SME
Grade 12 Science · Problem type
Relative humidity
Use this for “Air holds 6 g of water vapor per kg and could hold 15 g. What is its relative humidity?”
Diagram
40% of 15 g/kg is 6 g/kg.
This is an example. Type your own values to start a new problem.
RH
%
=
w (g/kg)
÷
wₛ (g/kg)
×
100
Formulas
RH
=
w
wₛ
×
100
40
=
6
15
×
100
Assumptions
•
Warm air can hold more water vapor than cold air.
•
Cooling the air raises RH without adding water.
•
At 100 % the air is at its dew point.
Step-by-step
WE KNOW
w = 6 g/kg, wₛ = 15 g/kg
FIND
relative humidity (RH)
Step 1 · Find relative humidity (RH)
Use RH = w ÷ wₛ × 100
The vapor the air holds as a percent of what it could hold.
RH
=
6
15
×
100
RH = 0.4 × 100
RH = 40%
Check
Put the numbers back in. Both sides should match.
40
=
6
15
×
100
✓
Topic check
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