$Na{ H } _{ 2 }{ PO } _{ 4 }+NaOH\rightarrow { Na } _{ 2 }{ HPO } _{ 4 }+{ H } _{ 2 }O\quad \quad -(i)$

1. $Ag _2CrO _4\rightleftharpoons 2Ag^++{CrO _4}^{2-}$
   
   
   $Ksp=(2s)^2\times s=4s^2$
   
   
   $Ksp=(1.1\times 10^{-12})$
   
   
   $S=3\sqrt {\cfrac {Ksp}{4}}=6.5\times 10^{-5}$M
   
   
   2. $AgCl\rightleftharpoons Ag^++Cl^-$
   
   
   $Ksp=S\times S$  ;       $Ksp=1.8\times 10^{-10}$
   
   
   $S=\sqrt {Ksp}=1.34\times 10^{-5}$M
   
   
   3. $AgBr\rightleftharpoons Ag^++Br^-$
   
   
   $Ksp=S\times S$ ;     $Ksp=5\times 10^{-13}$
   
   
   $S=\sqrt {Ksp}=0.71 \times 10^{-6}$M
   
   
   4. $AgI\rightleftharpoons Ag^++I^-$
   
   
   $Ksp=S\times S$  ;    $Ksp=8.3\times 10^{-17}$
   
   
   $S=\sqrt{Ksp}=0.9\times 10^{-8}$M
   
   
   $\therefore$ Solubility of $Ag _2CrO _4$ is highest, so it will precipitate last.

The salt will dissolve and water will taste salty. Salt particles dissolve in water because they occupy the spaces between the water molecules resulting in spreading of salt particles throughout the particles of water showing particle nature of matter.

Chloride salts include sodium chloride (common salt), potassium chloride, calcium chloride, and ammonium chloride. Most chloride salts are readily soluble in water, but mercurous chloride (calomel) and silver chloride are insoluble, and lead chloride is only slightly soluble.

A universal indicator is a pH indicator composed of a solution of several compounds that exhibits smooth colour changes over a pH value range from 1-14 to indicate the acidity or alkalinity of solutions. Two basic hydroxides do not react with each other as these are bases but not alkali.

Reacting sodium chloride and sulphuric acid at elevated temperature leads to production of sodium bisulphate and hydrogen chloride. Little amount of sodium sulphate is also formed which reacts with the sulphuric acid to yield sodium bisulphate or sodium hydrogen sulphate.
$NaCl\left( s \right) +{ H } _{ 2 }{ SO } _{ 4 }\rightarrow { NaHSO } _{ 4 }\left( s \right) +HCl$

Chloro-alkali process is an industrial process for the electrolysis of sodium chloride. It is used to produce chlorine and sodium hydroxide. Aqueous sodium chloride or brine ina membrane cell.

$AgCl\, (s)$ colors changes when exposed in sunlight.

Ammonium sulfate reacts with water to form sulfuric acid which is highly acidic in nature as it completely dissociates to give hydrogen ions.

When magnesium bicarbonate is boiled $MgCO _3, H _2O$ and $CO _2$ are formed. A small amount of $Mg(OH) _2$ is also formed.

$(A)$  $Ba(NO _3) _2$

Magnesium hydrochloride is hygroscopic in nature and it loses its water molecules with the formation of magnesium oxide. When mixed with hydrated magnesium oxide, magnesium chloride forms a hard material called Sorel cement.

Milk of magnesia is basic, water is neutral and lemon juice is acidic in nature.

In neutralization reaction the strong acid with weak base reaction the solution becomes acidic in nature as the salt formed in it alongwith water.

The presence of salts influences most physical properties of sea water (density, compressibility, freezing point, temperature of the density maximum) to some degree but does not determine them. Some properties (viscosity, light absorbtion,refractive index) are not significantly affected by salinity. (Particle and dissolved matter do affect light absorption in sea water and this influence is used in most optical applications.) Two properties which are determined by the amount of salt in the sea are conductivity and osmotic pressure.

If a salt after rubbing with fingers, gives the smell of ammonia, then the salt may be ammonium chloride.
After rubbing, due to warming, ammonium chloride may decompose to give ammonia and hydrogen chloride.
$\displaystyle NH _4Cl \xrightarrow {warm} NH _3 + HCl$

The phenomenon of crumbling to a powder of sodium carbonate crystals on exposure to air is known as efflorescence.

Deliquescent salts have strong affinity for moisture and become liquid by absorbing moisture from air. It is hygroscopic in nature e.g. calcium chloride, zinc chloride,magnesium chloride,sodium hydroxide.

If acid is added to water the solution that forms is very dilute and small amount of heat is released so this reaction does not produce any salt.

Common kind of hydrolysis occurs when a salt of a weak acid or or weak base or both is dissolved in water. Water spontaneously ionizes into hydroxide anions and hydronium cations. The salt also dissociates into its constituent anions and cations.

Sodium acetate is the sodium salt of acetic acid. Acetic acid reacts with sodium carbonate or sodium hydroxide to form a basic solution of sodium acetate which acts as buffer with acetic acid.

Litmus paper can be used as an indicator to know whether a given substance is acidic, basic or neutral in nature.

