The density of $\mathrm{NaOH}$ solution is $1.2 \mathrm{~g} \mathrm{~cm}^{-3}$. The molality of this solution is________ $\mathrm{m}$.
(Round off to the Nearest Integer)
[Use : Atomic masses : $\mathrm{Na}: 23.0 \mathrm{u} \quad \mathrm{O}: 16.0 \mathrm{u}$ $\mathrm{H}: 1.0 \mathrm{u}$
Density of $\mathrm{H}_{2} \mathrm{O}: 1.0 \mathrm{~g} \mathrm{~cm}^{-3}$ ]
Consider $1 \ell$ solution
mass of solution $=(1.2 \times 1000) \mathrm{g}$
$=1200 \mathrm{gm}$
Neglecting volume of $\mathrm{NaOH}$
Mass of water $=1000 \mathrm{gm}$
$\Rightarrow$ Mass of $\mathrm{NaOH}=(1200-1000) \mathrm{gm}$
$=200 \mathrm{gm}$
$\Rightarrow$ Moles of $\mathrm{NaOH}=\frac{200 \mathrm{~g}}{50 \mathrm{~g} / \mathrm{mol}}=5 \mathrm{~mol}$
$\Rightarrow$ molality $=\frac{5 \mathrm{~mol}}{1 \mathrm{~kg}}=5 \mathrm{~m}$
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All Study Material
- JEE Main
- Exam Pattern
- Previous Year Papers
- PYQ Chapterwise
- Physics
- Kinematics 1D
- Kinemetics 2D
- Friction
- Work, Power, Energy
- Centre of Mass and Collision
- Rotational Dynamics
- Gravitation
- Calorimetry
- Elasticity
- Thermal Expansion
- Heat Transfer
- Kinetic Theory of Gases
- Thermodynamics
- Simple Harmonic Motion
- Wave on String
- Sound waves
- Fluid Mechanics
- Electrostatics
- Current Electricity
- Capacitor
- Magnetism and Matter
- Electromagnetic Induction
- Atomic Structure
- Dual Nature of Matter
- Nuclear Physics
- Radioactivity
- Semiconductors
- Communication System
- Error in Measurement & instruments
- Alternating Current
- Electromagnetic Waves
- Wave Optics
- X-Rays
- All Subjects
- Physics
- Motion in a Plane
- Law of Motion
- Work, Energy and Power
- Systems of Particles and Rotational Motion
- Gravitation
- Mechanical Properties of Solids
- Mechanical Properties of Fluids
- Thermal Properties of matter
- Thermodynamics
- Kinetic Theory
- Oscillations
- Waves
- Electric Charge and Fields
- Electrostatic Potential and Capacitance
- Current Electricity
- Thermoelectric Effects of Electric Current
- Heating Effects of Electric Current
- Moving Charges and Magnetism
- Magnetism and Matter
- Electromagnetic Induction
- Alternating Current
- Electromagnetic Wave
- Ray Optics and Optical Instruments
- Wave Optics
- Dual Nature of Radiation and Matter
- Atoms
- Nuclei
- Semiconductor Electronics: Materials, Devices and Simple Circuits.
- Chemical Effects of Electric Current,