The correct options are:
O moles of gas evolved will be lower than they are supposed to be
O the value for your R will be lower than it is supposed to be
If the gas burette is not resting at the bottom of the beaker and the Mg ribbon does not fully dissolve, the following effects on the results can be expected:
O moles of gas evolved will be lower than they are supposed to be: This is likely to occur because some of the gas produced may escape before it is collected in the burette. The incomplete dissolution of Mg ribbon would result in a lower amount of gas being evolved.
O the value for your R will be lower than it is supposed to be: The ideal gas constant (R) is calculated using the ideal gas equation PV = nRT. If the moles of gas evolved are lower than expected, it will affect the calculation of R, leading to a lower value.
O the value for your R will be higher than it is supposed to be: This statement is incorrect. If the moles of gas evolved are lower, it would lead to a lower value for R, not a higher one.
moles of gas evolved will be higher than they are supposed to be: This is not likely to occur. If the gas burette is not properly positioned, some of the gas may escape, leading to a lower measurement of the moles of gas evolved, not higher.
So, the correct options are:
O moles of gas evolved will be lower than they are supposed to be
O the value for your R will be lower than it is supposed to be