Physics help

<p>can someone help me with these 2 problems? Use PV = nRT</p>

<li><p>A tank contains 21.6 kg os nitrogen at an absolute pressure of 3.65 atm. what will the pressure be if the nitrogen is replaced with an equal mass of Co2.</p></li>
<li><p>if 25.50 mol of helium gas is at 10degrees Celsius and a gauge pressure of .35 atm, what is A) teh volume, and the B) temperature if the gas is halved and the volume of gauge pressure is 1 atm.</p></li>
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