The formula weight of $H_2SO_4$ is $98$. The weight of the acid in $400 \ mL$ of $0.1 \ M$ solution is ........... $g$.

Which of the following statements is correct?
$(1)$ Molarity is the number of moles of solute in one liter of solution.
$(2)$ The normality and molarity of a sodium carbonate solution are the same.
$(3)$ The number of moles of solute dissolved in $1000 \ g$ of solvent is defined as molality $(m)$.
$(4)$ The ratio of the mole fractions of solute and solvent is equal to the ratio of their respective moles.

Which of the following statements is true?
$(1)$ $200 \ mL$ of $0.2 \ M \ NaOH$ has the same number of moles of solute as $1000 \ mL$ of $1 \ M \ NaOH$.
$(2)$ $200 \ mL$ of $1 \ M \ NaOH$ has the same number of moles as $1000 \ mL$ of $0.2 \ M \ NaOH$.
$(3)$ $100 \ mL$ of $0.2 \ M \ NaOH$ has the same number of moles as $1000 \ mL$ of $1 \ M \ NaOH$.
$(4)$ $2000 \ mL$ of $0.2 \ M \ NaOH$ has the same number of moles as $1000 \ mL$ of $1 \ M \ NaOH$.

How much water should be added to $200 \, cc$ of a semi-normal solution of $NaOH$ to make it exactly deci-normal?

Molarity of $4\%$ $NaOH$ solution is ......... $M$.

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?