a student burns a peanut in a calorimeter. she places 10 ml of water in a test tube. she weighs a peanut before and after burning it. It weighs 3 grams before and 1 gram after burning. She determines that the temperature was at 20 degrees C before and 70 degrees C afterwards. How many kcals/g did the peanut contain?
It isn't clear to me what the problem is all about. Is the water in the test tube in the calorimeter or is that separate?
To determine the energy content of the peanut in kcal/g, we can use the formula:
Energy content = (Temperature change) x (Volume of water) x (Specific heat capacity of water) / (Change in mass of the peanut)
Let's calculate the variables step by step:
1. Temperature change = Final temperature - Initial temperature
= 70 °C - 20 °C = 50 °C
2. Volume of water = 10 ml = 10 g (since the density of water is approximately 1 g/ml)
3. Specific heat capacity of water = 1 calorie/g°C (or 1 kcal/kg°C)
4. Change in mass of the peanut = Initial mass - Final mass
= 3 g - 1 g = 2 g
Now, plug these values into the formula:
Energy content = (50 °C) x (10 g) x (1 calorie/g°C) / (2 g)
= 250 calories / 2 g
= 125 calories/g
So, the peanut contained approximately 125 calories per gram (kcal/g).