What is the molar concentration of chloride ion in a solution made by adding $300 \ mL$ of $3.0 \ M$ $KCl$ solution to $200 \ mL$ of $4.0 \ M$ $BaCl_2$ solution? $........ \ M$

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:

The molality of $1 \ M$ solution of $NaCl$ (specific gravity $1.0585 \ g/mL$) is

Calculate the molarity of $NaOH$ solution prepared by dissolving $0.4 \ g$ of $NaOH$ in enough water to form $500 \ mL$ of the solution. (in $M$)

What is the mass of the solute in $g$ in $1 \ L$ of a solution having $40\%$ concentration by weight? The density of the solution is $1.2 \ g/mL$.

If $0.0100 \ g$ of urea $[(NH_2)_2CO]$ is added to $0.3000 \ m^3$ of water,what is the molality of the urea solution?