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In the process of photosynthesis, water and carbon dioxide are produced.

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False

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In the carbon cycle, combustion produces atmospheric oxygen.

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False

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In a balanced chemical equation, the number of each type of atom in the reactants must always equal the number of the same atom of the products.

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False

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The empirical formula for H₂O, H₂O₂, NH₃, N₂H₄, C₁₂H₂₂O₁₁, and Al₂Cl₆are H₂O, HO, NH₃, NH₂, C₁₂H₂₂O₁₁, AlCl₃, respectively.

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During the combustion reaction, a hydrocarbon reacts with oxygen to form carbon monoxide and water.

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False

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Stoichiometry of a chemical reaction refers to the quantitative relationships between the amounts of reactants and products involved in the reaction.

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The limiting reagent is the reactant that is consumed (ran out) first during the chemical reaction. The limiting reagent will dictate the amount of product being formed according the stoichiometry of a balanced chemical reaction.

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The percent composition of a compound is the number of moles of an element in the compound divided by the number of moles of the compound itself.

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The actual yield (experimentally determined) of a chemical reaction is almost always larger than the theoretical yield because of side reactions, incomplete reactions, and loss during purification steps. The percent yields for most reactions are less than 100%.

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Molecules that have the same empirical formula will have the same percent composition of a given element.

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False

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Hydrogen peroxide decomposes to produce water and oxygen according to the following reaction:

2 H₂O₂ (l) → 2 H₂O (l) + O₂ (g).

Which one of the following relationships regarding the quantities of reactants and products associated with this reaction is NOT correct?

Select one:

a. 2 molecules of H₂O₂ → 2 molecules of H₂O + 1 molecule of O₂.

b. 2 mol of H₂O₂ → 2 mol of H₂O + 1 mol of O₂.

c. 68.0 g of H₂O₂ → 36.0 g of H₂O + 32.0 g of O₂.

d. 2 g of H₂O₂ → 2 g of H₂O + 1 g of O₂.

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Air bags in cars inflate when an electrical spark activates sodium azide (NaN₃) so that it decomposes to sodium metal and nitrogen gas. In the corresponding balanced chemical equation, how many moles of N₂ gas are formed for each mole of NaN₃?

Select one:

a. 1.0

b. 1.5

c. 2.0

d. 3.0

e. 3.5

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How many moles of ammonia are there in a 346 g sample of pure NH₃ (17.03 g/mol)?

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a. 0.0496 mol.

b. 20.3 mol.

c. 24.7 mol.

d. 5930 mol.

e. 3.46 mol.

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How many moles of chlorine are in 25.0 g of calcium chloride (CaCl₂)?

Select one:

a. 0.705 mol of chlorine (Cl).

b. 0.451 mol of chlorine (Cl).

c. 0.331 mol of chlorine (Cl).

d. 0.225 mol of chlorine (Cl).

e. 0.676 mol of chlorine (Cl).

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Arizona was the site of a 400,000-acre wildfire in June 2002. Assume that the density of carbon on the acreage was 10 kg/m² and that only 50% of the biomass burned. How much carbon dioxide was produced by this fire?

[Hint: 10,000 m² = 2.47 acre.]

Select one:

a. 3 x10¹⁰ kg of CO₂.

b. 3 x10⁶ kg of CO₂.

c. 3 x10³⁰ kg of CO₂.

d. 3 x10⁹ kg of CO₂.

e. 3 x10¹³ kg of CO₂.

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Han purple, a synthetic inorganic pigment developed in China in ancient times, has the chemical formula BaCuSi₂O₆. What is the percent composition of silicon in Han purple?

Select one:

a. 18.0%.

b. 15.9%.

c. 27.2%.

d. 38.9%.

e. 7.96%.

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A hydrocarbon molecule contains twice as many hydrogen atoms as carbon atoms. Its molar mass is 84.15 g/mol. What is the molecular formula for the hydrocarbon?

Select one:

a. C₇H₁₄

b. C₆H₁₂

c. C₅H₁₀

d. C₈H₁₆

e. CH₂

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Potassium superoxide (KO₂, 71.10 g/mol) can be used to generate oxygen gas according to the following reaction:

4 KO₂ (s) + 2 H₂O (L) → 4 KOH (S) + 3 O₂ (g)

What is the theoretical yield of O₂ (32.00 g/mol) if 500.0 g KO₂ reacts with excess H₂O (18.02 g/mol)?

Select one:

a. 225.0 g

b. 168.8 g

c. 375.0 g

d. 675.1 g

e. 56.26 g

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If 98.0 g B₂O₃ (69.62 g/mol) and 125 g HF (20.01 g/mol) are combined and allowed to react according to the following chemical equation:

B₂O₃ (s) + 6 HF (aq) → 2 BF₃ (g) + 3 H₂O (l)

What mass of the excess reactant will be left over after the reaction stops?

Select one:

a. 72.5 g B₂O₃ will be left over.

b. 25.5 g B₂O₃ will be left over.

c. 28.2 g HF will be left over.

d. 7.34 g HF will be left over.

e. Both are completely consumed.

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A mass of 11.60 g of phosphoric acid (98.00 g/mol) was produced from the reaction of 10.00 g of P₄O₁₀ (283.9 g/mol) with 12.00 g water (18.02 g/mol). What was the percent yield for this reaction?

Select one:

a. 78.62%      

b. 101.1%      

c. 92.70%

d. 84.00%

e. 52.70%

Answer 1