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Question

A 250 mL sample of gas was initially at a pressure of 101 kPa at 80°C. If the volume decreases to 100 mL at 50°C, how would you calculate the new pressure?

I would calculate it by doing this:

101 kPa x 100mL/250mL x 373K/323K

Answer 1

Hello

Use the combined gas law equation:

P₁ V₁             P₂ V₂
---------    =     ---------
   T₁                  T₂

P₁ = 101 kPa                          P₂ = ?
V₁ = 250 mL                            V₂ = 100 mL
T₁ = 80°C + 273 = 353 K      T₂ = 50 °C + 273 = 323 K

Rearrange to solve for P₂

              P₁ V₁ T₂
P₂   =  ----------------
                V₂ T₁

            101 kPa x 250 mL x 323 K
       =  -----------------------------------
              100 mL x 353 K

       = 231 kPa