A student performed an experiment similar to this one in which he reacted 0.0375
ID: 910422 • Letter: A
Question
A student performed an experiment similar to this one in which he reacted 0.0375 g of magnesium in a gas buret filled with water and excess hydrochloric acid. The temperature in the room was 21.0 °C, the lab barometer read 29.85 in Hg, and 38.93 mLof gas?
were collected in the buret.
For this experiment, the number of moles of hydrogen gas generated was ????
moles, the temperature was ????? K, the volume of hydrogen gas collected was ????
L, and the pressure of hydrogen gas collected was ???? atm.
Using this data, the student's calculated value of R was ????
L•atm/mol•K.
His percent deviation from the literature value of R was ?????
% (round your answer to 2 significant figures).
Explanation / Answer
The required reaction is
Mg + HCl --------> MgCl2 + H2
gas collected in the buret is Hygrogen.
1 mole of hydrogen is produced from 1 mole of magnesium. Moles of hydrogen produced = 0.0375/ 24 = 1.56 *10-3 mole
PV = nRT
n = PV/ RT
Volume of gas collected = 38.93 ml = 0.03893 L
pressure of the gas = 29.85 mm Hg = 0.039 atm
temp = 294 K
R = PV/nT = 0.039 * 0.03893 / 1.56 *10-3 * 294 = 0.0033 L atm/K/mole
%deviation = 0.0033*100/0.082 = 4.02 % = 4.0 % (two significant fig)
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