A 4.5 g sample of glucose, a carbohydrate, is placed in a calorimeter. The water in the container has a mass of 1500 g and an initial temperature of 15°C. After all the glucose is burned, the water temperature is 27 °C. What is the caloric value for glucose?
Answer: _____________ kcal/g of glucose
First find the heat the water gained....( q = sp ht × mass × ΔT ) but this value will be for the 4.5 g sample of glucose.....you are asked for kcal per gram of glucose......also, when determining the heat the water gains, the mass will be 1500 g, referring only to the mass of the water.
q for water = 1500 g x 1 cal/g x (27-15) = 18,000 cal or 18 kcal.
That's the heat generated for 4.5 g glucose. So 18 kcal/4.5 g = q for sugar/gram. I found the value of 15.6 kJ/g and those are close. You cana convert 15.6 kJ x 1 kcal/4.184 kJ = ? kcal
To solve this problem, we need to calculate the heat gained by the water in the calorimeter when the glucose is burned. The heat gained can be calculated using the formula:
q = sp ht × mass × ΔT
Where:
q = heat gained by the water
sp ht = specific heat capacity of water (which is approximately 4.18 J/g°C)
mass = mass of water (1500 g)
ΔT = change in temperature (27°C - 15°C = 12°C)
Substituting the values into the formula:
q = 4.18 J/g°C × 1500 g × 12°C
q = 75,240 J
Now, we need to convert this value from joules to kilocalories (kcal).
To do this, we need to know the conversion factor: 1 kilocalorie (kcal) = 4184 joules (J).
So, dividing the heat gained by the conversion factor:
q = 75,240 J ÷ 4184 J/kcal
q ≈ 18 kcal
To find the caloric value for glucose, we need to divide the heat gained (18 kcal) by the mass of glucose (4.5 g):
Caloric value of glucose = 18 kcal ÷ 4.5 g
Caloric value of glucose ≈ 4 kcal/g
Therefore, the caloric value for glucose is approximately 4 kcal/g.