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.
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).
When calcium oxide (CaO) reacts with nitric acid (HNO3), calcium nitrate (Ca(NO3)2) and water (H2O) are formed. The addition of a universal indicator allows us to observe the color changes that occur during the reaction.
The universal indicator is a mixture of several different indicators that undergo color changes at different pH levels. The pH scale ranges from 0 to 14, with values below 7 considered acidic, 7 being neutral, and values above 7 being alkaline/basic.
At the start of the reaction, when the calcium oxide and nitric acid are mixed, the nitric acid (HNO3) donates its H+ ions to the calcium oxide (CaO). This results in the formation of water (H2O) and calcium nitrate (Ca(NO3)2):
CaO + 2HNO3 → Ca(NO3)2 + H2O
Initially, due to the presence of the strong acid, the solution will be highly acidic. The universal indicator added will likely show a distinct color within the acidic pH range, such as red or orange, indicating a low pH below 7.
As the reaction progresses, the calcium oxide neutralizes the acid, resulting in a decrease in the concentration of hydrogen ions (H+). This leads to a rise in pH towards neutral. The universal indicator will gradually transition through the pH scale, changing color from red or orange to yellow, green, and finally blue or purple as the solution becomes more alkaline/basic.
Ultimately, when calcium nitrate and water are formed, the solution will tend to be slightly alkaline/basic. The universal indicator might indicate a bluish or purple color, indicating a pH level slightly above 7.
It is important to note that the exact color changes observed will depend on the specific composition of the universal indicator used and the concentrations of reactants.