Which of the following formulae is correct for calculating the number of moles?

Acid and base react with each other and form salt and water. What is this reaction called in scientific language?

Equal lengths of magnesium ribbon are taken in two test tubes $A$ and $B$. $H_{2}SO_{4}$ is added to test tube $A$ and $H_{2}CO_{3}$ in test tube $B$ in equal amounts.
$(a)$ Identify the test tube showing vigorous reaction.
$(b)$ Give reason to support your answer.
$(c)$ Name the gas liberated in both the test tubes. How will you prove its liberation?

Which of the following substances enters our body when a red ant bites us?

During the preparation of hydrogen chloride gas on a humid day,the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to

Which of the following phenomena occur when a small amount of acid is added to water?