Answer: Option C. -> Antacid
:
C
Indigestion causes acidity in the stomach. We take antacids, which are basic in nature,to neutralise the acidity. However, theycannot treat more serious problems like appendicitis,stomach ulcer, etc. Example of antacids arealuminium hydroxide, magnesium carbonate, etc.

Answer: Option A. -> True
:
A
When acids react with carbonates water, carbon dioxide and salt are produced. In general:
acid + metal carbonate $\to$ salt + water + carbon dioxide

Answer: Option D. -> CH3COONa
:
D
Basic salts are formed from the neutralisation reaction between astrong base and a weak acid.
Here, sodium acetate (${\text{CH}}_3\text{COONa}$)is a basic salt because it is formed from the reaction between sodium hydroxide which is a strong base($\text{NaOH}$) and acetic acid (${\text{CH}}_3\text{COOH}$) which is aweak acid. The reaction involved is given below:
$\text{NaOH(aq)}+{\text{CH}}_3\text{COOH(aq)}\to {\text{CH}}_3\text{COONa(aq)}+{\text{H}}_2\text{O(aq)}$
Hydrochloric acid ($\text{HCl}$) is an acid, sodium chloride($\text{NaCl}$) is a neutral salt and tin chloride(${\text{SnCl}}_2$) is an acidic salt.

Answer: Option B. -> Reaction between a metal oxide and water
:
B
- Metaloxides react with water to formbases by associating with hydroxyl ion present in water. For example, the chemical reaction between calcium oxide and water:
$\text{CaO}\text{(s)}+{\text{H}}_2\text{O}\text{(l)}\to {\text{Ca(OH)}}_2\text{(aq)}$
- Basic oxides can be made by the direct combination of metals with oxygen.
-Heating of metal carbonates produces metal oxide and releases ${\text{CO}}_2$ gas.
- Salt and water are formed when acid reacts with base.

Answer: Option D. -> Na2CO3⋅10H2O
:
D
${\text{Na}}_2{\text{CO}}_3\cdot 10{\text{H}}_2\text{O}$ is the chemical formula of washing soda. It is a water soluble sodium salt of carbonic acid. It is mainly used for washing clothes.

Answer: Option B. -> NH4Cl
:
B
A salt formed from either weak acid or a weak base will get hydrolysed. Salts like $NaCl$,$KCl$ and$CaC{l}_2$ are formed from strong acid($HCl)$ & strong bases like $NaOH$ and $KOH$ respectively. Such salts formed from the reaction of strong bases and strong acids doesn't get hydrolysed.
${NH}_{4}Cl$ is formed from a weak base and a strong acid and therefore is an acidic salt.
${NH}_{4}Cl$ is hydrolysed in water to give [$H^{+}$].
${NH}_{4}Cl$ + $H_{2}O$ ⇔${NH}_{4}OH$ + $HCl$
$HCl\to H^{+}+C{l}^{-}$
Here, $HCl$ is the strong acid formed and $N{H}_{4}OH$ is the weak base obtained.

Answer: Option B. -> False
:
B
The given statement is false. Most of the metals react with acids. The metals which are more reactive than hydrogen can replace the hydrogen ion from an acid. For example, sodium, potassium can replace hydrogen from acids. The equation for the reaction of sodium and potassium with dilute hydrochloric acid is given below.
$2Na\left(s\right)+2HCl\left(aq\right)\to 2NaCl\left(aq\right)+H_2\left(g\right)$
$2K\left(s\right)+2HCl\left(aq\right)\to 2KCl\left(aq\right)+H_2\left(g\right)$
The metals which are less reactive than hydrogen cannot replace it from acids. For eg. Gold, Platinum etc.
So the given statement is false.

Answer: Option B. -> donate protons
:
B
Acids are defined by their ability to donate protons. Mineral acids like ${\text{H}}_2{\text{SO}}_4$ donate protons easily, so, they are strong acids. Organic acids like ${\text{CH}}_3\text{COOH}$ do notdonate their protons so easily, hence they are weak acids.

Answer: Option D. -> Double salt
:
D
Potash alum is potassium double sulphate of aluminium, i.e. a double salt as it contains more than one cation. Its formula is $KAlS{O}_4$. So, the cations present in potash alum are $K^{+}$ and $A{l}^{+3}$.

Answer: Option C. -> The negative logarithm of hydrogen ion concentration.
:
C
pH is the negative logarithm of hydrogen ion concentration in a solution. It tells us about the strength of acids and bases.
On a pH scale which ranges from 0 to 14, acidic solutions will have a pH value less than 7 and alkaline(or basic) solutions have their pH value more than 7.