Question

You have a 5-liter container with 2.00 x 1023 molecules of ammonia gas (NH3) at STP. How many molecules of argon gas (Ar) are in an identical container at the same temperature and pressure?

A. 6.02 x 1024 molecules
B. 1.30 x 1024 molecules
C. 2.00 x 1023 molecules
D. 6.02 1023 molecules

Answer 1

C. 2.00 x 1023 molecules

Step-by-step explanation:

Given , the pressure , volume and temperature are same in both cases.

From the ideal gas equation,

P V = n R T

where n= no. of moles = given weight ÷ atomic weight

And 6.023 x 10^23 molecules of ammonia(NH3), weigh 17g ( 14 + 3(1 ))

So we have

P V = ((2.00 x 10^23)/(6.023 x 10^23)) x R T

Similarly, say n molecules of argon gas (Ar) are in an identical container.

So the gas equation would be

P V = ( n / 6.023 x 10^23 ) x R T

Because, atomic weight of Argon is beared by 6.023 x 10^23 molecules.

dividing these two equations, we get

n = 2.00 x 10^23 molecules