Sagot :
SOLUTION:
Step 1: Calculate the number of moles of solute (NaOH).
The molar mass of NaOH (caustic soda) is 40 g/mol.
[tex]\begin{aligned} n_{\text{solute}} & = \frac{mass_{\text{solute}}}{MM_{\text{solute}}} \\ & = \frac{\text{4 g}}{\text{40 g/mol}} \\ & = \text{0.1 mol} \end{aligned}[/tex]
Step 2: Calculate the molarity of solution.
The volume of solution must be expressed in liters. Thus, 200 mL = 0.2 L
[tex]\begin{aligned} M & = \frac{n_{\text{solute}}}{V_{\text{solution}}} \\ & = \frac{\text{0.1 mol}}{\text{0.2 L}} \\ & = \text{0.5 mol/L} \\ & = \boxed{0.5 \: M} \end{aligned}[/tex]
Hence, the molarity of 4 g caustic soda dissolved in 200 mL of solution is 0.5 M.
[tex]\\[/tex]
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