Hai,

First of all  the question hasn't mentioned whether it is in standard temperature and pressure.

So we just assume the temperature and pressure remains constant .

Therefore we use the equation of

PV=nRT........ (1)

(the ideal gas equation)

From it we get the equation of

V1/V2=n1/n2.... ...... (2)

On substituting the values

2.5/V2=0.5/0.55

V2=2.75

I hope the answer is clear to you..

Greeting,

Very simple volume and no. of moles are directly proportional i.e. applying Avagadro's law i.e. V1/n1=V2/n2

Where V1=0.5 L, V2=?,  n1=0.5 moles, n2=0.55 moles

There by applying avagadro's law:

0.5 L/0.5 moles=V2/0.55 moles

V2=0.55 L is the answer