If you notice that the magnesium metal used appeared to be oxidized, the metal surface was black and full rather than silver and shiny. Would the actual yield (and thus the percent yield) be erroneously high, low, or unaffected by the oxidized metal? Explain
The actual yield (and thus the percent yield) would be erroneously low due to the oxidation of the magnesium metal.
Oxidation refers to the loss of electrons by a substance during a chemical reaction. In the case of magnesium metal, it readily reacts with oxygen in the air to form magnesium oxide (MgO). This chemical reaction results in the metal surface being covered with a layer of black magnesium oxide, which gives it a non-shiny appearance.
When conducting a reaction to obtain a specific product, the starting material (in this case, magnesium metal) is weighed before the reaction begins. The weight of the oxidized magnesium metal would include the weight of the magnesium and the weight of the oxygen that has reacted with it. However, the oxygen is not part of the desired product, and thus its weight should not be included in the calculation of the actual yield of the desired product.
As a result, including the weight of the oxidized metal in the actual yield calculation would erroneously decrease the yield. This would subsequently lead to a lower percent yield, as the actual yield is divided by the theoretical yield (the maximum possible yield). The percent yield, therefore, would be lower than it should be if the oxidized metal was not considered.
In summary, the oxidized metal would result in an erroneously low actual yield and percent yield since the weight of the oxidizing agent (in this case, oxygen) would be accounted for in the actual yield calculation, although it is not part of the desired product.