a) synthesis- or combination- reaction
Answer:

Explanation:
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In this case, we use the Avogadro's number to compute the molecules of C2F4 whose molar mass is 100 g/mol contained in a 485-kg sample as shown below:

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The arrangement in space and the interatomic distances and angles of the atoms in crystals, usually determined by x-ray diffraction measurements
(1) The melting of a crystalline solid is best depicted by the second graph. This is because, the second graph shows a horizontal line which means that for a while there was no change in temperature. This zone is the latent heat of fusion.
(2) The first graph shows the graph of a solid that is just heated but does not experience phase change. However, the second graph shows a solid that changes phase (from crystal/solid to liquid).
So we look equation for the free Gibbs free energy (ΔG) which depends on entalpy (ΔH), temperature (T) and entropy (ΔS):
ΔG = ΔH - TΔS
ΔG is negative (-) because the water absorption on the silica gel surface is a spontaneous process.
ΔH is negative (-) because the water absorption on the silica gel surface is a exothermic process (it releases heat and if you want to desorb the water form the silica gen you need to add heat which is a endothermic process).
ΔS is negative (-) because the water is adsorbed, so from disorderly state you take the water molecules and put them in a orderly state and by doing that you decrease the entropy.