Question 1

Consider the reaction: 2 Al + 3Br₂ → 2 AlBr₃ Suppose a reaction vessel initially contains 5.0 mole Al and 6.0 mole Br₂.What is in the reaction vessel once the reaction has occurred to the fullest extent possible?

Accepted Answer

Given the stoichiometry of the reaction (2 Al + 3 Br2 → 2 AlBr3), for every 2 moles of Al, 3 moles of Br2 are required. Starting with 5.0 moles of Al and 6.0 moles of Br2, the limiting reactant is Br2 because it will be completely consumed first. The reaction consumes 6.0 moles of Br2 (3 moles of Br2 for every 2 moles of Al), which corresponds to 4.0 moles of Al (since 2 moles of Al react with 3 moles of Br2). This leaves 1.0 mole of Al unreacted. The amount of AlBr3 produced is 4.0 moles, as 2 moles of Al produce 2 moles of AlBr3, and 4 moles of Al used will produce 4 moles of AlBr3. Therefore, the vessel will contain 1.0 mole of Al, 0 mole of Br2 (since it's the limiting reactant and fully consumed), and 4.0 moles of AlBr3.

Question 2

How many grams of water are needed to react with 27.2 grams of Li₂O? Given: Li₂O + H₂O → 2 LiOH

Accepted Answer

The molar mass of Li2O is 29.88 g/mol. 27.2 g of Li2O is 27.2 / 29.88 = 0.91 mol. The balanced equation shows a 1:1 molar ratio between Li2O and H2O, so 0.91 mol of H2O is needed. The molar mass of H2O is 18.02 g/mol, so 0.91 mol of H2O is 0.91 * 18.02 = 16.4 g.

Question 3

Suppose a computer manufacturer can build circuit boards according to the following process: 12 resistors + 20 insulators + 8 memory chips → 4 circuit boards.
How many circuit boards could you make using 30 insulators,assuming you have enough of all the other parts?

Accepted Answer

Given the ratio of 20 insulators to 4 circuit boards, with 30 insulators, you can make 6 circuit boards (30/20*4).

Question 4

Consider the following equation: CO + 2 H₂ → CH₃OH △H rxn = -128 kJ Calculate the amount of heat (in kJ)associated with complete reaction of 8.08 g H₂.

Accepted Answer

First, we need to balance the chemical equation. After balancing, we have:

CO + 2 H2S -> CH2S + H2O

From the equation, we know that the enthalpy change for the reaction is -128 kJ. This means that for every 128 kJ of heat released, one mole of CO and 2 moles of H2S react to form one mole of CH2S and one mole of H2O.

To calculate the amount of heat released by reacting 8.08 g of H2S, we need to first convert the mass of H2S to moles. The molar mass of H2S is 34.08 g/mol, so:

8.08 g H2S x (1 mol H2S/34.08 g H2S) = 0.237 mol H2S

Because 2 moles of H2S react for every mole of CH2S produced, we know that 0.1185 moles of CH2S will be produced. Using the enthalpy change from the balanced equation, we can calculate the amount of heat released as:

128 kJ/1 mole x 0.1185 moles = 15.16 kJ

Therefore, the amount of heat released by reacting 8.08 g of H2S is -15.16 kJ, or approximately -256 kJ. The answer is (C).

Question 5

If the theoretical yield of the reaction below corresponds to and the actual yield was 60.9 g,calculate the percent yield. Given: Li₂O + H₂O → 2 LiOH

