Tia has a sample of pure gold (Au). She weighed the sample and the result was 12.6 grams. Tia wants to determine the number of atoms in the sample. Calculate the number of atoms in 12.6 g of pure gold.

How would I separate and purify 2 out of 3 of: 50% o-toluic acid, 40% fluorene, and 10% 1,4-dibromobenzene, using any of the following: 1M NaOH, 6M NaOH, 1M HCl, 1M NaHCO3, saturated sodium chloride, diethyl ether, 95% ethanol, methanol, alcohol, acetone, hexane, toluene, methylene chloride, or granular anhydrous sodium sulfate?

The decomposition of ozone into oxygen is believed to occur by the following mechanism:

O₃   <-->   O₂ + O       fast, equilibrium

O +   O₃ --> 2 O₂       slow

The rate constant for the overall rate law is 30.6 at 87^oC. If you start with a mixture of 1.5 M O₃ and 3.0 M O₂, what is the initial rate of the reaction?

1.Calculate the pH of a solution obtained by mixing 100 ml of 1 M HEPES and 25 ml of 1 M NaOH and adjusting the volume to one liter with water.

2. Calculate the pH of a solution obtained by mixing 100 ml of 1 M NH3 (pKa 9.25) and 60 ml of 1 M HCl and adjusting the volume to one liter with water. (Answer 9.07)

I want to know the specific calculation to get a final answer. Thank you.

For each of the following compounds, predict the energy barrier to rotation (looking down any one of the C-C bonds 2,2-dimethylpropane & 2-methylpropane

2H₂S (g) = 2H₂ (g) + S₂ (g)

When heated hydrogen sulfide gas decomposes according to the equation above. A 3.40g smple of H₂S(g) is introduced into an evacuated rigid 1.25 L container. The sealed container is heated to 483 K, and 3.72 x10^-2 mol of S₂ (g) is present at equilibrium.

a) Write the expression for the equilibrium constant, K_c for the decomposition reaction represented above.

b) Calculate the equilibrium concentration in M of H₂ (g) and H₂S (g) in the container 483 K

c) Calculate the value of the equilibrium constant K_c for the decomposition reaction of 483K

Calculate the hydroxide ion concentration in a 0.0500 M NaOCl solution. The acid dissociation constant for HOCl is 3.0 x 10^-8.

What mass of hydrochloric acid (in grams) can be neutralized by 2.2 g of sodium bicarbonate? (Hint: Begin by writing a balanced equation for the reaction between aqueous sodium bicarbonate and aqueous hydrochloric acid.)

A phosphate buffer contains 0.075M K₂HPO₄ and 0.125M KH₂PO₄. pKa values for H₃PO₄ are 2, 6.8, and 12.2. Calculate the concentrations of:

1.) H₂PO₄^- concentration

2.) H⁺ concentration

In what direction will the water activity of a liquid food change (higher, lower, or virtually unaltered) if the following changes occur, keeping other factors constant? In each case give an explanation.

1. Addition of sodium chloride

2. Addition of native starch (granules)

3. Heating the food with starch and cooling again to the original temperature without loss of water

4. Enzymatic hydrolysis of the protein present

5. Emulsifying oil into it

6. Freezing part of the water

Three moles of an ideal gas expand isothermally and reversibly from 90 to 300 L at 300 K.

a) Calculate ΔUm, ΔSm, w per mole, and q per mole.

b) If the expansion is carried out irreversibly by allowing the gas to expand rapidly into a vacuum, determine ΔUm, ΔSm, w per mole, and q per mole

You work in a medical research lab with a biochemist who asks you to make a 1.00 L phosphate buffer stock solution with pH = 7.4. The total phosphorus concentration is to be 0.250 M. In the storeroom, there are the following reagents: (1) a 3.00 M phosphoric acid stock solution, (2) solid sodium dihydrogen phosphate, (3) solid sodium monohydrogen phosphate, (4) solid, sodium phosphate, (5) a 3.00 M HCl(aq) stock solution, (6) a 3.00 M NaOH(aq) stock solution, and (7) deionized water.

(i) (2 pts) To make an optimum buffer, it is important that the pKa of the acid part is close to the target pH of the buffer. Which phosphate species has a pKa value closest to pH = 7.4?

(ii) (4 pts) Choose this phosphate species (in i) as the only phosphorus component. What amounts of this substance and any other reagents (grams of solid(s); mL of any solution(s) and water) would you need to make the buffer with pH = 7.4?

(iii)(4 pts) Choose this phosphate species (in i) and either its conjugate acid or base as the only two phosphorus components. What amounts of this substance, its conjugate acid or base, and water (grams of solid(s); mL of any solution(s) and water) would you need to make the buffer with pH = 7.4?

Why can the Drude equation not be applied in the range of wavelengths near maximum absorbance?

An antifreeze protein, with a molecular weight of 17000 Da, was found to be present at a concentration of 10g dm-3 in the serum of an Antarctic fish. calculate the expected depression of the freezing point and compare your result with 1) the observed depression of 0.6K and 2) the depression of 0.0014K observed for 10g dm-3 solution of lysozyme, molecular weight of 14500 Da. for pure water, Lf=6.02kj ml-1 and Tm=273.15 K