretical yield) × 100% B. The theoretical yield is the amount of product that can be made based on the amount of limiting reactant. C. The limiting reactant is completely consumed in a chemical reaction. D. The actual yield is the amount of product actually produced by a chemical reaction. E. All of the above are true statements. Feedback: Good. See section 8.6 Question 22 of 25 `As much as we would like for it to be the case, we never get all I the product we are supposed to get when we run a 4.0 Points real reaction. Suppose you have a theoretical yield of a 50.0 grams of product. However, your actual yield is only 32.0 g. What is your percent yield? A. 1.56% B. 64.0% C. 0.64% D. 32.0% Feedback: Good. See section 8.6 Question 23 of 25 `If you are looking to make a ginormous explosion, just drop some elemental cesium into water: Cs + 2H2O → 4.0 Points Cs(OH)2 + H2. If you are looking to make a big boom and want to produce 200.0 mol of hydrogen gas, how many moles of Cs would you need? NOTE: All numbers located immediately after elemental symbols should be considered subscripts. A. 200 B. 400 C. 100 D. 50 Feedback: Good. See section 8.6 Question 24 of 25 `Most metals are very reactive, as are the elements in the halogen group. Aluminum, for instance, For example, reacts with elemental chlorine to form aluminum chloride. If you have a 13.5 g sample of Al, which choice below is true? A. you will need 23.6 g Cl2 for complete reaction and will produce 66.7 g of AlCl3. 4.0 Points 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 Feedback: Good. See section 8.6 Question 25 of 25 `Here is one way to produce methanol: CO + 2 H2 → CH3OH . This reaction has a △H rxn = -128 kJ. How much heat (in kJ) is released when you completely react 4.04 g CO? A. -517 kJ B. -128 kJ C. -14,500 kJ 4.0 Points D. -18.5 kJ E. none of the above Feedback: Good. See section 8.7 Mobile View Powered by Sakai Copyright The Apereo Foundation. All rights reserved. Portions of Sakai are copyrighted by other parties as described in the Acknowledgments screen.