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Questions and Answers
What is the difference between mass and weight?
What is the difference between mass and weight?
Mass is the amount of matter in a material, while weight is a measure of how the force of gravity acts upon that mass.
What is the formula for calculating weight?
What is the formula for calculating weight?
W = m x g
What does the atomic mass of an element indicate?
What does the atomic mass of an element indicate?
The atomic mass of an element indicates how heavy an atom of that element is compared to an atom of another element.
What is the formula mass of a compound?
What is the formula mass of a compound?
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What is the molecular mass of ethanol, given its condensed structural formula is CH3CH2OH?
What is the molecular mass of ethanol, given its condensed structural formula is CH3CH2OH?
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What is the molecular mass of trichloromethane (Freon-11), given its condensed structural formula is CCl3F?
What is the molecular mass of trichloromethane (Freon-11), given its condensed structural formula is CCl3F?
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What is the formula for determining the mass of an element?
What is the formula for determining the mass of an element?
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What is the formula for determining the mass of an ionic compound?
What is the formula for determining the mass of an ionic compound?
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What is the formula for determining the mass of a molecular compound?
What is the formula for determining the mass of a molecular compound?
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What is the formula for determining the number of moles of an element?
What is the formula for determining the number of moles of an element?
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What is the formula for determining the number of moles of an ionic compound?
What is the formula for determining the number of moles of an ionic compound?
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What is the formula for determining the number of moles of a molecular compound?
What is the formula for determining the number of moles of a molecular compound?
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What is the formula for determining the gram (g)/mole of a substance?
What is the formula for determining the gram (g)/mole of a substance?
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What is the formula for determining the atomic mass of an element?
What is the formula for determining the atomic mass of an element?
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What is the formula for determining the formula mass of a compound?
What is the formula for determining the formula mass of a compound?
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When a new chemical compound is synthesized, chemists determine its ______ composition and ______ formula.
When a new chemical compound is synthesized, chemists determine its ______ composition and ______ formula.
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What are the percentages of carbon, hydrogen, and oxygen in sucrose (C12H22O11)?
What are the percentages of carbon, hydrogen, and oxygen in sucrose (C12H22O11)?
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What is the empirical formula of an unknown tablet that contains 40.92% C, 4.58% H, and 54.50% O by mass, and has a molecular mass of 176 g/mole?
What is the empirical formula of an unknown tablet that contains 40.92% C, 4.58% H, and 54.50% O by mass, and has a molecular mass of 176 g/mole?
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What is the formula and name of the compound that contains 33% sodium, 36% arsenic, and 31% oxygen?
What is the formula and name of the compound that contains 33% sodium, 36% arsenic, and 31% oxygen?
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What is the empirical formula of a colorless, pungent gaseous compound containing only sulfur and oxygen, if a 1.078 g sample contains 0.540 g of S and 0.538 g of O?
What is the empirical formula of a colorless, pungent gaseous compound containing only sulfur and oxygen, if a 1.078 g sample contains 0.540 g of S and 0.538 g of O?
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What is the molecular formula of benzene, given its empirical formula is CH and its molecular mass is 78 g/mole?
What is the molecular formula of benzene, given its empirical formula is CH and its molecular mass is 78 g/mole?
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What is the empirical formula of a compound containing 83% rubidium, 16% oxygen, and 1% hydrogen?
What is the empirical formula of a compound containing 83% rubidium, 16% oxygen, and 1% hydrogen?
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What is the empirical formula of a compound if a sample contains 0.130 g of nitrogen and 0.370 g of oxygen?
What is the empirical formula of a compound if a sample contains 0.130 g of nitrogen and 0.370 g of oxygen?
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What is the molecular formula of cyclobutane, given its empirical formula is CH2 and its molar mass is 42 g?
What is the molecular formula of cyclobutane, given its empirical formula is CH2 and its molar mass is 42 g?
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What are the percentages of each element in Pendimethalin (C13H19N3O4)?
What are the percentages of each element in Pendimethalin (C13H19N3O4)?
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What is the formula and name of the unknown chemical compound containing 14.39% calcium, 39.57% manganese, and 46.04% oxygen?
What is the formula and name of the unknown chemical compound containing 14.39% calcium, 39.57% manganese, and 46.04% oxygen?
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What is the law of definite proportions?
What is the law of definite proportions?
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Study Notes
Stoichiometry Part 1
- Mass vs. Weight: Mass is the amount of matter in an object, while weight is the force of gravity acting on that mass (W = m x g).
- Atomic Mass: The atomic mass (A) of an element compares the atom's mass to an atom of carbon-12 (12C), with a value of exactly 12 g/mol. It always has units of g/mol.
- Formula Mass: Sum of the atomic masses of all atoms in a compound's formula; commonly used for ionic compounds.
- Molecular Mass: Sum of atomic masses of all atoms in a molecule; commonly used for molecular compounds.
- Calculating Molecular Mass: Determine the number of each element's atoms, get their atomic masses from the periodic table, multiply each mass by its corresponding atom count, then add the values together.
- Example: Ethanol (C₂H₆O) has 2 carbon, 6 hydrogen, and 1 oxygen atoms. Its molecular mass is calculated using the atomic masses of Carbon (12 g/mol), Hydrogen (1 g/mol), and Oxygen (16 g/mol).
- Determining Percent Composition: To determine the percent of an element in a compound, calculate the mass of that element in the compound, divide that mass by the compound's total mass, and multiply by 100%.
- Empirical Formula: Provides the simplest whole number ratio of elements in a compound.
- Molecular Formula: Shows the actual number of atoms of each element in a molecule.
- Finding Empirical and Molecular Formulas: Methods utilizing percentages by mass, atomic masses, and experimental molecular masses are necessary.
- Example Problems: Illustrative examples for determining empirical formulas involve percentage data of elements. Similarly, determining molecular formulas is based on experimentally determined molecular masses.
Law of Definite Proportions
- A chemical compound consistently contains the same proportion of elements by mass. Percentage composition is constant for a pure substance.
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Description
This quiz covers the fundamentals of stoichiometry including the distinction between mass and weight, and the concepts of atomic mass, formula mass, and molecular mass. You will learn how to calculate molecular mass and determine percent composition using examples like ethanol. Test your knowledge and understanding of these essential chemistry concepts.
