# Estimate the Mass of Urea- Required in Making 2.5 Kg of 0.25 Molal Aqueous Solution: Urea (For CBSE, ICSE, IAS, NET, NRA 2022)

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## Urea

• Urea is a nitrogenous compound containing a carbonyl group attached to two amine groups with osmotic diuretic activity.
• Urea, also called carbamide, the diamide of carbonic acid.
• Its formula is
• Urea has important uses as a fertilizer and feed supplement, as well as a starting material for the manufacture of plastics and drugs.
• A colourless, crystalline substance melts at and decomposes before boiling.
• Urea is used to treat dry/rough skin conditions (e. g. , eczema, psoriasis, corns, and callus) and some nail problems (e. g. , ingrown nails) .
• It may also be used to help remove dead tissue in some wounds to help wound healing.

## Molality

= molality

Mol = moles of solute

Kg = kilograms of solvent

• Molality is a property of a solution and is defined as the number of moles of solute per kilogram of solvent.
• Molality is a measure of number of moles of solute present in 1 kg of solvent.
• This contrasts with the definition of molarity which is based on a specified volume of solution.
• A commonly used unit for molality in chemistry is mol/kg. A solution of concentration 1 mol/kg is also sometimes denoted as 1 molal.
• The SI unit for molality is mol/kg. A solution with a molality of 3 mol/kg is often described as β3 molalβ or β3 m.β
• So, following the SI system of units, mol/kg or a related SI unit is now preferred.

## Mass of Urea

• Mass of solution = 2.5 Kg
• Molality = 0.25 m
• Molar mass of urea ()

• Mass of urea = Number of moles of urea Γ Molar mass of urea
• Mass of 0.25 moles of urea
• Mass of solution = 1000 g + 15 g = 1015 g
• 1015 g of aqueous solution contains urea

β΄ 2500 g of aqueous solution will require urea

Mass of urea required in making 25 grams of 0.25 m = 37 grams

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