calcium oxide and nitric acid react to form calcium nitrate and water. at the start of the reaction, some universal indicator is added. suggest how the colour changes throughout the reaction. explain.

Answer 1

At the start of the reaction, calcium oxide (CaO) and nitric acid (HNO3) are both colourless. However, once the reaction begins, the solution will slowly turn yellow as nitric acid is an acidic compound. The universal indicator will likely show a yellow coloration indicating an acidic solution.

As the reaction progresses, calcium nitrate (Ca(NO3)2) and water (H2O) will be formed. Calcium nitrate is a soluble salt, and as it dissolves in water it will create an aquous solution. Calcium nitrate is colorless and will not affect the color of the solution.

Since calcium oxide is a strong base, it reacts with nitric acid creating a neutral solution, which is green on the universal indicator. So, towards the end of the reaction, when the calcium oxide completely reacts with nitric acid, the solution will turn green, indicating a neutral pH.

Therefore, the color changes of the universal indicator during the reaction will start with a yellowish tint (a slightly acidic solution) and will eventually turn green (a neutral solution).