Final answer:
A reported percent yield of 105% for sand in a Chemistry lab can not be due to more sand than what was originally available; it likely indicates impurities or moisture content. The law of conservation of mass dictates that actual product mass cannot exceed the theoretical mass.
Step-by-step explanation:
In Chemistry, the percent yield of a reaction compares the actual yield to the theoretical yield, expressed in percentage. It is theoretically expected to range from 0% to 100%. However, a percent yield greater than 100% suggests that the product is impure or contains solvent like water, which increases its mass. The law of conservation of mass ensures you cannot get more pure product than what is theoretically possible. If a lab group reports a percent yield of 105% for sand, it cannot mean that there was more sand than initially present; instead, it may indicate that the sand is wet or contains other impurities.
An example of this could be the collection of a reaction product that has absorbed water from the air, which would make the mass of the product larger than the actual amount of desired compound formed. Another possible impurity could be remnants of reaction side products or unreacted starting materials that have not been separated from the desired product. In industrial and laboratory settings, achieving yields as close to 100% is ideal, due to efficiencies and waste disposal concerns.