Percent Composition and Empirical Formulas Quiz

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Questions and Answers

What is the main purpose of calculating percent composition in chemistry?

To identify the chemical structure of a substance

To determine the molecular weight of a compound

To balance a chemical equation

To find out the percentage of each element in a compound (correct)

In the compound CuBr2, bromine contributes more to the mass percent than copper.

True

What is the empirical formula for glucose, C6H12O6?

CH2O

The percent composition of nitrogen in (NH4)2S is _________.

21.2% Signup and view all the answers

Match the compounds with their percent composition by mass of nitrogen:

NH3 = 82.2% CO(NH2)2 = 40% (NH4)2SO4 = 21.2% Signup and view all the answers

Which of the following compounds has the highest percentage of mass of nitrogen?

NH3 Signup and view all the answers

The calculation of percent composition is only needed for ionic compounds.

False Signup and view all the answers

How do you determine the percent composition of a compound?

Calculate the molar mass of each element and divide it by the molar mass of the compound, then multiply by 100. Signup and view all the answers

What is the empirical formula of C6H12O6?

C3H6O3 Signup and view all the answers

An empirical formula can show the exact number of atoms of each element in a compound.

False Signup and view all the answers

What is the molecular formula of a compound with an empirical formula of C2OH4 and a molecular mass of 88 g/mol?

C4O2H8 Signup and view all the answers

A sample contains 0.3374g of P, 0.0220g of H, and the remainder is O. The empirical formula is __________.

H3PO4 Signup and view all the answers

Match the following compounds with their corresponding empirical formulas:

C2H2 = CH C8H14 = C4H7 C12H22O11 = C12H22O11 C8H18 = C4H9 Signup and view all the answers

How many moles of oxygen (O2) are needed to react with 3.24 moles of ammonia (NH3) in the reaction: _NH3 + _O2 → _NO + _H2O?

5.00 moles Signup and view all the answers

If 145.7 grams of manganese (IV) oxide (MnO2) are reacted, how many grams of hydrochloric acid (HCl) are required to completely react with it?

Requires stoichiometric calculation based on balanced reaction. Signup and view all the answers

The molar mass of lead (II) nitrate (Pb(NO3)2) is essential for calculating the grams needed to produce a given mass of sodium nitrate (NaNO3).

True Signup and view all the answers

What is the percent yield of the reaction if 75.0 g of P4 yields 111.0 g of PCl3?

65.4% Signup and view all the answers

In the reaction of Fe(OH)2 with H3PO4, both reactants will yield the same amount of product.

False Signup and view all the answers

What is the limiting reagent when 3.20 g of Fe(OH)2 reacts with 2.50 g of H3PO4?

Fe(OH)2 Signup and view all the answers

When octane (C8H18) is burned, _____ and water are produced.

carbon dioxide Signup and view all the answers

Match the following reactions with their expected yields:

P4 + 6 Cl2 → 4 PCl3 = Mass of PCl3 Fe + CuSO4 → FeSO4 + Cu = Mass of Cu C8H18 + O2 → CO2 + H2O = Mass of H2O produced Signup and view all the answers

How many grams of water can be produced from the complete combustion of 320 g of octane?

392 g Signup and view all the answers

If 98.03 g of Magnesium hydroxide decomposes, no water will be produced.

False Signup and view all the answers

How many grams of Fe3(PO4)2 precipitate can be formed from the reaction of Fe(OH)2 and H3PO4?

Calculated based on limiting reagent and stoichiometry. Signup and view all the answers

What is the empirical formula for a compound containing 18.7g of C and 6.28g of H?

C2H7 Signup and view all the answers

Multiple compounds can have different empirical formulas.

False Signup and view all the answers

What is needed to determine the true formula of a compound aside from the empirical formula?

Molar mass Signup and view all the answers

The ____ reactions tell you how many molecules and/or atoms of each reactant are needed to make the products.

chemical equations Signup and view all the answers

Match the following compounds with their respective formulas:

Sodium Oxide = Na2O Sodium Hydroxide = NaOH Sodium Phosphate = Na3PO4 Glucose = C6H12O6 Signup and view all the answers

In converting element masses to moles, what can be determined?

Empirical ratio Signup and view all the answers

The balanced chemical equation for aluminum reacting with oxygen produces aluminum chloride.

