Physical Chemistry Answers

What is the freezing point and boiling point of a solution with 474.3 g of Al[sub]2[/sub](SO[sub]4[/sub])[sub]3[/sub] dissolved in 325 g of water?

Consider the compression at 15.6& [sup]o[/sup]C of 0.35 mol H[sub]2[/sub]O(l) from 0.10 atm to1.00 atm. Calculate the values of ΔG when the process is carried out:
(a) isothermally and reversibly and
(b) isothermally and irreversibly under a constantexternal pressure of 1.0 atm.

Q. Find energy of each of the photons which:-
(i) correspond to light of frequency 3 x 10^15 Hz.
(ii) Have wavelength of 0.50A

The equation of reaction between potassium and water.

2K + 2H[sub]2[/sub]O(1) --> 2KOH(aq) + H[sub]2 [/sub]
Find the mass of potassium needed to produce 1.505 x 10[sup]24[/sup] hydorgen molecule.

What's the empirical formula of a molecule containing 65.5% carbon, 5.5% hydrogen and 29.0% oxygen?

1.6 g ( an excess) of Mg was added to 100 cm[sup]3[/sup] of 2.0 mol dm[sup]–3[/sup] CuSO4(aq). The temperature rose from 20C to 65C (45’C rise). Find ΔHr for the reaction: (c = 4.2 J g[sup]-1[/sup] K[sup]-1[/sup])
Mg(s) + CuSO[sub]4[/sub](aq) --> MgSO[sub]4[/sub](aq) + Cu(s)

Find the energy change by using ΔH = - mcΔT
(MY ANSWER) 100 x 4.2 x 45 = 18900 J mol[sup]-1[/sup] = 18.9 kJ mol[sup]-1[/sup] (which is correct)

Find how many moles reacted (n)
(MY ANSWER) 1.6/159.6 = 0.01 then 0.01/2 = 0.005 (which is incorrect, correctly should be 2x100/1000; do not know how!)

Scale the quantities for the combustion of 1 mole (ΔH/n)
18.9/0.005 = -3780 kJ mol[sup]-1[/sup] (using the previous incorrect figure this is also wrong)

Could you please help to explain step 2?

Three helium nuclei fuse together, forming one carbon nucleus. The mass of carbon is less than
three times the mass of helium. When helium fuses into carbon, which of the following occurs?
a. Rest‐mass energy is converted into some other form of energy
b. Some other form of energy is converted into rest‐mass energy
c. The chemical reaction changed the total mass
d. The mass of three helium nuclei turned into one carbon nucleus and other smaller
particles, such as protons and neutrons.

The osmotic pressure of an aqueous solution of urea at 300 K is 120 kPa. Calculate the freezing point of the same solution.

I have a lab experiment where I mix a sample of unknown K[sub]2[/sub]C[sub]2[/sub]O[sub]4[/sub] with 25mL of H[sub]2[/sub]SO[sub]4[/sub] and 25mL of H[sub]2[/sub]O before titrating it with KMnO[sub]4[/sub]. My question is, if the sample of unknown K[sub]2[/sub]C[sub]2[/sub]O[sub]4[/sub] composition was not mixed well before the titration, how would this effect my results?

One mole of an ideal gas is expanded reversibly and isothermally from 12 bar to 1 bar at 298.15K. Calculate w, q, dU and dH