Using appropriate enthalpy of formation data from the 'properties of inorganic compounds' table in SICD calculate ÎsolHm for CaCl2. Would you expect ÎsolHm of CaCl2 to be the same as that for CaCl2.6H2O? Explain. (Note that this is not a question about measuring ÎsolHm, but it asks if ÎsolHm will be the same or different for these two substances. If your answer involves heat capacities or temperature differences you are missing the point.)

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18 Nov 2019

Using appropriate enthalpy of formation data from the 'properties of inorganic compounds' table in SICD calculate Î_solH_m for CaCl₂.
Would you expect Î_solH_m of CaCl₂ to be the same as that for CaCl₂.6H₂O? Explain. (Note that this is not a question about measuring Î_solH_m, but it asks if Î_solH_m will be the same or different for these two substances. If your answer involves heat capacities or temperature differences you are missing the point.)

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Heat, q, is energy transferred between a system and its surroundings. For a process that involves a temperature change

q=mâ Csâ ÎT

where Cs is specific heat and m is mass.

Heat can also be transferred at a constant temperature when there is a change in state. For a process that involves a phase change

q=nâ ÎH

where, n is the number of moles and ÎH is the enthalpy of fusion, vaporization, or sublimation.

The following table provides the specific heat and enthalpy changes for water and ice.

Substance	Specific heat [J/(gâ âC)]	ÎH (kJ/mol)
water	4.18	44.0
ice	2.01	6.01

Part A

Calculate the enthalpy change, ÎH, for the process in which 45.7 g of water is converted from liquid at 10.1 âC to vapor at 25.0 âC .

For water, ÎHvap = 44.0 kJ/mol at 25.0 âC and Cs = 4.18 J/(gâ âC) for H2O(l).

Part B

How many grams of ice at -12.5 âC can be completely converted to liquid at 8.1 âC if the available heat for this process is 5.27Ã10³ kJ ?

For ice, use a specific heat of 2.01 J/(gâ âC) and ÎHfus=6.01kJ/mol.

Express your answer to three significant figures and include the appropriate units.

so I have following data but I don't know how to calculateforq

temperature of HCL 22.2 C

temperature of NaOH 21.9 C

Final temperature of resulting salt solution (Tf) 22.6 C

what is delta T? and after that how do you calculate molesofNaOH or HCL netrualized (moles of rxn)

also how do u calculate:

Enthalpy change (using expt data) for OH- + H+ --->H2O(l)

standard enthalpy of formation H2O

Calculated enthalpy of formation of OH-

please help me!!

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Hello guys. I have to do these calculations but I can seemtodo it and I am stuck. So can someone please help me calculatethesevalues?

We know that the specific heat of water (same for solutionforthis expt) is 4.18 J/g C

and densities of all solutions are 1.00 g/mL

Temp of HCl: 22.2 C

Temp of NaOH: 22.0 C

so initial Temp is average of those two which is 22.1 C

final temperature of the resulting salt solution: 22.6

ÎT= 22.6 - 22.1 = 0.5 C

so q = (100)(4.18)(0.5)

q= 209 J

so q _rxn = -q _soln

so =209 J

ok now how do you calculate moles of NaOH or HCLneutralized (molesof rxn)

once we get moles of rxn we can calculate theenthalpyof neutralization of rxn

which is calculated by q_rxn/(molesofrxn)

so how do you calculate:

enthalpy change (using expt data) for OH^-+H⁺ -> H₂O _(l)

standard enthalpy for formation H2O_(l)(ÎH)

calculated enthalpy for formation OH-_(aq)(ÎH)

Photosynthesis is the process by which plants effectively capture energy from the sun and store it for later use by organisms. It's the fundamental process that enables the entire food chain. Actual photosynthesis is a highly complex process involving many steps and many different chemicals, but we can get an idea of what's happening to thermodynamic quantities (enthalpy, Gibbs free energy, and entropy) using simpler reactions.

Let's consider a toy model in which an input of energy (for example from the sun) is be used to combine water and carbon dioxide to create an organic molecule (formaldehyde) and oxygen, effectively "storing" that energy for use later. The simplest possible such process is given by:

CO₂ + H₂O â O₂ + CH₂O

The table lists the enthalpy of formation, ÎH_f and the entropy S for 1 mol of each of the substances involved in this reaction at 298 K and 10⁵ Pa.

	ÎH_f (kJ)	S (kJ/K)
CH₂O	-115.9	0.2189
H₂O	-241.82	0.1888
CO₂	-393.51	0.2138
O₂	0	0.2051

Answer the following questions assuming that 1 mol of formaldehyde molecules are formed.

1. What is the change in enthalpy of this reaction?
ÎH = ____ kJ

Does this change in enthalpy represent energy that must be added to the system, or energy that is released from the system?
-Energy must be added or Energy is released?

2. What is the change in entropy for this reaction?
ÎS = ____ kJ/K

Does the entropy increase or decrease?
-Entropy increases or Entropy decreases?

At 298 K, what is the heat transfer that corresponds to this change in entropy?
Q = ____ kJ
Does this heat transfer represent energy that is added to the system, or energy that is released from the system?
--Energy is added Energy is released ?

3. What is the change in Gibbs free energy for this reaction?
ÎG = _____ kJ

The Gibbs free energies of formation, ÎG_f, are: -228.57 kJ for water; -394.36 kJ for CO₂; and 0 kJ for O₂. What is the Gibbs free energy of formation for formaldehyde?
ÎG_f (formaldehyde) = _______ kJ

4. Using the formation of formaldehyde as a model, comment on photosynthesis and the formation of sugars using what we know about entropy and free energy.

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