CHEMISTRY MASTER SOLVER PRO Question Calculate the molarity of a solution containing 5 g NaOH in 250 mL of solution. Detail Level: High School Solution Style: Numerical Solution --- Question Type Physical Chemistry – Numerical (Concentration of Solutions) --- Problem Analysis Given: Mass of NaOH = 5 g Volume of solution = 250 mL = 0.250 L Required: Molarity (M) of the NaOH solution. --- Key Concepts Molarity (M) Molarity is defined as the number of moles of solute present in 1 litre of solution. \boxed{M=\frac{\text{Number of moles of solute}}{\text{Volume of solution (L)}}} Number of Moles \boxed{\text{Moles}=\frac{\text{Mass}}{\text{Molar Mass}}} --- Chemical Information Sodium Hydroxide Chemical Formula: \mathrm{NaOH} Molar Mass: Na = 23 g/mol O = 16 g/mol H = 1 g/mol 23+16+1=40\ \text{g/mol} Therefore, \boxed{\text{Molar Mass of NaOH}=40\ \text{g/mol}} --- Step-by-Step Solution Step 1: Calculate the number of moles \text{Moles}=\frac{5}{40} =0.125\ \text{mol} --- Step 2: Convert volume into litres 250\ \text{mL}=\frac{250}{1000}=0.250\ \text{L} --- Step 3: Calculate molarity M=\frac{0.125}{0.250} M=0.50\ \text{mol L}^{-1} or \boxed{M=0.50\ \text{M}} --- Calculations Summary Quantity Value Mass of NaOH 5 g Molar mass 40 g/mol Moles 0.125 mol Volume 0.250 L Molarity 0.50 M --- Units & Significant Figures Mass → grams (g) Volume → litres (L) Amount of substance → moles (mol) Molarity → mol L⁻¹ (M) Using the given data, the answer is appropriately reported as: \boxed{0.50\ \text{M}} --- Chemical Equation (Relevant Property) NaOH dissociates completely in water: \boxed{\mathrm{NaOH(aq)\rightarrow Na^+(aq)+OH^-(aq)}} This is a balanced equation showing NaOH as a strong electrolyte. --- Final Answer \boxed{\text{The molarity of the NaOH solution is }0.50\ \text{M}.} --- Exam Tips Always convert mL to L before using the molarity formula. Remember the formula: \boxed{M=\frac{\text{moles}}{\text{volume in litres}}} \boxed{\text{Moles}=\frac{\text{Mass}}{\text{Molar Mass}}} --- Common Mistakes ❌ Using volume in mL instead of L. ❌ Using the wrong molar mass of NaOH. ❌ Confusing molarity (M) with molality (m). --- Memory Tip "Molarity = Moles per Litre" Think M = Mole ÷ Litre. --- Real-World Application Molarity is widely used to prepare laboratory solutions, perform acid–base titrations, manufacture chemicals, and calculate reagent concentrations in industrial and research laboratories.