Chemistry: Mole Concept & Molar Mass

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Questions and Answers

At STP, how many liters does 1 mole of gas occupy?

  • 10.5 L
  • 22.4 L (correct)
  • 44.8 L
  • 15.0 L

The density of a gas can be calculated using its molar mass.

True (A)

What is the number of moles in 112 L of chlorine gas (Cl2) at STP?

5

The density of a gas is usually measured in __________.

<p>g/L</p> Signup and view all the answers

Match the gas with the number of moles that can be derived from its volume at STP:

<p>22.4 L of O2 = 1 mole 44.8 L of CO2 = 2 moles 112 L of Cl2 = 5 moles 11.2 L of H2 = 0.5 mole</p> Signup and view all the answers

How many liters does 2 moles of oxygen gas (O2) occupy at STP?

<p>44.8 L (B)</p> Signup and view all the answers

If you have 3.01 x 10^23 molecules of CO2, what is the volume at STP?

<p>22.4 L</p> Signup and view all the answers

The total number of atoms in one molecule of CO2 is three.

<p>True (A)</p> Signup and view all the answers

What is the volume occupied by 0.5 moles of O2 gas at STP?

<p>33.6 L (A)</p> Signup and view all the answers

1 mole of any gas will always occupy 22.4 liters at STP.

<p>True (A)</p> Signup and view all the answers

What is the molar mass of CO2?

<p>44 g/mol</p> Signup and view all the answers

The _______________ of a gas is directly proportional to its temperature and inversely proportional to its pressure.

<p>volume</p> Signup and view all the answers

Match the following gases with their respective molar masses:

<p>He = 4 g/mol O2 = 32 g/mol CO2 = 44 g/mol SO3 = 80 g/mol</p> Signup and view all the answers

What is the number of moles for 3.01 x 10^22 atoms of helium (He)?

<p>0.05 mol (B)</p> Signup and view all the answers

One H2SO4 molecule contains a total of 6 atoms.

<p>False (B)</p> Signup and view all the answers

What is Avogadro's number?

<p>6.02 x 10^23</p> Signup and view all the answers

If 10 moles of oxygen (O2) molecules are given, the total number of oxygen __________ present is 1.204 x 10^24.

<p>molecules</p> Signup and view all the answers

Match the following gases with their molecular formulas:

<p>Oxygen = O2 Hydrogen = H2 Sulfur Dioxide = SO2 Carbon Dioxide = CO2</p> Signup and view all the answers

How many atoms are there in 1.204 x 10^24 H2SO4 molecules?

<p>8.428 x 10^24 (C)</p> Signup and view all the answers

The total number of atoms in 2 moles of H2SO4 is 1.204 x 10^23.

<p>False (B)</p> Signup and view all the answers

Calculate the total number of oxygen atoms in 10 moles of O2.

<p>1.204 x 10^25</p> Signup and view all the answers

Flashcards

Volume of 1 mole of gas at STP

At standard temperature and pressure (STP), 1 mole of any ideal gas occupies a volume of 22.4 liters.

STP

Standard Temperature and Pressure, a set of standard conditions for comparing gases. It's 0°C and 1 atm pressure.

Moles and Volume

The volume of a gas sample is directly proportional to the number of moles of gas present, assuming constant temperature and pressure.

Calculating gas volume (moles)

The volume of a specific amount of gas (in moles) can be found if the volume of 1 mole of gas is known at standard conditions.

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Mole relationship to mass

The mass of a substance is directly proportional to the number of moles of the substance present.

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Moles of a gas at STP

At standard temperature and pressure (STP), 1 mole of any gas occupies 22.4 liters.

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Calculating moles from volume (STP)

The number of moles (n) of a gas at STP can be found using the formula: n = V / 22.4, where V is the volume in liters.

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Volume of 5 moles of Cl2 at STP

5 moles of chlorine gas (Cl2) at STP occupy 112 liters.

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Volume of 2 moles of O2 at STP

2 moles of oxygen gas (O2) occupy 44.8 liters at STP.

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Density of a gas at STP

The density of a gas at STP is usually given in grams per liter (g/L).

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Calculating number of atoms in molecules

Each molecule has a specific number of atoms. Multiply the number of moles by Avogadro's number and then by the number of atoms per molecule.

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Molar mass

The mass of one mole of a substance. Units are typically grams per mole (g/mol).

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Number of Moles Calculation

To find the number of moles of a substance, divide the number of particles (atoms, molecules, ions) by Avogadro's number (6.02 x 10^23).

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Avogadro's Number

The number of particles (atoms, molecules, ions) in one mole of a substance.

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Mole Concept

A mole represents a specific number of particles of a substance. It's a unit of measurement in chemistry.

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How many moles are in 3.01 x 10^22 helium atoms?

Divide the number of helium atoms by Avogadro's number to get the number of moles. (0.05)

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Atoms in Hâ‚‚SOâ‚„

One Hâ‚‚SOâ‚„ molecule contains 7 atoms (2 hydrogen, 1 sulfur, 4 oxygen).

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Calculate the total number of atoms in 2 moles of Hâ‚‚SOâ‚„ molecules.

Firstly, find the number of Hâ‚‚SOâ‚„ molecules in 2 moles. Then multiply by the number of atoms per molecule.

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Mole Relationship to Atoms

A mole of a substance contains Avogadro's number of that substance's atoms, ions, or molecules

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Calculate oxygen molecules in 10 moles Oâ‚‚?

Multiply the number of moles by Avogadro's number to find the number of oxygen molecules.

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Study Notes

Mole Concept

  • The mole is a fundamental unit in chemistry used to express quantities of small particles (atoms, molecules, etc.).
  • One mole is defined as 6.02 × 1023 particles.
  • Avogadro's number, represented by NA, is 6.02 × 1023.
  • The molar volume of any gas at STP (standard temperature and pressure) is 22.4 L/mol.
  • Molar mass (M) is the mass of one mole of a substance in grams.
  • The molar mass of an element is numerically equal to its atomic mass in atomic mass units (amu).
  • The molar mass of a compound is calculated by summing the atomic masses of all atoms in the compound.

Avogadro's Number

  • Avogadro's number is used to relate the number of particles to the mass or volume of a substance.
  • It allows for conversion between the number of particles, mass, and volume of a substance.
  • The relationship between grams and amu is Avogadro's number, 6.02 × 1023.

Molar Mass

  • Molar mass is the mass of one mole of a substance in grams.
  • It's used to calculate the mass of a given number of moles.
  • Calculate the molar mass of a substance by summing the atomic masses of the constituent elements.

Molar Volume of Gases

  • At STP (standard temperature and pressure), one mole of any ideal gas occupies a volume of 22.4 liters.
  • The volume of a gas at STP can be used to determine the number of moles of gas.

Mole-Mass Relationship

  • Moles can be calculated from mass using the formula: moles = mass / molar mass.
  • Mass is calculated from moles using the formula: mass = moles × molar mass.

Mole-Volume Relationship

  • Moles of a gas at STP can be calculated given its volume. The formula is: moles = volume / 22.4 L/mol,
  • The volume of any gas at STP is 22.4 L per mole.

Mixture Problems

  • Mixture problems involve calculating components of mixtures using basic mathematical operations.
  • For example, the total mass of a mixture or the number of moles of the components in a mixture might be asked.

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