You calibrate 25ml pipette at 25degae centigrade using steel weight.the weight of the delivered volume of water is 24.971.what is the volume of pipette at 20 and 25 degree centigrade?
To determine the volume of the pipette at different temperatures, you need to take into account the coefficient of expansion for both the pipette and the water being used.
The coefficient of expansion for the pipette is typically provided by the manufacturer. Let's assume it is given as 0.00011 per degree Celsius.
1. Calculate the expansion of the pipette from 25°C to 20°C:
- Temperature difference: 25°C - 20°C = 5°C
- Expansion of the pipette: 25 ml x 0.00011/°C x 5°C = 0.01375 ml
- Volume of the pipette at 20°C: 25 ml - 0.01375 ml = 24.98625 ml
So, the volume of the pipette at 20 degrees Celsius is approximately 24.986 ml.
2. Calculate the expansion of the water from 25°C to 20°C:
- Expansion coefficient of water: 0.00021 per degree Celsius (approximately)
- Temperature difference: 25°C - 20°C = 5°C
- Expansion of water: 24.971 g x 0.00021/°C x 5°C = 0.026127 g
- Convert the expansion in weight to volume using water's density (assumed to be 1 g/ml):
0.026127 g ÷ 1 g/ml = 0.026127 ml
- Effective volume of the water at 25°C: 24.971 ml - 0.026127 ml = 24.944873 ml
So, the effective volume of the water at 20 degrees Celsius is approximately 24.945 ml.
Note: The values used for coefficient of expansion for both the pipette and water are approximations. It's always best to refer to the manufacturer's specifications for accurate values.