What type of solution is obtained from an amalgam of mercury with sodium?

$3.0\, g$ of oxalic acid $[(CO_2H)_2 \cdot 2H_2O]$ is dissolved in a solvent to prepare a $250\, mL$ solution. The density of the solution is $1.9\, g/mL$. The molality and normality of the solution,respectively,are closest to

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: At $10^{\circ} C$,the density of a $5 \ M$ solution of $KCl$ is given. The solution is cooled to $-21^{\circ} C$. The molality of the solution will remain unchanged.
Reason $R$: The molality of a solution does not change with temperature as mass remains unaffected by temperature.
In the light of the above statements,choose the correct answer from the options given below:

When $1.04 \ g$ of $BaCl_2$ is dissolved in $10^5 \ g$ of water,what will be the concentration of the solution in $ppm$?

$A$ certain aqueous solution of $FeCl_3$ (formula mass $= 162 \ g/mol$) has a density of $1.1 \ g/mL$ and contains $20.0 \ \% \ FeCl_3$ by mass. The molar concentration (molarity) of this solution is: (in $M$)

If $4 \ g$ of $NaOH$ dissolves in $36 \ g$ of $H_2O$,calculate the mole fraction of each component in the solution. Also,determine the molarity of the solution (specific gravity of the solution is $1 \ g \ mL^{-1}$).