A cylinder has a piston at one end that can be moved in or out to change the volume of gas inside. The other end is fitted with a valve. Initially the cylinder contains 2.95 mol of an ideal gas. The piston is now pushed in to decrease the volume of gas to one-third its initial value without causing any change in temperature. In order to keep the pressure constant as well, how many moles of gas need to be released through the valve

0.974 moles

Explanation:

Avogadro's law states that the volume of a given mass of gas is directly proportional to the number of moles present as long as the temperature and pressure are held constant.

Now from the question;

V1 = V

n1 = 2.95

V2 = 1/3 V or 0.33 V

n2 = ?

V1/n1 = V2/n2

V1n2 = V2n1

n2 = V2n1/V1

n2 = 0.33 V * 2.95/V

n2 = 0.974 moles

the answer

explanation:

the capillary tube was too close to the bottom of the beaker.

the ruler may have moved.

water got into the capillary tube.

the temperature was not allowed to equilibrate in the 2-4 minutes.

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm