Which soil pH value is considered to be acidic soil?

$(a)$ Give the chemical names of acids present in:
$(i)$ ants
$(ii)$ lemon
$(iii)$ milk
$(iv)$ tomato

You have two solutions $A$ and $B$. The $pH$ of solution $A$ is $6$ and the $pH$ of solution $B$ is $8$. Which solution has more hydrogen ion concentration? Which one of these is acidic and which one is basic?

In the following schematic diagram for the preparation of hydrogen gas as shown in the Figure,what would happen if the following changes are made?
$(a)$ In place of zinc granules,the same amount of zinc dust is taken in the test tube.
$(b)$ Instead of dilute sulphuric acid,dilute hydrochloric acid is taken.
$(c)$ In place of zinc,copper turnings are taken.
$(d)$ Sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated.

$Na_{2}CO_{3} \cdot 10H_{2}O$ and $Na_{2}CO_{3}$ are two chemical compounds. Write their chemical names. Explain the significance of $10H_{2}O$ and mention the term used for water molecules attached to a salt.

$A$ 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?