Week 5 Lesson Quiz

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Question #1

What is the absorbance if you measure the potassium dichromate on the preset conditions at 392 nm and 100 μM?

A 0.51

B 0.37

C 0.47

D 0.72

Question #2

What is the absorbance if you measure the copper (II) sulfate on the preset conditions at 780 nm and 100 mM?

A 0.48

B 0.2

C 0.53

D 0.96

Question #3

What is the transmittance if you measure the drink mix on the preset conditions at 508 nm and 100 mM?

A 18.92%

B 31.19%

C 33.73%

D 42.69%

Question #4

What is the absorbance if you measure the potassium permanganate on the preset conditions at 544 nm and 100 μM?

A 0.48

B 0.53

C 0.96

D 0.2

Question #5

What is the transmittance if you measure the potassium permanganate on the preset conditions at 544 nm and 100 μM?

A 33.34%

B 29.44%

C 63.14%

D 10.94%

Question #6

How many significant figures does 0.005 have?

A 4

B 2

C 3

D 1

Question #7

What does accuracy refer to when discussing data measurement?

A How close a measured value is from a standard or established value

B How close a measured value is to previous measured values

C Whether or not a measurement was performed correctly

D The number of significant digits in the final measurement

Question #8

How many significant figures does 0.105 have?

A 1

B 3

C 4

D 2

Question #9

N2 is non-reactive, 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?

A This reaction is exothermic.

B This reaction has a negative enthalpy of reaction.

C This reaction has a negative enthalpy of reaction.

D All of the above are true.

Question #10

Methanol is an ingredient in windshield washer fluid and ingesting as little as 4 mL can cause blindness in humans. In the reaction below, methanol is produced from carbon dioxide and hydrogen gas. If the reaction has a △H rxn = -128 kJ, how much heat is released when 16.8 g CO is reacted? CO + 2 H2 → CH3OH

A -0.600 kJ

B -128 kJ

C -16.8 kJ

D -76.8 kJ

Question #11

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 37.5

B 3,750

C 75

D 50

E none of the above

Question #12

Sodium and chlorine are very dangerous by themselves. However, when we combine them together in a chemical 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 5.0

B not enough information

C 1.0

D 2.0

E 10.0

Question #13

Calculating your percent yield based on your amount of reactants is a very important concept in chemistry. There’s a 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 The actual yield is the amount of product actually produced by a chemical reaction.

B percent yield = (actual yield / theoretical yield) × 100%

C The limiting reactant is completely consumed in a chemical reaction.

D The theoretical yield is the amount of product that can be made based on the amount of limiting reactant.

E All of the above are true statements.

Question #14

Milk of magnesia (Maalox) contains magnesium hydroxide. Magnesium hydroxide can be reacted with hydrochloric acid to form magnesium chloride and water, as seen in the reaction below. Using this reaction, how many grams of hydrochloric acid are needed to fully react 355g magnesium hydroxide? Mg(OH)2 + 2HCl –> MgCl2 + 2H2O

A 284g

B 443g

C 142g

D 221g

Question #15

Propane is commonly used to heat gas grills. Using the balanced equation below and stoichiometry, which of the following is FALSE? C3H8 + 5O2 → 3CO2 + 4H2O

A 5 moles O2 = 4 moles H2O

B 5 moles O2 = 2 moles CO2

C 4 moles H2O = 72.08 g

D 1 mole O2 = 32.00 g

E none of the above

Question #16

In chemistry, some reactions are linked to other reactions. For example, in the decomposition of potassium chlorate, oxygen and potassium chloride are produced. Then, the oxygen can react with magnesium and produce magnesium oxide. Using the reactions below, if you start with exactly 6 moles of potassium chlorate, how much magnesium oxide can you produce? 2 KClO3 → 3 O2 + 2 KCl 2 Mg + O2 → 2 MgO

A 5 moles

B 2 moles

C 6 moles

D 18 moles

Question #17

To determine the limiting reactant in a chemical reaction, you need to know all of the following EXCEPT:

A the mass of each reactant present.

B the mass of each product formed.

C the coefficient of each reactant in a balanced equation.

D the molar mass of each reactant present.

Question #18

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.

B you will need 26.6 g Cl2 for complete reaction and will produce 49.0 g of AlCl3.

C you will need 53.2 g Cl2 for complete reaction and will produce 66.7 g of AlCl3.

D you will need 11.8 g Cl2 for complete reaction and will produce 49.0 g of AlCl3.

Question #19

Let’s just consider the concept of stoichiometry without any confusing chemicals. Here is a generic equation: 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 There is just enough of A and B so that everything reacts completely.

C Substance A will be the limiting reactant.

D Substance C cannot be formed from this reaction.

E none of the above

Question #20

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 114%

B 8.75%

C 15.00%

D 87.50%

Question #21

One way to make ammonia is to synthesize it directly from elemental nitrogen and hydrogen (though this isn’t that 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 3.0 g

B 1.5 g

C 0.75 g

D 0.5 g

E none of the above

Question #22

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 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 64.00%

B 1.56%

C 32.00%

D 0.64%

Question #23

Let’s just consider the concept of stoichiometry without any confusing chemicals. Here is a generic equation: 2Q + 3R → 3S + 4T. If you mix 5 units of Q and 7 units of R, what would be the limiting reactant?

A Q

B There is no limiting reactant in this situation.

C S

D T

E R

Question #24

If you happen to be fortunate enough to have some silver laying around the house, you are aware if its ability to tarnish. For example, elemental silver can react with hydrogen sulfide (H2S) gas in a single displacement, gas evolution reaction. Assuming there was 1.00 g of H2S floating around in the air, and you had a 2.00 g of pure silver, and there was nothing else preventing them from reacting completely, what would be the limiting reactant?

A hydrogen sulfide

B There is no limiting reactant in this case

C silver sulfide

D silver

E hydrogen

Question #25

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 12 moles of iron, if reacted completely, can produce 8 moles of iron (III) oxide.

B 9 moles of oxygen can produce 9 moles of Iron (III) oxide

C 4 moles of iron will need 2 moles of oxygen gas to fully react

D 6 moles of oxygen can react completely to produce 6 moles of iron (III) oxide.

E none of the above

Question #26

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 5

B 10

C 12

D 6

E 2

Question #27

Which of the following is NOT true regarding calculating percent yield?

A The limiting reactant is completely consumed in a chemical reaction.

B The actual yield is the amount of product actually produced by a chemical reaction

C The theoretical yield is the amount of product that can be made based on the amount of limiting reactant.

D percent yield = (actual yield / theoretical yield) × 100%

E All of the above are true statements.

Question #28

Rusting of iron is a very common chemical reaction. It results in one form from Fe reacting with oxygen gas to produce 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 9.0 moles of O2 and produce 6.0 moles of Fe2O3

B 4.5 moles of O2 and produce 3.0 moles of Fe2O3.

C 9.0 moles of O2 and produce 3.0 moles of Fe2O3.

D 12.0 moles of O2 and produce 24.0 moles of Fe2O3.

E none of the above

Question #29

`The oxidation of aluminium is a pretty commoon reaction, and happens via the equation 4Al + 3O2 → 2Al2O3. Which reactant is limiting if you begin with 5.00 grams of Al and 9.50 grams of O2?

A Al2O3

B Al

C not enough information

D O2

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