An acid Multiple Choice donates electrons in an electron transfer reaction. None of these choices are correct. produces hydroxide ions when dissolved in water. donates protons in a proton transfer reaction. changes the color of phenolphthalein indicator from colorless to pink.

Answer: donates protons in a proton transfer reaction.

Explanation:

According to the Arrhenius concept, an acid is a substance that ionizes in the water to give hydrogen ion and a base is a substance that ionizes in the water to give hydroxide ion.

According to the Lewis concept, an acid is defined as a substance that accepts electron pairs and base is defined as a substance which donates electron pairs.

Phenolphthalein is an indicator which produces pink colour on adding into a base and turns colourless on adding to an acid.

Thus the only correct option is an acid donates protons in a proton transfer reaction.