I think the answer is white sand (sorry if i am wrong)
Cooler water molecules are denser than warm water and will not allow much of the salt to dissolve
Answer:

Explanation:
A pressure of 1 atm and a temperature of 0 °C is the old definition of STP. Under these conditions, 1 mol of a gas occupies 22.4 L.
1. Calculate the moles of hydrogen.

2. Calculate the number of molecules

Can you take picture of the whole question? I can’t see.