What is the number of moles in 40.0 L of He gas at STP?

There are 1.78 moles in 40.0 L of He gas at STP

Explanation:

According to ideal gas equation:

P = pressure of gas = 1 atm (STP)

V = Volume of gas = 40.0  L

n = number of moles = ?

R = gas constant =

T =temperature =   (STP)

Thus there are 1.78 moles in 40.0 L of He gas at STP

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.