Final answer:
An increase in potassium level is a likely change in the chemistry of blood if a sample is not processed promptly, due to the potential breakdown of red blood cells that can leak potassium into the serum.
Step-by-step explanation:
If a blood sample is left sitting too long before centrifugation to separate the serum from the cells, the chemistry of the blood can change. Specifically, a likely change that can occur is an increase in the potassium level (B). This happens because erythrocytes (red blood cells) contain large amounts of potassium, which can leak out into the serum if the cells begin to break down or hemolyze. This is in contrast to an increase in carbon dioxide or sodium levels, or changes in pH, which might have different implications or be related to other effects such as respiration or kidney function.
Over the course of an hour in a glass tube, while waiting to be processed, the blood may undergo metabolic changes, such as the consumption of glucose by cells, or a potential breakdown of cells leading to leakage of intracellular ions like potassium into the serum. Blood collection tubes that contain oxalate ions prevent clotting by removing calcium; however, if the intent is to measure serum calcium, it will not be significantly affected by delay in separation.