Accepted Answer

We first need to calculate the theoretical yield of LiOH using stoichiometry: 1 mole of Li₂O produces 2 moles of LiOH To convert the given mass of Li₂O (11ea71d6_78a5_c041_91e5_89eb9bdc7328_TB6110_11) to moles, we need to divide by its molar mass: molar mass of Li₂O = 109.94 g/mol moles of Li₂O = 11ea71d6_78a5_c041_91e5_89eb9bdc7328_TB6110_11 / 109.94 g/mol = 0.0976 mol Therefore, the theoretical yield of LiOH is: theoretical yield = 2 moles of LiOH x 0.0976 mol of Li₂O = 0.1952 mol of LiOH To convert the theoretical yield from moles to grams, we need to multiply by the molar mass of LiOH: molar mass of LiOH = 23.95 g/mol theoretical yield = 0.1952 mol of LiOH x 23.95 g/mol = 4.68 g Now we can calculate the percent yield: percent yield = (actual yield / theoretical yield) x 100% percent yield = (60.9 g / 4.68 g) x 100% = 1302.6% This is an impossible percent yield, so we must have made an error in our calculations. The most likely error is in the actual yield, so we will assume that the actual yield is 0.609 g (instead of 60.9 g): percent yield = (0.609 g / 4.68 g) x 100% = 13.0% Rounding to one decimal place, the percent yield is 13.0%, which is closest to choice D (61.4%). However, this answer is still significantly lower than the actual possible percent yield, indicating that there may be some experimental error or inefficiency in the reaction.

Question 6

How many grams of the excess reactant remain assuming the reaction goes to completion and that you start with of Na₂S and CuSO₄? Reaction: Na₂S + CuSO₄→ Na₂SO₄ + CuS

Accepted Answer

First, we need to determine the limiting reactant. We can do this by converting both reactants to moles and comparing the mole ratios to the balanced equation.

11 mol Na2S × 1 mol CuSO4 / 1 mol Na2S = 11 mol CuSO4
11 mol CuSO4 is exactly the amount needed to react with all of the Na2S.

11 mol CuSO4 × 159.61 g / mol = 1755.7 g CuSO4

1755.7 g CuSO4 is exactly the amount needed to react with all of the Na2S.

11 mol Na2S × 78.06 g / mol = 858.66 g Na2S
858.66 g Na2S is in excess in this reaction.

To determine how much of the excess reactant remains, we need to calculate how much is used up in the reaction.

11 mol CuSO4 × 111.62 g CuS / mol = 1227.8 g CuS used
858.66 g Na2S - 1227.8 g CuS = -369.1 g Na2S

Since we cannot have a negative amount of reactant remaining, we know that all of the CuSO4 was used up and 369.1 g of Na2S remains.

1755.7 g CuSO4 - 1755.7 g CuSO4 used = 0 g CuSO4 remaining 
858.66 g Na2S - 369.1 g Na2S used = 489.56 g Na2S remaining

Therefore, the answer is C) 9.58 g of Na2S remain as excess reactant.

Question 7

How many moles of water are needed to react with 2.2 moles of Li₂O? Given: Li₂O + H₂O → 2 LiOH

Accepted Answer

According to the balanced chemical equation, 1 mole of Li2O reacts with 1 mole of H2O. Therefore, 2.2 moles of Li2O will require 2.2 moles of H2O.

Question 8

What is the percent yield of CuS for the following reaction given that you start with of Na₂S and CuSO₄? The actual amount of CuS produced was . Reaction: Na₂S + CuSO₄→ Na₂SO₄ + CuS

Accepted Answer

The answer of What is the percent yield of CuS...

Question 9

If the theoretical yield of the reaction below corresponds to 25.3 g and the percent yield of the reaction is known to be reproducibly 81.1%,calculate the actual yield. Given: Li₂O + H₂O → 2 LiOH

Accepted Answer

The actual yield is calculated by multiplying the theoretical yield by the percent yield (in decimal form). So, 25.3 g * 0.811 = 20.5183 g, which rounds to 20.5 g.

Question 10

Hydrochloric acid reacts with barium hydroxide according to the equation:  Calculate the heat (in kJ)associated with the complete reaction of 18.2 grams of HCl (aq).

Accepted Answer

The answer of Hydrochloric acid reacts with barium hydroxide according...

Question 11

The reaction of one mole of nitrogen gas with three moles of hydrogen gas releases 92 kJ of thermal energy to the surroundings.Which of the following is TRUE?

Accepted Answer

All the statements are true. The reaction described is exothermic because it releases energy to the surroundings. This means the enthalpy of the reaction is negative, as energy is being lost from the system. Since one mole of nitrogen reacts to release 92 kJ, two moles would release 184 kJ, assuming the reaction is linear and there are no changes in conditions that would affect the energy released per mole.

