To determine the condensation reaction that occurs when urea is heated in a test tube, we need to understand the composition and behavior of urea. Urea is an organic compound with the chemical formula (NH₂)₂CO. When heated, urea decomposes into two molecules of ammonia (NH₃) and carbon dioxide (CO₂) through a reaction called thermal decomposition.
The formula for the thermal decomposition of urea can be represented as:
(NH₂)₂CO → 2NH₃ + CO₂
Moving on to the second part of the question, when copper sulfate (CuSO₄) and sodium hydroxide (NaOH) are added to the test tube, a reaction occurs known as a precipitation reaction. This reaction results in the formation of a solid, which is typically a precipitate.
The chemical equation for the reaction between copper sulfate and sodium hydroxide is:
CuSO₄ + 2NaOH → Cu(OH)₂ + Na₂SO₄
The resulting precipitate is copper(II) hydroxide (Cu(OH)₂), which appears as a blue solid.
Comparing this reaction to the tube where copper sulfate, sodium hydroxide, and a solution of egg white are mixed, we can observe a different color change. Egg white contains proteins, and one of the characteristics of proteins is their ability to bind with copper ions (Cu²⁺) in basic solutions.
Copper ions form coordination complexes with the protein molecules, resulting in a color change. In basic solutions, copper ions react with the protein structure and give a characteristic blue or purple color.
Therefore, the color observed when copper sulfate, sodium hydroxide, and a solution of egg white are mixed is typically a blue or purple color due to the interaction between the protein molecules and copper ions in a basic solution.