What is the correct observation when barium metal is added to an excess of water? A Forms a colourless solution only B Forms a colourless solution and effervesces C Forms a white precipitate only D Forms a white precipitate and effervesces - AQA - A-Level Chemistry - Question 15 - 2019 - Paper 3

When barium metal is added to water, it reacts to produce barium hydroxide and hydrogen gas. The reaction is exothermic, producing heat, which causes the hydrogen gas to effervesce. The barium hydroxide formed is soluble in water, resulting in a colourless solution. Thus, the correct observation is that barium forms a colourless solution and effervesces.