The Mole-Mass and Mole Volume Relationships Chemical Quantities Chapter 10 Section 2

Vocabulary • •

Avogadro’s hypothesis

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Equal volumes of gases at the same temperature and pressure contain equal numbers of particles Standard temperature and pressure (STP)

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The conditions under which the volume of a gas is usually measured; standard temperature is 0oC, and the standard pressure is 101.3 kPa, or 1 atmosphere (atm).

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Vocabulary •

Molar volume

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The volume occupied by 1 mole of a gas at standard temperature and pressure (STP); 22.4 L

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State Standards • • 5.3 Use the mole concept to determine number of particles and molar mass for elements and compounds.

5.4 Determine percent compositions, empirical formulas, and molecular formulas 4

Key Questions • • How do you convert the mass of a substance to the number of moles of the substances?

How do you convert the volume of a gas at STP to the number of moles of the gas?

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The Mole-Mass Relationship • •

Use the molar mass of an element or compound to convert between the mass of a substance and the mole of the substance

Molar mass = 1 mole 6

The Mole-Volume Relationship • Avogrado’s hypothesis – Equal volumes of gases at the same temperature and pressure contain equal number particles 7

The Mole-Volume Relationship • •

Standard Temperature and Pressure

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0 o C

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101.3 kPa or 1 atmosphere (1 atm) Molar Volume

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At STP

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One mole of gas = 22.4 L

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The Mole-Volume Relationship • •

The molar volume is used to convert between number of moles of gas and the volume of the gas at STP.

Conversion factor – 22.4 L = 1 mol at STP 9

The Mole-Volume Relationship • • • • Different gases have different densities.

Usually density is measured in g/L at a specific temperature

The density of a gas at STP and the molar volume at STP (22.4 L.mol) can be used to calculate the molar mass of the gas.

The molar mass of a gas and the molar volume at STP can be used to calculate the density of a gas at STP.

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Summary • •

Use the molar mass of an element or compound to convert between the mass of a substance and the moles of the substance.

The molar volume is used to convert between the number of moles of gas and the volume of the gas at STP.

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