When you combine starch, iodine, amylase, and hydrochloric acid (HCl) with a pH of 2, the final color of the mixture would depend on the reaction between these components.
Normally, starch reacts with iodine to form a blue-black complex. However, when amylase, which is an enzyme that catalyzes the breakdown of starch, is present, it can break down starch into simpler molecules such as maltose.
In the presence of hydrochloric acid (HCl) with a pH of 2, the activity of amylase may be affected. The optimal pH for amylase activity is typically closer to neutral or slightly alkaline. Acidic conditions may denature or inhibit the enzyme, reducing its ability to break down starch effectively.
If the amylase activity is significantly affected by the acidic conditions, the breakdown of starch may be slowed down or inhibited. In this case, the iodine would not encounter the broken-down starch molecules and would continue to form the blue-black complex with the starch, resulting in a blue-black color.
On the other hand, if the amylase activity is not completely inhibited by the acidic conditions, the amylase may still partially break down the starch molecules. This would result in a mixture of broken-down starch products and starch itself. In this case, the iodine would react with the remaining starch to form the blue-black complex, but the color might be lighter or less intense compared to a reaction without the presence of HCl.
It's important to note that the exact outcome and color would depend on the concentrations of each component, the reaction conditions, and the specific behavior of the amylase enzyme in acidic conditions. The final color could range from a dark blue-black to a lighter blue-black, or even a less intense color if the starch breakdown is significant.