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Weighing Gases Lesson 8PowerPoint Presentation

Weighing Gases Lesson 8

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Weighing Gases Lesson 8

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Weighing GasesLesson 8

The electrolysis of water is used to generate 0.250 g of H2 (g). If the hydrogen was generated at a rate of 1.500 amps over a period of 4.46625hours, calculate Avogadro’s number (the number of atoms of H in 1 gram)

1 amp is defined as the number of coulombs per second.

There are 6.24 x 1018 electronsin a coulomb.

It takes 1 electronto make 1 H atom

4.46625 h

x 60 min

x 60 s

x 1.500 coul

x 6.24 x 1018 el

x 1 at H

1 el

s

1 coul

1 h

1 min

= 1.505 x 1023 at H

= 6.02 x 1023 at H

0.250 g

If you weigh the volumes

1.0 L of CO2

Avogadro’s hypothesis states that equal volumes of gases have the same number of

particles.

2.56 g

=

=

=

22

0.116 g

1.0 L of H2

Note that the mass ratio is the same as the molar mass ratio

CO2

=44 g/mole

=22

H2

2.02 g/mole

A volume of an unknown gas weighs 0.563 g. An equal volume of H2 gas weighs

0.01774 g. Calculate the molar mass of the unknown gas.

Gas X

= 0.563 g

= 31.7

x 2.02 g/mole

= 64.1 g/mole

H2

0.01774g

This means the molar mass of gas X is 31.7 x heavier than H2

If the gas is a byproduct of burning coal and causes acid rain, what is the gas?

SO2

x 30.06 g/mole

= 4.02 g/mole

Gas X

= 2.365 g

= 0.1336

A volume of an unknown gas weighs 2.365g. An equal volume of C2H6 (ethane) gas

weighs 17.7g. Calculate the molar mass of the unknown gas.

C2H6

17.7 g

This means the molar mass of gas X is 0.1336 x C2H6

If the unknown gas is an element, what gas is it?

Helium

Rock me Avogadro