A volume of 585 ml of 1%(w/w) NaCl solution of density 1.2 g/ml is required for complete coagulation — Surface Chemistry Chemistry Question

💡 Solution & Explanation

Coagulation value is defined as the minimum concentration of an electrolyte in millimoles per litre (mmol/L) of sol required to cause coagulation in 2 hours. Mass of NaCl solution = Volume × density = 585 ml × 1.2 g/ml = 702 g. Mass of NaCl in it = 1% of 702 g = 7.02 g. Moles of NaCl = 7.02 g / 58.5 g/mol = 0.12 mol = 120 mmol. This 120 mmol is required to coagulate 200 ml of gold sol. The amount required for 1000 ml (1 L) of sol = (120 mmol / 200 ml) × 1000 ml = 600 mmol. The coagulation value is 600. Therefore, correct answer is 0600.