<h3>
Answer:</h3>
250.756 moles He
<h3>
Explanation:</h3>
From the question we are given;
Volume, L = 685 L
Temperature, T = 621 K
Pressure, P = 189 × 10 kPa
We are required to calculate the number of moles of the gas,
Using the Ideal gas equation,
PV = nRT, where P is the pressure, V is the volume, T is the temperature, n is the number of moles, and R is the ideal gas constant.
We can replace the known variables and constant in the equation to get the unknown variable, n.
Using ideal gas constant as 8.3145 L.kPa/K/mol



n = 250.756 moles
The moles of helium contained in the sphere is 250.756 moles
The lower you go, the more acidic. The higher you go, the more alkaline. Your answer would most likely be 6.
Answer: The forces of attraction are stronger in new attractions that are formed.
Explanation:
When a chemical reaction takes place between two or more different compounds then less reactive substance is displaced by the more reactive substance.
During this process, when bonds are broken between the reactants then it means the force of attraction is less stronger. The formation of new compounds occur because force of attraction is more in these new substances due to which its atoms come closer to each other.
Thus, we can conclude that forces of attraction are stronger in new attractions that are formed.
Property of matter, I think.