If the air temperature is 20 degree Celsius, how much water it holds at 100% relative humidity? If the absolute humidity 10 gram per kg of air. What is the relative humidity. Show working out

Let's calculate the humidity values.

1. Water held at 100% relative humidity at 20°C At $20^\circ\text{C}$, the maximum amount of water vapor that $1 \text{ kg}$ of air can hold (saturation mixing ratio) is approximately $14.7 \text{ grams}$. This value is obtained from psychrometric charts or standard tables for saturated air.

$\boxed{\text{14.7 grams of water per kg of air}}$

2. Calculate relative humidity Relative humidity (RH) is the ratio of the absolute humidity (actual water vapor content) to the saturation humidity (maximum water vapor content at that temperature), expressed as a percentage.

Step 1: Identify the given values. Absolute humidity = $10 \text{ g/kg of air}$ Saturation humidity at $20^\circ\text{C}$ = $14.7 \text{ g/kg of air}$ (from part 1)

Step 2: Apply the relative humidity formula. $\text{Relative Humidity} = \frac{\text{Absolute Humidity}}{\text{Saturation Humidity}} \times 100\%$ $\text{Relative Humidity} = \frac{10 \text{ g/kg}}{14.7 \text{ g/kg}} \times 100\%$ $\text{Relative Humidity} \approx 0.68027 \times 100\%$ $\text{Relative Humidity} \approx \boxed{\text{68.0\%}}$