Question

What is the SI unit for rate of diffusion?

• A. $cm^3~minute^{-1}$
• B. $dm^3~hour^{-1}$
• C. $dm^3~s^{-1}$
• D. $mL~hour^{-1}$

Hint:

Rate quantities generally have units: \[ \frac{\text{quantity}}{\text{time}} \] For diffusion: \[ \frac{\text{volume}}{\text{time}} \]

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The rate of diffusion refers to the amount of substance (usually gas) that moves or spreads per unit of time.
Mathematically, it is expressed as the volume of gas diffused divided by the time taken.
Step 2: Detailed Explanation:
In the International System of Units (SI):
- The unit for time is the second (\(s\)).
- The standard unit for volume is the cubic meter (\(m^3\)).

However, in practical laboratory chemistry, volume is frequently measured in decimeters cubed (\(dm^3\)), which is equivalent to one liter (\(L\)). The \(dm^3\) is a recognized SI-derived unit.
Therefore, the rate (Volume / Time) would naturally be in units of \(dm^3\) per second, or \(dm^3\text{ s}^{-1}\).

Evaluating the options:
- Minutes and hours are not the base SI units for time.
- \(cm^3\) and \(mL\) are sub-multiples of volume units, but \(dm^3\) is the standard derivation used alongside molarity and gas laws in SI conventions.
Step 3: Final Answer:
The correct unit is \(dm^3\text{ s}^{-1}\).