<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
Answer:
1.332 meters per second. // 2.664 meters per second.
Explanation:
the slower person moved 33.3 meters, and the faster person moved 66.6 meters.
the slower person is moving 33.3 meters in 25 seconds, while the other person is moving 66.6 meters in 25 seconds
slower person moved 33.3/25 = 1.332 meters per second.
faster person moved 66.6/25 = 2.664 meters per second.