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12 March, 13:35

Anyone know how to calculate moles? for chem.

If the atmospheric pressure in the laboratory is 1.2 atm, how many moles of gas were in each syringe?

^ this is my question

Trial 1:

volume for syringe: 4.2 ml

temperature: 0.9 - C

Trial 2:

volume for syringe: 4.1 ml

temperature: 0.9 - C

if you could also explain well I would appreciate it!

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Answers (2)
  1. 12 March, 14:02
    0
    Trial 1 : n = 0.0002241 moles

    Trail 2 : n = 0.0002188 moles

    Explanation:

    Let's bring out the data in the question;

    Pressure (P) = 1.2 atm

    Number of moles (n) = ?

    Both trials contain different values of Volume (V) and temperature (T)

    The equation that relates all four parameters (V, T, P and n) is the ideal gas equation. It is given as;

    PV = nRT where R = gas constant = 0.0821 L atm K-1 mol-1

    Soving for n, we have;

    n = PV / RT

    Trial 1

    Volume (V) = 4.2 ml = 0.0042 L (Converting to L by dividing by 1000)

    Temperature (T) = 0.9 + 273 = 273.9K (Converting to Kelvin temperature)

    n = (1.2 * 0.0042) / (0.0821 * 273.9)

    n = 0.00504 / 22.48719

    n = 0.0002241 moles

    Trial 2

    Volume (V) = 4.1 ml = 0.0041 L (Converting to L by dividing by 1000)

    Temperature (T) = 0.9 + 273 = 273.9K (Converting to Kelvin temperature)

    n = (1.2 * 0.0041) / (0.0821 * 273.9)

    n = 0.00492 / 22.48719

    n = 0.0002188 moles
  2. 12 March, 14:02
    0
    Since according to ideal gas law, PV=nRT and you have 1.2atm, plug in the value for volume but make sure to convert to L instead of mL and convert temperature to Kelvin
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