The unknown liquid is methanol and its density is 791 kg/m^3 at 25 degree C. What is your percent error in the experiment?
When we carry out experiments, we obtain some parametric values and these measured values are compared against the standard or accepted values. The percentage error in the parametric values is determined by comparing the measured and accepted values as:
% error = ([measured value - accepted value] / accepted value) x 100
Thus, we need both the measured value and the accepted value for determining the percentage error. In the given question, only the accepted value (791 kg/m^3) is given and the measured value is missing. In absence of complete data, we cannot determine the % error.
For example, if you measured a value of say, 790 kg/m^3 as the density, then the % error in your experimental value is:
% error = ((790 - 791)/791) x 100 = 0.126%
That means you measured a slightly different (in this case smaller) value of density as compared to the accepted value.
Hope this helps.