What is observed when excess sulfur dioxide is bubbled into a solution of sodium hydroxide containing red litmus paper
When excess sulfur dioxide is bubbled into a solution of sodium hydroxide containing red litmus paper, the litmus paper will turn blue.
Now, let's understand the chemistry behind this observation:
1. Sulfur dioxide (SO2) is a colorless gas with a pungent smell. It is a common byproduct of burning fossil fuels.
2. Sodium hydroxide (NaOH) is a strong base commonly known as caustic soda. It is a white, solid substance.
3. Red litmus paper is a pH indicator that turns red in an acidic solution and blue in a basic solution.
When sulfur dioxide is bubbled into sodium hydroxide solution, the following reaction occurs:
SO2(g) + 2NaOH(aq) → Na2SO3(aq) + H2O(l)
The sulfur dioxide reacts with sodium hydroxide to produce sodium sulfite (Na2SO3) and water (H2O). Sodium sulfite is a basic compound.
As a result of this reaction, the solution becomes basic due to the formation of sodium sulfite, which is a salt of a strong base (NaOH) and a weak acid (SO2). This change in pH causes the red litmus paper to turn blue, indicating that the solution has become basic.
In summary, when excess sulfur dioxide is bubbled into a solution of sodium hydroxide containing red litmus paper, the red litmus paper turns blue due to the formation of a basic solution resulting from the reaction between sulfur dioxide and sodium hydroxide.