$500 \ ml$ aqueous solution is prepared by dissolving $2$ moles of $HCl$ in water. What will be the molarity of this solution (in $M$)?

The marble statues are often slowly corroded when kept in the open for a long time. Give a suitable reason.

$R$. $K$. Patel,a chemistry teacher,explained the properties of inorganic acids in Std. $10$. He intentionally stated one of the properties incorrectly. Identify which one was wrong.

Which of the following substances is an antacid?

Explain the action of dilute hydrochloric acid on the following with chemical equations:
$(a)$ Magnesium ribbon
$(b)$ Sodium hydroxide
$(c)$ Crushed egg shells

$A$ sample of soil is mixed with water and allowed to settle. The clear supernatant solution turns the pH paper yellowish-orange. Which of the following would change the colour of this pH paper to greenish-blue?