What is the percent error if students were expected to produce about 80.0g of MgO and the amount they measured after the reaction was 74.6g of MgO?

Error in experimental results is the difference between the theoretical or known value and the experimentally obtained valued. This difference is also called absolute error. Percent error is the ratio of absolute error to the theoretical or expected value. It gives more meaning to the observed error. For example, if you measure a length with an error of 15 cm, it makes a difference if the length measured was 150 cm or 1500 cm. In...

Error in experimental results is the difference between the theoretical or known value and the experimentally obtained valued. This difference is also called absolute error. Percent error is the ratio of absolute error to the theoretical or expected value. It gives more meaning to the observed error. For example, if you measure a length with an error of 15 cm, it makes a difference if the length measured was 150 cm or 1500 cm. In the first case the percent error is 10% and in the second case it's 1%. Percent error puts the amount of error into perspective.

Here's the equation for percent error:

% error = [(theoretical value - experimental value)/theoretical value] x 100%

Using your data:

% error = (80.0g-74.6g)/80.0g x 100% = 6.75%