Lesson test: Counting a reaction

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Counting a reaction

1.[2p]
What does a balanced chemical equation assert, and nothing more?

That atoms of each element and total charge are conserved between the two sides

Correct

That the reaction proceeds to completion as written

The answer is: That atoms of each element and total charge are conserved between the two sides

That the reaction releases energy in the direction of the arrow

The answer is: That atoms of each element and total charge are conserved between the two sides

That the reactants will react when mixed

The answer is: That atoms of each element and total charge are conserved between the two sides

2.[2p]
How many moles of are needed to burn one mole of octane, , completely to $C$ and $O$ ?

CorrectNot quite: 12.5

3.[3p]
$10.0$ g of aluminium ( $26.982$ g mol⁻¹) reacts with $35.0$ g of chlorine, $C$ ( $70.90$ g mol⁻¹), as $2 Al + 3 C \to 2 AlC$ . What mass of $AlC$ ( $133.33$ g mol⁻¹) can form, in grams?

CorrectNot quite: 43.9

4.[1p]
Since the 2019 redefinition, the Avogadro constant is an exact number rather than a measured one.

True

Correct

False

The answer is: True

5.[2p]
A vessel is charged with $5.00$ mol of $S$ and $3.00$ mol of , reacting as $2 S + \to 2 S$ . What is the largest possible extent of reaction, in moles?

CorrectNot quite: 2.50

6.[2p]
Match each species in $+ 3 \to 2 N$ to its stoichiometric number.

+2
-1
-3

Show the answer

N2: -1 H2: -3 NH3: +2

7.[2p]
Combustion analysis of a compound of C, H and O gives amounts in the ratio 1 : 2 : 1. What is its empirical formula?

CorrectNot quite: CH2O

8.[3p]
A reaction gives a percentage yield below 100. Which of these can account for it?

Select all that apply

The mixture reached equilibrium before the limiting reagent ran out

Correct

The reaction was still running when it was stopped

Correct

Some reagent was consumed by a competing side reaction

Correct

Atoms were destroyed during the reaction

The answer is: The mixture reached equilibrium before the limiting reagent ran out, The reaction was still running when it was stopped, Some reagent was consumed by a competing side reaction

9.[2p]
Balancing the reaction of carbon with oxygen, allowing both $CO$ and $C$ as products, gives more than one independent solution. What does that mean?

Conservation alone does not fix the products, which depend on the conditions

Correct

The equation is unbalanceable and must be rewritten

The answer is: Conservation alone does not fix the products, which depend on the conditions

One of the two products is impossible

The answer is: Conservation alone does not fix the products, which depend on the conditions

Charge is not conserved in the reaction

The answer is: Conservation alone does not fix the products, which depend on the conditions

1.[2p] What does a balanced chemical equation assert, and nothing more?

2.[2p] How many moles of are needed to burn one mole of octane, , completely to C and O?

3.[3p] 10.0 g of aluminium (26.982 g mol⁻¹) reacts with 35.0 g of chlorine, C (70.90 g mol⁻¹), as 2Al+3C→2AlC. What mass of AlC (133.33 g mol⁻¹) can form, in grams?

4.[1p] Since the 2019 redefinition, the Avogadro constant is an exact number rather than a measured one.

5.[2p] A vessel is charged with 5.00 mol of S and 3.00 mol of , reacting as 2S+→2S. What is the largest possible extent of reaction, in moles?

6.[2p] Match each species in +3→2N to its stoichiometric number.

7.[2p] Combustion analysis of a compound of C, H and O gives amounts in the ratio 1 : 2 : 1. What is its empirical formula?

8.[3p] A reaction gives a percentage yield below 100. Which of these can account for it?

9.[2p] Balancing the reaction of carbon with oxygen, allowing both CO and C as products, gives more than one independent solution. What does that mean?

1.[2p]
What does a balanced chemical equation assert, and nothing more?

2.[2p]
How many moles of are needed to burn one mole of octane, , completely to $C$ and $O$ ?

3.[3p]
$10.0$ g of aluminium ( $26.982$ g mol⁻¹) reacts with $35.0$ g of chlorine, $C$ ( $70.90$ g mol⁻¹), as $2 Al + 3 C \to 2 AlC$ . What mass of $AlC$ ( $133.33$ g mol⁻¹) can form, in grams?

4.[1p]
Since the 2019 redefinition, the Avogadro constant is an exact number rather than a measured one.

5.[2p]
A vessel is charged with $5.00$ mol of $S$ and $3.00$ mol of , reacting as $2 S + \to 2 S$ . What is the largest possible extent of reaction, in moles?

6.[2p]
Match each species in $+ 3 \to 2 N$ to its stoichiometric number.

7.[2p]
Combustion analysis of a compound of C, H and O gives amounts in the ratio 1 : 2 : 1. What is its empirical formula?

8.[3p]
A reaction gives a percentage yield below 100. Which of these can account for it?

9.[2p]
Balancing the reaction of carbon with oxygen, allowing both $CO$ and $C$ as products, gives more than one independent solution. What does that mean?