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Chemistry Chapter: Moles and Molar Mass

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Questions and Answers

What is the relationship between the molar mass and the molecular mass of a compound?

They are numerically equal. (correct)

They are numerically different quantities.

The molecular mass is used to calculate the molar mass.

The molar mass is always greater than the molecular mass.

If a scientist has 10.00 g of carbon, how many moles of carbon does this represent?

1.00 mol

0.8326 mol (correct)

12.01 mol

0.5000 mol

What is the mass of 0.905 moles of sodium chloride (NaCl)?

52.9 g (correct)

10.85 g

65.00 g

58.44 g

How many water molecules are in 3.26 g of water?

1.09 × 10²³ molecules Signup and view all the answers

What is the empirical formula of a compound that is 30.45 percent nitrogen and 69.55 percent oxygen by mass?

NO Signup and view all the answers

What is the mass of 7.92 × 10¹⁹ molecules of carbon dioxide (CO₂)?

5.79 g Signup and view all the answers

How is the molar mass of a compound calculated from its empirical formula?

By summing the atomic masses of each element in the formula. Signup and view all the answers

What is the molar mass of oxygen used in calculating the empirical formula?

16.00 g/mol Signup and view all the answers

What is the value of Avogadro's number?

6.022 × 10^23 Signup and view all the answers

How many grams are in one mole of carbon-12?

12 g Signup and view all the answers

If a body contains 30 moles of calcium, how many calcium atoms does it contain?

1.807 × 10^23 atoms Signup and view all the answers

What is the molar mass of sodium, in grams per mole?

22.99 g/mol Signup and view all the answers

How many moles are present in a sample containing 1.00 × 10^20 calcium atoms?

1.66 × 10^4 mol Signup and view all the answers

Which of the following correctly describes the relationship between atomic mass and molar mass?

Atomic mass in amu equals molar mass in grams. Signup and view all the answers

What is the number of objects in a mole?

6.022 × 10^23 objects Signup and view all the answers

The atomic mass of calcium is approximately how many amu?

40.08 amu Signup and view all the answers

Study Notes

The Mole

A mole is a unit of measurement that counts the number of particles in a substance.
A mole is defined as the number of atoms in exactly 12 g of carbon-12.
Avogadro's number (NA) represents the number of atoms in a mole, which is 6.0221418 × 10^23.

Molar Mass

Molar mass (M) refers to the mass in grams of one mole of a substance. It is measured in g/mol.
The molar mass of carbon-12 is exactly 12 g/mol.
An element's molar mass in grams is numerically equal to its atomic mass in atomic mass units (amu).
The molar mass of a compound is numerically equal to its molecular or formula mass in amu.

Interconverting Mass, Moles, and Numbers of Particles

You can calculate the number of moles of a substance by dividing the mass by its molar mass.
You can calculate the mass of a substance by multiplying the number of moles by its molar mass.
You can calculate the number of particles in a substance by multiplying the number of moles by Avogadro's number.

Empirical Formula from Percent Composition

The empirical formula represents the simplest whole-number ratio of atoms in a compound.
The percent composition of a compound can be used to determine its empirical formula.
To determine the empirical formula, assume a 100-g sample and convert the mass percentages of each element to moles.
The mole ratios of the elements will then give you the empirical formula.

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Description

Test your understanding of moles and molar mass with this interactive quiz. Explore concepts like Avogadro's number and how to interconvert mass, moles, and the number of particles in a substance. Perfect for students learning foundational chemistry principles.