Q: Which calculation correctly determines the mass of $$\text{AlCl}_3$$ produced from 0.185 mol $$\text{Al}$$? (Molar mass $$\text{AlCl}_3 = 133.5 g/$$mol)

$$0.185 \times \frac{2}{2} \times 133.5 = 24.7 g$$

Q: A student mixes 5.0 g of $$\text{Al}$$ with 10.0 g of $$\text{Cl}_2. $$After the reaction, 2.0 g of $$\text{Al}$$ remains. What does this indicate?

$$\text{Cl}_2$$ was the limiting reagent

Q: Which of the following is the correct formula for percent yield?

$$\frac{\text{actual yield}}{\text{theoretical yield}} \times 100\%$$

Question 1

Given the reaction $$2	ext{Al}(s) + 3	ext{Cl}_2(g) ightarrow 2	ext{AlCl}_3(s)$$, how many grams of $$	ext{AlCl}_3$$ can be produced from 5.0 g of $$	ext{Al}$$ and excess $$	ext{Cl}_2$$? (Molar masses: $$	ext{Al} = 27.0 g/$$mol, $$	ext{AlCl}_3 = 133.5 g/$$mol)

Accepted Answer

$$24.7 g$$

Question 2

In the reaction $$2	ext{Al}(s) + 3	ext{Cl}_2(g) ightarrow 2	ext{AlCl}_3(s)$$, if you start with 5.0 g of $$	ext{Al}$$ and 10.0 g of $$	ext{Cl}_2$$, which reactant is the limiting reagent? (Molar masses: $$	ext{Al} = 27.0 g/$$mol, $$	ext{Cl}_2 = 70.9 g/$$mol)

Accepted Answer

$$	ext{Al}$$

Question 3

What is the theoretical yield of $$	ext{AlCl}_3 (in $$grams) when 5.0 g of $$	ext{Al}$$ reacts with 10.0 g of $$	ext{Cl}_2$$? (Molar masses: $$	ext{Al} = 27.0 g/$$mol, $$	ext{Cl}_2 = 70.9 g/$$mol, $$	ext{AlCl}_3 = 133.5 g/$$mol)

Accepted Answer

$$24.7 g$$

Question 4

If the actual yield of $$	ext{AlCl}_3 is 21.2 g$$, what is the percent yield? (Theoretical yield is 24.7 g)

Accepted Answer

$$85.8\%$$

Question 5

Which of the following best describes the concept of a limiting reagent in a chemical reaction?

Accepted Answer

The reactant that is completely consumed first, limiting the amount of product formed

Question 6

A reaction has a theoretical yield of 51.7 g and an actual yield of 45.0 g. What is the percent yield?

Accepted Answer

$$87.0\%$$

Question 7

If 35.5 g of $$	ext{Cl}_2 is $$used in the reaction $$2	ext{Al}(s) + 3	ext{Cl}_2(g) ightarrow 2	ext{AlCl}_3(s)$$, how many moles of $$	ext{Cl}_2$$ are present? (Molar mass $$	ext{Cl}_2 = 70.9 g/$$mol)

Accepted Answer

$$0.500$$ 	ext{mol}

Question 8

Which calculation correctly determines the mass of $$	ext{AlCl}_3$$ produced from 0.185 mol $$	ext{Al}$$? (Molar mass $$	ext{AlCl}_3 = 133.5 g/$$mol)

Accepted Answer

$$0.185 	imes \frac{2}{2} 	imes 133.5 = 24.7 g$$

Question 9

A student mixes 5.0 g of $$	ext{Al}$$ with 10.0 g of $$	ext{Cl}_2. $$After the reaction, 2.0 g of $$	ext{Al}$$ remains. What does this indicate?

Accepted Answer

$$	ext{Cl}_2$$ was the limiting reagent

Question 10

Which of the following is the correct formula for percent yield?

Accepted Answer

$$\frac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100\%$$

Question 11

If a reaction has a percent yield greater than 100%, what is the most likely explanation?

Accepted Answer

The product was contaminated or not completely dried

Question 12

In a laboratory, a student obtains 18.0 g of $$	ext{AlCl}_3$$ from a reaction with a theoretical yield of 24.7 g. What is the percent yield?

Accepted Answer

$$72.9\%$$

Question 13

Which step is necessary to determine the limiting reagent in a chemical reaction?

Accepted Answer

Calculate the moles of each reactant and compare their mole ratios to the balanced equation

Question 14

A reaction requires 3 moles of $$	ext{Cl}_2$$ for every 2 moles of $$	ext{Al}. If $$you have 0.185 mol $$	ext{Al}$$, how many moles of $$	ext{Cl}_2$$ are needed?

Accepted Answer

$$0.278$$ 	ext{mol}

Stoichiometry and Chemical Equation Calculations: Study Notes

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