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Questions and Answers
What information is required to calculate the percent composition of an element in a compound?
What information is required to calculate the percent composition of an element in a compound?
- The density of the element and the density of the compound.
- The number of atoms of the element and the total number of atoms in the compound.
- The mass of the element in the compound and the molar mass of the compound. (correct)
- The volume of the element and the volume of the compound.
Consider a hypothetical compound $AB_2$ with a molar mass of 100 g/mol. If element A has a mass of 20g in the compound, what is the percent composition of element A?
Consider a hypothetical compound $AB_2$ with a molar mass of 100 g/mol. If element A has a mass of 20g in the compound, what is the percent composition of element A?
- 80%
- 2%
- 20% (correct)
- 50%
In iron(III) oxide ($Fe_2O_3$), if the percent composition of iron is 69.9%, what is the percent composition of oxygen?
In iron(III) oxide ($Fe_2O_3$), if the percent composition of iron is 69.9%, what is the percent composition of oxygen?
- 20.1%
- 30.1% (correct)
- 69.9%
- Cannot be determined with only this information.
A compound is found to contain 40% carbon and 6.7% hydrogen. What is the percentage of oxygen if these are the only elements present?
A compound is found to contain 40% carbon and 6.7% hydrogen. What is the percentage of oxygen if these are the only elements present?
If a compound has a molar mass of 200 g/mol and contains 40 g of element X, what is the percent composition of element X in the compound?
If a compound has a molar mass of 200 g/mol and contains 40 g of element X, what is the percent composition of element X in the compound?
What is the significance of determining the percent composition of elements in a compound?
What is the significance of determining the percent composition of elements in a compound?
Consider two compounds, $Fe_2O_3$ and $FeO$. Which statement is true regarding their percent compositions?
Consider two compounds, $Fe_2O_3$ and $FeO$. Which statement is true regarding their percent compositions?
A chemist analyzes a sample of a compound and finds that it contains 60g of carbon and 40g of oxygen. If the molar mass of the compound is 100 g/mol, what are the percent compositions of carbon and oxygen, respectively?
A chemist analyzes a sample of a compound and finds that it contains 60g of carbon and 40g of oxygen. If the molar mass of the compound is 100 g/mol, what are the percent compositions of carbon and oxygen, respectively?
When calculating the percent composition of an element in a compound, you multiply by 100. What does this multiplication represent?
When calculating the percent composition of an element in a compound, you multiply by 100. What does this multiplication represent?
If the percent composition of copper in $Cu_2S$ is approximately 79.8%, what is the percent composition of sulfur in the same compound?
If the percent composition of copper in $Cu_2S$ is approximately 79.8%, what is the percent composition of sulfur in the same compound?
A sample of a compound contains 12g of carbon, 3g of hydrogen, and 16g of oxygen. The molar mass of the compound is 31 g/mol. Which step is incorrect for determining the percent composition of carbon?
A sample of a compound contains 12g of carbon, 3g of hydrogen, and 16g of oxygen. The molar mass of the compound is 31 g/mol. Which step is incorrect for determining the percent composition of carbon?
Consider a compound with the formula $X_2Y$. If the molar mass of X is 20 g/mol and the molar mass of Y is 10 g/mol, what is the percent composition of X in the compound?
Consider a compound with the formula $X_2Y$. If the molar mass of X is 20 g/mol and the molar mass of Y is 10 g/mol, what is the percent composition of X in the compound?
A compound is composed of element A and element B. If the percent composition of element A is 65%, what can you conclude about the percent composition of element B?
A compound is composed of element A and element B. If the percent composition of element A is 65%, what can you conclude about the percent composition of element B?
Why is it important to know the molar mass of a compound when determining percent composition?
Why is it important to know the molar mass of a compound when determining percent composition?
Given a compound $XY_3$, if the percent composition of X is 40%, what is the percent composition of $Y_3$?
Given a compound $XY_3$, if the percent composition of X is 40%, what is the percent composition of $Y_3$?
A compound contains only carbon and hydrogen. If the mass of carbon is three times the mass of hydrogen, what are their approximate percent compositions?
A compound contains only carbon and hydrogen. If the mass of carbon is three times the mass of hydrogen, what are their approximate percent compositions?
What is a practical application of knowing the percent composition of compounds?
What is a practical application of knowing the percent composition of compounds?
A compound's empirical formula is CH₂O, and its molar mass is 180 g/mol. What are its percent compositions, approximately?
A compound's empirical formula is CH₂O, and its molar mass is 180 g/mol. What are its percent compositions, approximately?
How does the concept of percent composition relate to the Law of Definite Proportions?
How does the concept of percent composition relate to the Law of Definite Proportions?
If you have two different samples of the same pure compound, how would you expect their percent compositions to compare?
If you have two different samples of the same pure compound, how would you expect their percent compositions to compare?
Flashcards
Percent Composition
Percent Composition
The percentage by mass of each element in a compound.
Percent Composition Formula
Percent Composition Formula
The mass of the element in the compound divided by the molar mass of the compound, multiplied by 100.
Copper(I) Sulfide
Copper(I) Sulfide
Copper(I) sulfide is a chemical compound with the formula Cu₂S.
Molar Mass
Molar Mass
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Study Notes
- The percentage by mass of each element in a compound is known as the percent composition of the compound.
- % of element = (mass of element in compound/molar mass of compound) x 100
Sample Problem: Percent Composition
- Find the percentage composition of copper (I) sulfide, Cu₂S.
- Find the molar mass of Cu₂S: Copper (Cu₂ = 63.5 x 2 = 127.0 g) + Sulfur (S = 32.1 g) = 159.1 g
- Find the percentage by mass of each element:
- % Cu = (127.0 g / 159.1 g) x 100 = 79.8% Cu
- % S = (32.1 g / 159.1 g) x 100 = 20.2% S
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