Tag: intermolecular forces: cohesive and adhesive forces

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Multiple choice intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

The dimension of sphere of influence of an molecules is

  1. $1 A^o$

  2. $10 A^o$

  3. $100 A^o$

  4. $0.1 A^o$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation


The Molecular range is the radius around a molecule in a substance to which the molecule can exert attraction force on another molecule$.$  This is distance$,$
Sphere of influence is the spherical space/volume around a molecule in a substance$,$ inside which the molecule at center can exert attractive force on another molecule$.$
The molecular range is very small like $1 nanometer.$
Surface tension is the surface energy $-$ additional energy required to increase surface by a unit area$.$  This is also the tension force exerted $($along the line$)$ on the boundary of a surface per unit length$.$
Hence,
option $(A)$ is correct answer.
Multiple choice intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

If $2$ bubble of radius $r _1$ & $r _2$ are combined then find radius of common surface.

  1. $\dfrac{r _1r _2}{r _1+r _2}$

  2. $\dfrac{r _1r _2}{r _1-r _2}$

  3. $\sqrt{r _1r _2}$

  4. $\dfrac{r _1+r _2}{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When two bubbles of radii r1 and r2 are joined, the radius of the common interface r is given by 1/r = 1/r1 - 1/r2 (assuming r1 < r2). Thus, r = (r1 * r2) / (r2 - r1).

Multiple choice intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

On a clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because

  1. mercury is a metal

  2. density of mercury is greater than that of water

  3. cohesion of mercury is greater than its adhesion with glass

  4. cohesion of water is greater than its adhesion with glass
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Mercury remains spherical on a glass plate due to greater cohesive force between mercury molecules than adhesive force between mercury and glass plate.

Multiple choice intermolecular forces: cohesive and adhesive forces surface tension properties of matter physics

A capillary tube of radius $0.25\ mm$ is submerged vertically in water so that $25\ mm$ of its length outside water. The radius of curvature of the meniscus will be $(T = 7.5\times 10^{-3} N/m)$.

  1. $0.2\ mm$

  2. $0.4\ mm$

  3. $0.6\ mm$

  4. $0.8\ mm$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$h= \dfrac{2T}{dgx}$

$h= \dfrac{2\times 7.5 \times {10}^-3} {1000 \times 10 \times d}$
$h=25mm$
$d= 0.6 mm$