Answer: The correct option is ALL OF THE ABOVE.
Explanation:
TITRATION is a type of volumetric analysis which is used for determining the concentration of solutions. In this process a specific volume of a solution is placed in a conical flask by means of a pipette and small quantities of a second solution is slowly added from a burette until the end point is reached. This is determined by a means of an indicator which shows a characteristic colour change.
During titration, the following precautions should be followed to avoid errors and maintain standardisation in the experiment.
--> Any air bubble in the burette and pipette must be removed during measurement
--> the burette tap should be tightened to avoid leakage.
--> Remove the funnel from the burette before taking any reading to avoid errors in reading the volume.
--> use the base solution such as Sodium Hydroxide Solution to rinse the burette after washing with soap and tap water:
• to remove any air bubble and fill it's tip
• to remove any residual liquid from the water and soap solution which may interfere with the results of the experiment.
• to check if the burette is in good condition.
Therefore all of the above options to the question are correct.
Answer:
Work done = 600 J
Power used = 60 W
Explanation:
Given:
Force acting on the box is, 
Displacement of the box is, 
Time taken for the work, 
Now, we know that, work is said to be done by a force only when there is displacement caused by the force in its direction.
Here, the force acting on the box causes a displacement of 30 m in its direction. So, work done is equal to the product of force and displacement caused.
Therefore, work done on the box is given as:

Therefore, the work done is 600 J.
Now, we know that, power is given as work done per unit time.
So, power used is given as:

Therefore, the power used is 60 W.
For this problem, we use Graham's Effusion Law to find out the rate of effusion of chlorine gas. The formula is as follows:
R₁/R₂ = √(M₂/M₁)
Let 1 be N₂ while 2 be Cl₂
255/R₂ = √(28/70.8)
Solving for R₂,
R₂ = 405.5 s
<em>Thus, it would take 405.5 s to effuse chlorine gas.</em>
The basic building block of matter is the atom.