Acid changes the colour of blue litmus to ________.

The correct answer is Red.

Key Points

•  Acid
  • ​Acid changes the colour of blue litmus to Red.
  • A Brnsted-Lowry acid or Lewis acid is a molecule or ion that can either donate a proton (the hydrogen ion, H+) or establish a covalent bond with an electron pair. Proton donors, also known as Brnsted-Lowry acids, are the first class of acids.
  • Proton donors, also referred to as Arrhenius acids, generate the hydronium ion H3O+ under the unique situation of aqueous solutions.
  • The Arrhenius theory was expanded upon by Brnsted and Lowry to take non-aqueous solvents into account.
  • A hydrogen atom is typically bound to a chemical structure in a Brnsted or Arrhenius acid that is still energetically advantageous after the loss of H+.

Additional Information

• Aqueous Arrhenius acids have distinguishing characteristics that serve as a useful definition of an acid. Acids can turn blue litmus red, produce aqueous solutions with a sour taste, and react with bases and some metals (like calcium) to generate salts.
• The Latin word acidus, which means "sour," is where the word acid comes from. While the technical definition solely refers to the solute, an aqueous solution of an acid with a pH lower than 7 is sometimes commonly referred to as "acid" (as in "dissolved in acid"..
• Higher acidity and, thus, a higher concentration of positive hydrogen ions in the solution are indicative of a lower pH.