1. Some reactions will present an actual yield lower than the theoretical yield, and this can occur due to many situations, a couple of the reasons why that we can list is that some reactions don't have the reactants actually reacting to form the products, and another reason why is the loss of reactants in the process for many possible situations.
4. According to the solubility curve, if we have 30 grams of NH4Cl at 50°C, the reaction will be unsaturated