False Signup and view all the answers

If 24 atoms of aluminum are present, how many molecules of aluminum oxide will be produced?

12 molecules Signup and view all the answers

How many moles of calcium carbonate are formed when 0.50 moles of calcium oxide reacts with 0.40 moles of carbon dioxide?

0.40 moles Signup and view all the answers

The theoretical yield of ammonia (NH3) can exceed 10.5 g when 15.0 g of nitrogen gas reacts with hydrogen gas.

False Signup and view all the answers

If 0.996 g of aluminum hydroxide is recovered from a reaction involving 2.80 g of aluminum nitrate, what is the actual yield of aluminum hydroxide?

0.996 g Signup and view all the answers

To produce 30.0 g of aluminum phosphate with a % yield of 73.7%, the theoretical mass of aluminum needed is _____ g.

40.7 Signup and view all the answers

What information is crucial when calculating the percent yield of a chemical reaction?

Theoretical yield and actual yield Signup and view all the answers

Match the chemical reaction types with their appropriate description:

Combination = Two or more substances combine to form one product Decomposition = A single compound breaks down into two or more products Single Replacement = One element replaces another in a compound Double Replacement = Exchange of ions between two compounds Signup and view all the answers

The limiting reactant in a chemical reaction is always the reactant with the smallest amount in moles.

False Signup and view all the answers

What do you calculate first when determining the mass of reactants needed to produce a desired mass of products?

Theoretical yield using molar ratios Signup and view all the answers

What is the balanced chemical equation for the reaction of nitrogen and hydrogen to form ammonia?

N2 + 3H2 → 2NH3 Signup and view all the answers

The limiting reactant is the reactant that is left over after a reaction has taken place.

False Signup and view all the answers

What is percent yield?

The ratio of actual yield to theoretical yield, expressed as a percentage. Signup and view all the answers

In a chemical reaction, the full amount of product produced is called __________ yield.

theoretical Signup and view all the answers

If a student obtained 6.5 g of NH3 from the reaction of 6.0 g of N2 and 18.0 g of H2, what is the formula to calculate the percent yield?

Percent yield = (Actual yield / Theoretical yield) * 100 Signup and view all the answers

In the reaction of nitrogen and hydrogen, how do you determine the limiting reactant using masses?

By calculating the moles of each reactant and determining which one produces the least amount of product. Signup and view all the answers

Match the following terms with their definitions:

Limiting reactant = The reactant that is entirely consumed in a reaction Excess reactant = The reactant that remains after the reaction is complete Theoretical yield = The amount of product expected from a reaction under ideal conditions Actual yield = The amount of product actually obtained from a reaction Signup and view all the answers

The percent yield can be calculated using the formula: Percent yield = __________ yield / Theoretical yield * 100.

Actual Signup and view all the answers

Study Notes

Unit 7: Stoichiometry

Learning Objectives: Apply first-semester learning to convert word equations into balanced chemical equations. Include identifying ionic and covalent compounds, diatomic elements, polyatomic ions, and naming/balancing chemical equations.
Percent Composition: Calculate the percent composition of each element in a molecule.
Empirical Formula: Calculate the empirical formula of a substance using mass quantities or percent composition.
Molecular Formula: Calculate the molecular formula using mass quantities, percent composition, and molar mass.
Mole Ratios: Given balanced chemical equations, determine the theoretical yield and find the limiting reagent.
Limiting Reactant: Identify the reactant fully consumed in a reaction.
Excess Reactant: Determine the amount of reactant left over when a reaction has reached completion.
Percent Yield:
- Calculate experimentally determined actual yield vs theoretical yield
- Measure percentage using the ratio of actual yield to theoretical yield and 100 as the denominator.

Worksheet Contents

WS#1: Percent Composition
WS#2: Percentage Composition and Empirical Formula
WS#3: Reaction Stoichiometry
WS#4: Limiting and Excess Reactant Stoichiometry
WS#5: Limiting Reactant and Percent Yield Practice
WS#6: Word Equations and Stoichiometry
U7 Lecture Notes: (Pages 12-18- not graded)

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Test your knowledge on the calculation of percent composition and empirical formulas in chemistry. This quiz includes questions on compounds such as CuBr2 and glucose, and challenges you to match compounds with their corresponding mass percent of nitrogen. Dive deep into the essential concepts of chemistry related to molecular and empirical formulas.