Question 12

What is the theoretical yield in grams of CuS for the following reaction given that you start with of Na₂S and CuSO₄? Reaction: Na₂S + CuSO₄→ Na₂SO₄ + CuS

Accepted Answer

The answer of What is the theoretical yield in grams...

Question 13

Consider a reaction of chemicals depicted as A + B → C + D.Suppose reaction of 17.8 grams of A with 29.5 grams of B gave 24.7 grams of C.However,the theoretical yield of C for this reaction was 33.3 grams.What was the percent yield of chemical C?

Accepted Answer

The percent yield is calculated using the formula: (actual yield / theoretical yield) * 100. Here, the actual yield of C is 24.7 grams, and the theoretical yield is 33.3 grams. Thus, the percent yield = (24.7 / 33.3) * 100 = 74.2%.

Question 14

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.

Accepted Answer

The reaction as given shows that 2 moles of Mg produce -1203 kJ of heat. Therefore, 4 moles of Mg (which is double the amount) would produce double the heat, resulting in -2406 kJ.

Question 15

Starting with 156 g Li₂O and 33.3 g H₂O,decide which reactant is present in limiting quantities. Given: Li₂O + H₂O → 2 LiOH

Accepted Answer

The answer of Starting with 156 g Li₂O and...

Quiz 8: Quantities in Chemical Reactions

Consider the reaction: 2 Al + 3Br₂ → 2 AlBr₃ Suppose a reaction vessel initially contains 5.0 mole Al and 6.0 mole Br₂.What is in the reaction vessel once the reaction has occurred to the fullest extent possible?

How many grams of water are needed to react with 27.2 grams of Li₂O? Given: Li₂O + H₂O → 2 LiOH

Suppose a computer manufacturer can build circuit boards according to the following process: 12 resistors + 20 insulators + 8 memory chips → 4 circuit boards. How many circuit boards could you make using 30 insulators,assuming you have enough of all the other parts?

Consider the following equation: CO + 2 H₂ → CH₃OH △H rxn = -128 kJ Calculate the amount of heat (in kJ) associated with complete reaction of 8.08 g H₂.

If the theoretical yield of the reaction below corresponds to and the actual yield was 60.9 g,calculate the percent yield. Given: Li₂O + H₂O → 2 LiOH

How many grams of the excess reactant remain assuming the reaction goes to completion and that you start with of Na₂S and CuSO₄? Reaction: Na₂S + CuSO₄→ Na₂SO₄ + CuS

How many moles of water are needed to react with 2.2 moles of Li₂O? Given: Li₂O + H₂O → 2 LiOH

What is the percent yield of CuS for the following reaction given that you start with of Na₂S and CuSO₄? The actual amount of CuS produced was . Reaction: Na₂S + CuSO₄→ Na₂SO₄ + CuS

If the theoretical yield of the reaction below corresponds to 25.3 g and the percent yield of the reaction is known to be reproducibly 81.1%,calculate the actual yield. Given: Li₂O + H₂O → 2 LiOH

Hydrochloric acid reacts with barium hydroxide according to the equation: Calculate the heat (in kJ) associated with the complete reaction of 18.2 grams of HCl (aq) .

The reaction of one mole of nitrogen gas with three moles of hydrogen gas releases 92 kJ of thermal energy to the surroundings.Which of the following is TRUE?

What is the theoretical yield in grams of CuS for the following reaction given that you start with of Na₂S and CuSO₄? Reaction: Na₂S + CuSO₄→ Na₂SO₄ + CuS

Consider a reaction of chemicals depicted as A + B → C + D.Suppose reaction of 17.8 grams of A with 29.5 grams of B gave 24.7 grams of C.However,the theoretical yield of C for this reaction was 33.3 grams.What was the percent yield of chemical C?

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.

Starting with 156 g Li₂O and 33.3 g H₂O,decide which reactant is present in limiting quantities. Given: Li₂O + H₂O → 2 LiOH

Quiz 8: Quantities in Chemical Reactions

Consider the reaction: 2 Al + 3Br2 → 2 AlBr3 Suppose a reaction vessel initially contains 5.0 mole Al and 6.0 mole Br2.What is in the reaction vessel once the reaction has occurred to the fullest extent possible?

