Error is a daily challenge within the chemistry world. Not every reaction in the lab yields 100% of what you put in, but trying to achieve the closest possible yield to 100% is the goal of every chemist. What limits this goal is a general concept of error. Sources of error range from measurement limits, loss between transferring samples, and mistakes.
Technology is only so precise when it comes to measuring properties. The more accurate the measurement, the more expensive the equipment becomes. Depending on what the experiment is, certain amounts of error due to measurement readings are acceptable.
When measuring chemicals and conducting reactions, some of the material may stay behind in the flask or tool used to measure. While it is good practice to remove as much product as possible so the yield is high, scraping every bit of content from the container is unnecessary. It is acceptable that some of the product may be lost during transferring. However, it is best to avoid transferring too many times as the loss of product adds up.
In regards to mistakes, include spilling some of the sample, washing a product with too much solvent, and general improper techniques when conducting an experiment. These are sources of error that can easily be avoided to improve the yield of the experiment significantly if proper care and knowledge is applied.
When determining the error within an experiment, the following equation is used: Obtained value minus Theoretical value all divided by Theoretical value. This number is multiplied by 100 and the percent error is obtained. Depending on the experiment conducted will determine if the error is reasonable.