From the ideal gas equation,

where n is number of moles, R is Universal gas constant, P is pressure, V is volume, and T is temperature of the gas.
The pressure and volume are inversely proportional to each other at constant temperature and number of moles.
Hence, on decreasing the pressure, the volume will increase.
As the hiker reaches a height of a mountain, the pressure would decrease which results in the reestablishment of equilibrium between gas molecules thus resulting in pushing of bag outwards.
Hence, the bag will expand as the hiker reaches the top of the mountain.
Number of moles = 8.3 x 10⁻¹³
<h3>Further explanation
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The mole is the number of particles(molecules, atoms, ions) contained in a substance
1 mol = 6.02.10²³ particles
Can be formulated
N=n x No
N = number of particles
n = mol
No = Avogadro's = 6.02.10²³
5 x 10¹¹ atoms of Silver :

Answer:The sun
Explanation:
Coal and crude oil are made from the remains of plants and animals that died long ago. The primary energy source in an ecosystem is the sun. Plants take in energy from the sun to produce high energy molecules which are transferred along the food chain to animals. When these plants and animals die, the high energy molecules are now stored in fossil fuels. Recall that the molecules were formed using energy from the sun, therefore, the sun is the energy source from which the high energy molecules contained in fossil fuels are obtained.