The results of this experiment are affected by the care with which each step is

Question

The results of this experiment are affected by the care with which each step is completed. Describe how each of the following errors would affect the calculated value of R. a. The Mg slid into the HCl in the test tube before the system was sealed off. b. The room temperature increased by 5 Degree C between the time that the final volume was measured and the temperature was recorded. c. The MgO coating was not removed before the Mg sample was placed in the HCl. d. The test tube was filled with 4 mL of 0.10 M HCl instead of 4 mL of 1M HCl.

Explanation / Answer

If you are determining "R" the gas consant

then note that

PV = nRT

so

R = PV/(nT)

then

a) if more Mg goes into solution, then more H2(g) is produced, so more P therefore, R increases incorrectly

b) if T increased, then according to the formula, R must decrase... but this is calculated backwards, i.e. we maintain a lower T rather than the higher, so

R is lareger than it should be

c)

MgO + HCl will not produce gas, rather water, so HCl is consumed, but no gas is produced

The ratio is incoreclty calculated so mol of gas are lower than reality, so R is higher than is should be

D)

The limiting reactant is likely to be HCL, incorrect soichoiemtry will relate to lower amount of gas pressure

therefore, lower amount of substance

which implies higher R (incorectly)

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