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Balloons like the one shown float in air when filled with a gas less dense than air - Leaving Cert Chemistry - Question b - 2019
Question b
Balloons like the one shown float in air when filled with a gas less dense than air. Such balloons contain a very large number of molecules when inflated. The gas mo... show full transcript
Worked Solution & Example Answer:Balloons like the one shown float in air when filled with a gas less dense than air - Leaving Cert Chemistry - Question b - 2019
Step 1
If the volume of an inflated balloon is 22.4 litres at s.t.p., how many molecules of gas does it contain?
Answer
To find the number of molecules in the balloon, we use the ideal gas law relations. At standard temperature and pressure (s.t.p.), one mole of gas occupies 22.4 litres. Therefore, if the balloon is filled with 22.4 litres, it contains:
Number of moles = [ \text{Number of moles} = \frac{22.4 \text{ litres}}{22.4 \text{ litres/mole}} = 1 \text{ mole} ]
Using Avogadro's number, which is approximately ( 6.022 \times 10^{23} \text{ molecules/mole} ), the number of molecules is:
[ \text{Number of molecules} = 1 \text{ mole} \times 6.022 \times 10^{23} \text{ molecules/mole} = 6.022 \times 10^{23} \text{ molecules} ]
Thus, the answer is ( 6 \times 10^{23} \text{ molecules} ).
Step 2
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Step 5
Which one of these gases is chemically unreactive? Explain why this gas is chemically unreactive.
Answer
The chemically unreactive gas is helium. Helium is chemically unreactive because it has a stable electron arrangement or configuration. Helium is a noble (inert) gas, which means it does not easily form chemical bonds due to having a full outer shell of electrons.
Step 6
Suggest a reason why the balloon shown in the diagram should not be filled with either of the other two gases.
Answer
The balloon should not be filled with either hydrogen or methane due to safety concerns. Both gases are flammable, making them dangerous in the presence of an ignition source. Methane is also explosive in certain concentrations in the air.