Flask X contains 5dm3 of He at 12kPa and flask Y contains 10dm3 of Ne at 6kPa.If the flasks are connected ...

If the flask are connnected at constant temperature, what is the final pressure??

Hello

you use the equation
p1*V1 = p2*V2 --> p2 = p1*V1/V2

The final volume will be 15 L.
So the (partial) pressure of the Helium decreases to 12*5/15 = 4 kPa,
and the (partial) pressure of the Neon to 6*10/15 = 4 kPa

The total new pressure will be the sum of the two partial pressures = 8 kPa

Regards