Percent Composition and Empirical Formulas Quiz

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Questions and Answers

What is the main purpose of calculating percent composition in chemistry?

In the compound CuBr2, bromine contributes more to the mass percent than copper.

What is the empirical formula for glucose, C6H12O6?

The percent composition of nitrogen in (NH4)2S is _________.

Match the compounds with their percent composition by mass of nitrogen:

Which of the following compounds has the highest percentage of mass of nitrogen?

The calculation of percent composition is only needed for ionic compounds.

How do you determine the percent composition of a compound?

What is the empirical formula of C6H12O6?

An empirical formula can show the exact number of atoms of each element in a compound.

What is the molecular formula of a compound with an empirical formula of C2OH4 and a molecular mass of 88 g/mol?

A sample contains 0.3374g of P, 0.0220g of H, and the remainder is O. The empirical formula is __________.

Match the following compounds with their corresponding empirical formulas:

How many moles of oxygen (O2) are needed to react with 3.24 moles of ammonia (NH3) in the reaction: _NH3 + _O2 → _NO + _H2O?

If 145.7 grams of manganese (IV) oxide (MnO2) are reacted, how many grams of hydrochloric acid (HCl) are required to completely react with it?

The molar mass of lead (II) nitrate (Pb(NO3)2) is essential for calculating the grams needed to produce a given mass of sodium nitrate (NaNO3).

What is the percent yield of the reaction if 75.0 g of P4 yields 111.0 g of PCl3?

In the reaction of Fe(OH)2 with H3PO4, both reactants will yield the same amount of product.

What is the limiting reagent when 3.20 g of Fe(OH)2 reacts with 2.50 g of H3PO4?

When octane (C8H18) is burned, _____ and water are produced.

Match the following reactions with their expected yields:

How many grams of water can be produced from the complete combustion of 320 g of octane?

If 98.03 g of Magnesium hydroxide decomposes, no water will be produced.

How many grams of Fe3(PO4)2 precipitate can be formed from the reaction of Fe(OH)2 and H3PO4?

What is the empirical formula for a compound containing 18.7g of C and 6.28g of H?

Multiple compounds can have different empirical formulas.

What is needed to determine the true formula of a compound aside from the empirical formula?

The ____ reactions tell you how many molecules and/or atoms of each reactant are needed to make the products.

Match the following compounds with their respective formulas:

In converting element masses to moles, what can be determined?

The balanced chemical equation for aluminum reacting with oxygen produces aluminum chloride.

If 24 atoms of aluminum are present, how many molecules of aluminum oxide will be produced?

How many moles of calcium carbonate are formed when 0.50 moles of calcium oxide reacts with 0.40 moles of carbon dioxide?

The theoretical yield of ammonia (NH3) can exceed 10.5 g when 15.0 g of nitrogen gas reacts with hydrogen gas.

If 0.996 g of aluminum hydroxide is recovered from a reaction involving 2.80 g of aluminum nitrate, what is the actual yield of aluminum hydroxide?

To produce 30.0 g of aluminum phosphate with a % yield of 73.7%, the theoretical mass of aluminum needed is _____ g.

What information is crucial when calculating the percent yield of a chemical reaction?

Match the chemical reaction types with their appropriate description:

The limiting reactant in a chemical reaction is always the reactant with the smallest amount in moles.

What do you calculate first when determining the mass of reactants needed to produce a desired mass of products?

What is the balanced chemical equation for the reaction of nitrogen and hydrogen to form ammonia?

The limiting reactant is the reactant that is left over after a reaction has taken place.

What is percent yield?

In a chemical reaction, the full amount of product produced is called __________ yield.

If a student obtained 6.5 g of NH3 from the reaction of 6.0 g of N2 and 18.0 g of H2, what is the formula to calculate the percent yield?

In the reaction of nitrogen and hydrogen, how do you determine the limiting reactant using masses?

Match the following terms with their definitions:

The percent yield can be calculated using the formula: Percent yield = __________ yield / Theoretical yield * 100.

Study Notes

Unit 7: Stoichiometry

Worksheet Contents

Studying That Suits You

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