Solid sodium bicarbonate was placed on a strip of pH paper. The colour of the strip:

The correct answer is Did not change.

Key Points

• Sodium bicarbonate (NaHCO3) is a weak base and slightly alkaline in nature.
• pH paper is an indicator that changes color based on the pH of the substance it comes into contact with.
• Solid sodium bicarbonate typically has a pH around 8-9 when dissolved in water, but the solid form does not readily change the pH paper color.
• The color of the pH paper does not change significantly because the bicarbonate ions in the solid form are not free to react with the paper.

Additional Information

• pH Scale
  • The pH scale ranges from 0 to 14, where 7 is neutral, below 7 is acidic, and above 7 is basic (alkaline).
  • The pH paper is a tool used to measure the acidity or alkalinity of a solution.
• Sodium Bicarbonate
  • Commonly known as baking soda, sodium bicarbonate is used in cooking, cleaning, and sometimes as a medicinal antacid.
  • It is a chemical compound with the formula NaHCO3.
• Indicators
  • Indicators are substances that change color in response to changes in pH.
  • Common indicators include litmus paper, phenolphthalein, and methyl orange.
• Reactivity of Solids
  • Solid compounds are generally less reactive with indicators compared to their aqueous solutions.
  • This is because the ions in solids are not free to interact with the indicator.