I am doing the Evaluation of the Gas Law Constant. Please helpa answer these que
ID: 828067 • Letter: I
Question
I am doing the Evaluation of the Gas Law Constant. Please helpa answer these questions
What do you feel is the largest source of experimental error in your determination of R? What would be the effect (increase, decrease, or no change) on the calculated value of R of each of the following experimental errors? Explain each answer. The liquid level in the eudiometer tube is lower than that in the beaker, but this is not taken into consideration in the calculations. The balance used to weigh the magnesium gives a mass that is higher than actual, Some H2 escapes into the beaker during the reaction. Most top-loading balances used in this experiment measure a mass only to the nearest mg (plusminus 0.001 s). This significantly affects the calculation of R in this experiment. Explain why this is so. How might the procedure be modified to compensate for this systematic error?Explanation / Answer
1
a) The gases are not perfectly "perfect" or "ideal", because concept of an ideal gas is an "ideal concept" itself!
b) Experimental errors (not collecting the gas properly, not mixing proper amount of chemicals, leak in the collection bulb, etc)
c)Hydrogen gas might be mixed with impurities like water vapor.
d)imprecision of instument may result in error
2
a) An air bubble was trapped in the eudiometer once it is being inverted in the beaker.
This would mean that you would start with an existing volume of gas present in the system (V(initial) ? 0), so your final volume would be greater than the theoretical value. Because R is directly proportional to V, the calculated value of R would be greater than the true value.
b) Some Mg adheres to the inside wall of the audiometer tube after the reaction has ceases and the acid level is quite a bit lower than the piece of Mg
This would mean that you did not react all of the magnesium, so the volume of gas produced would be less than the theoretical value. Because R is directly proportional to V, the calculated value of R would be less than the true value.
c) Some H2 escapes into the beaker during the reaction.
so R will decrease
because
PV=NRT
3
because it involves recation
Mg+2HCl=MgCl2 +H2
so even a small change in amount of mg will have a larger impact on change in volume of hydrogen gas because hydrogen gas will occupy very large space
thus R will get affected.
because
PV=NRT
sowe should take utmost care so that no change in mg occur.
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