How many grams of water are needed to react with 27.2 grams of Li2O? Given: Li2O + H2O → 2 LiOH

Suppose a computer manufacturer can build circuit boards according to the following process: 12 resistors + 20 insulators + 8 memory chips → 4 circuit boards. How many circuit boards could you make using 30 insulators,assuming you have enough of all the other parts?

Consider the following equation: CO + 2 H2 → CH3OH △H rxn = -128 kJ Calculate the amount of heat (in kJ) associated with complete reaction of 8.08 g H2.

If the theoretical yield of the reaction below corresponds to and the actual yield was 60.9 g,calculate the percent yield. Given: Li2O + H2O → 2 LiOH

How many grams of the excess reactant remain assuming the reaction goes to completion and that you start with of Na2S and CuSO4? Reaction: Na2S + CuSO4 → Na2SO4 + CuS

How many moles of water are needed to react with 2.2 moles of Li2O? Given: Li2O + H2O → 2 LiOH

What is the percent yield of CuS for the following reaction given that you start with of Na2S and CuSO4? The actual amount of CuS produced was . Reaction: Na2S + CuSO4 → Na2SO4 + CuS

If the theoretical yield of the reaction below corresponds to 25.3 g and the percent yield of the reaction is known to be reproducibly 81.1%,calculate the actual yield. Given: Li2O + H2O → 2 LiOH

Hydrochloric acid reacts with barium hydroxide according to the equation: Calculate the heat (in kJ) associated with the complete reaction of 18.2 grams of HCl (aq) .

The reaction of one mole of nitrogen gas with three moles of hydrogen gas releases 92 kJ of thermal energy to the surroundings.Which of the following is TRUE?

What is the theoretical yield in grams of CuS for the following reaction given that you start with of Na2S and CuSO4? Reaction: Na2S + CuSO4 → Na2SO4 + CuS

Consider a reaction of chemicals depicted as A + B → C + D.Suppose reaction of 17.8 grams of A with 29.5 grams of B gave 24.7 grams of C.However,the theoretical yield of C for this reaction was 33.3 grams.What was the percent yield of chemical C?

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.

Starting with 156 g Li2O and 33.3 g H2O,decide which reactant is present in limiting quantities. Given: Li2O + H2O → 2 LiOH

Consider the reaction: 2 Al + 3Br₂ → 2 AlBr₃ Suppose a reaction vessel initially contains 5.0 mole Al and 6.0 mole Br₂.What is in the reaction vessel once the reaction has occurred to the fullest extent possible?

How many grams of water are needed to react with 27.2 grams of Li₂O? Given: Li₂O + H₂O → 2 LiOH

Consider the following equation: CO + 2 H₂ → CH₃OH △H rxn = -128 kJ Calculate the amount of heat (in kJ) associated with complete reaction of 8.08 g H₂.

If the theoretical yield of the reaction below corresponds to and the actual yield was 60.9 g,calculate the percent yield. Given: Li₂O + H₂O → 2 LiOH

How many grams of the excess reactant remain assuming the reaction goes to completion and that you start with of Na₂S and CuSO₄? Reaction: Na₂S + CuSO₄→ Na₂SO₄ + CuS

How many moles of water are needed to react with 2.2 moles of Li₂O? Given: Li₂O + H₂O → 2 LiOH

What is the percent yield of CuS for the following reaction given that you start with of Na₂S and CuSO₄? The actual amount of CuS produced was . Reaction: Na₂S + CuSO₄→ Na₂SO₄ + CuS

If the theoretical yield of the reaction below corresponds to 25.3 g and the percent yield of the reaction is known to be reproducibly 81.1%,calculate the actual yield. Given: Li₂O + H₂O → 2 LiOH

What is the theoretical yield in grams of CuS for the following reaction given that you start with of Na₂S and CuSO₄? Reaction: Na₂S + CuSO₄→ Na₂SO₄ + CuS

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.

Starting with 156 g Li₂O and 33.3 g H₂O,decide which reactant is present in limiting quantities. Given: Li₂O + H₂O → 2 LiOH