Efflorescence, spontaneous loss of water by a hydrated salt,  which occurs when the aqueous vapor pressure of the hydrate is greater than the partial pressure of the water vapour in the air. 

In neutralization reaction weak base reacts with strong acid to give salt of strong acidic solution and water.

Sodium carbonate and sodium bicarbonate are basic salts which turn red litmus blue as they are alkaline in nature having pH more than 7.

A salt is a general name given to the chemical produced during the neutralization reaction between an acid and a base.

Approximately for every litre of seawater there is $35$ $g$ of salt.

An efflorescent substance is a chemical which has water associated with its molecules, and which, when exposed to air, loses this water through evaporation. An example of an efflorescent substance is the common copper(II) sulfate crystal $(CuSO _4.5H _2O)$, a blue crystalline solid that when exposed to air, slowly loses water of crystallization from its surface to crystallize to form a white layer of anhydrous copper(II) sulfate.

$(A)$  $ZnCl _{2}$

In this reaction water is being released. This type of substance is known as efflorescent substance.

If there are three moles of $H _2O$ for every one mole of $\displaystyle LiClO _4$. The hydrate formula would be $\displaystyle LiClO _4 \cdot 3H _2O $

In this experiment, a known mass of hydrated copper(II) sulfate is heated to remove the water of crystallization and then weigh into it between 2 g and 3 g of hydrated copper(II) sulphate.A deep blue copper compound is made white through the addition of heat.So the apparatus needed is crucible,cover,tongs and triple beam balance.

Lithium nitrate, $\displaystyle LiNO _3$  dissociates completely when placed into excess amounts of distilled water.
It is a strong electrolyte.
$\displaystyle LiNO _3 \rightarrow Li^+  +  NO _3^-$

$(B)$  Sodium chloride, $NaCl$

Sodium chloride in water is a brine solution which gives sodium hydroxide in aqueous solution and hydrogen and chlorine gases. It is known as chloralkali process. It is an industrial process for the electyrolysis of sodium chloride. It is the technology which is used to produce chlorine and caustic soda(sodium hydroxide) on commercial scale.

Base hydrolysis results in basic solution.

A base hydrolysis reaction will resemble the reaction for base dissociation. A common weak base that dissociates in water is ammonia:

$NH _3 + H _2O \rightarrow NH^{4+} + OH^-$

In the hydrolysis of ammonia, the ammonia molecule accepts a proton from the water (because water acts as a Bronsted-Lowry acid), producing a hydroxide anion ($OH^-$). Similar to a basic dissociation reaction, ammonia forms ammonium and a hydroxide from the addition a water molecule. 

$NH _4Cl $ when dissolved in water undergoes cationic hydrolysis as follows: 
$NH _4Cl $ $\rightarrow $ $NH _4 ^+ + Cl^- $
Ammonium ion being a strong acid takes $OH^- $ ions furnished by water as : 
$NH _4^+ + H _2O \rightarrow NH _4OH\  (freely\  ionized) + H^+ $
Thus concentration of $OH^-$ ions decreases and that of $H^+ $ ion increases due to cationic hydrolysis and consequently the solution become acidic in nature. 

Calcium oxide $(CaO)$ absorbs moisture and hence, can be used for drying gases.

Hydrolysis of salts is reverse of neutralisation reaction.

$Cu[(NH _3) _4]SO _4 \rightarrow Cu[(NH _3) _4]^{2+} + SO _4^{2-}$

A salt of strong acid and weak base undergo hydrolysis on action with water and flourishes $H^{+}$ ion due to hydrolysis of cation. Hence, an aqueous solution of a salt of a weak base and a strong acid is acidic.

$NaKCO _3\rightarrow Na^++K^++CO _{3}^{-2}$
$CaOCl _2\rightarrow Ca^{+2}+OCl^-+Cl^-$
$NH _4HSO _4\rightarrow NH _{4}^{+}+HSO _{4}^{-}$
(2 types of radicals)
$Na(NH _4)HPO _4\rightarrow Na^++NH _{4}^{+}+HPO _{4}^{-}$

Molecular mass of $Na _2SO _410H _2O=2\times23+32+16\times14+1\times20=322$

More the heat absorbed, more will be the cooling effect. Hence more the positive value of $\Delta H$ more the cooling effect.In the given question KBr has $\Delta H =83.3 kJmol^-$ which is highest among all the gases.

Concept :-

Calcium chloride is hygroscopic in nature and its anhydrous salt is deliquescent and it can accumulate enough water in its crystal lattice to form a solution. It is used as a drying agent to absorb moisture from the environment.

Addition of salt on roads is used to melt the ice, as this causes the lowering of the freezing point of the ice. Hence, freezing point of the ice due to the addition of the salt decreases the freezing point lesser than the $0^oC$.
Which can not be obtained easily , hence ice melts.
Now , as per formula
$ \Delta T _f = i k _f m$
Here , $i = $Vant Hoff's Factor.
which depends upon the number of dissociated ions, more the ions are dissociated from a single formula unit, more will be value of the $i$.
and $i \propto \Delta T _f$
hence , this means higher the value of $i$ , more will be lowering of the freezing point.
So here the (B) $MgCl _2$ is used , which has $i = 3$.