Can someone make sure I did this write!
What is the molar change in enthalpy when 100 g of ice is heated from -18.2 C to -72 C (Cp = 37.4 J/K*mol)
100g of ice = 100 g/-18.2 C = 5.56 mol
5.56 mol * 37.4 J/K * mol * 53.8 K = 1118 J
I would have used 100 g/18.015 = 5.55 moles (You seem to have picked up the 18.2 from the degrees C).
Then 5.55 x 37.4 x 53.8 = 11,167 Joules.
Did you just drop the last digit?
THANK YOU! yes, i got 11180, i see what I did wrong.
By the way, I'm a little confused with the statement that ice is heated to move it from -18.2 to -72.
To calculate the molar change in enthalpy, you need to use the given heat capacity value (Cp = 37.4 J/K*mol) and the temperature difference (initial and final temperatures).
Here is a step-by-step explanation of how to solve the problem:
1. First, convert the mass of ice from grams to moles. The molar mass of water (H2O) is approximately 18 g/mol. Therefore, 100 g of ice is equal to 100 g / 18 g/mol = 5.56 moles.
2. Next, calculate the temperature difference by subtracting the initial temperature from the final temperature. In this case, the initial temperature is -18.2 °C and the final temperature is -72 °C. Therefore, the temperature difference is: -72 °C - (-18.2 °C) = -53.8 °C.
3. Now, multiply the number of moles by the heat capacity and the temperature difference to find the molar change in enthalpy. The equation is: molar change in enthalpy = number of moles * heat capacity * temperature difference.
Plugging in the values, we have:
molar change in enthalpy = 5.56 mol * 37.4 J/K*mol * 53.8 K = 1118 J.
So, the molar change in enthalpy when 100 g of ice is heated from -18.2 °C to -72 °C is 1118 J.