hemistry 1215, Experiment #12; Determination of the Atomic Weight of an Unknown Metal, Post-lab Name ____________________________________ 1. A student who was measuring the atomic weight of a metal failed to thoroughly clean her metal ribbon leaving an oxide coat on the metal. Will the volume of hydrogen gas generated be lower or higher than the true value? 2. What volume will 5.00 g of helium gas occupy at 0.800 atmospheres and 25 o C? 3. Use Dalton’s law of partial pressures to calculate the pressure of hydrogen gas collected over water if the ambient pressure is 710 mm Hg and the temperature is 25o C. 4. A student didn’t equalize the water levels inside the eudiometer tube with that of his water bath. The water level inside the tube was 10 cm higher than the water level outside the tube. He ignored the difference and proceeded with his calculations. What effect will this error have on his calculated atomic mass? Explain your rationale.

Determine the mass (in g) of sodium hydrogen phosphate (Na₂HPO₄) that must be added to 87.8 mL of 0.0264 M sodium dihydrogen phosphate to yield a pH of 7.78. Report your answer to 3 significant figures.

Assume the volume of the solution does not change and that the 5% approximation is valid.

How much heat (in kJ) is required to warm 13.0 g of ice, initially at -13.0 ∘C, to steam at 113.0 ∘C? The heat capacity of ice is 2.09 J/g⋅∘C and that of steam is 2.01 J/g⋅∘C.

TRUE or FALSE? Please explain each answer!

a) The more negative the ∆H value of a reaction the faster it is.

b) The more negative the ∆G value of a reaction the faster it is.

c) If you compare two reactions, the one with the lowest activation energy is faster (tricky!)

d) A catalyst is a substance that lowers the ∆G value of a reaction so it becomes more spontaneous.

e)Enzymes are proteins that lower the activation energies of reactions in the cell.

f) ATP hydrolysis is thermodynamically favorable but the reaction is slow in the absence of the enzyme specialized in catalyzing this reaction.

Calculate the pH of the following:

a) 0.25 M HClO (aq)
b) 0.015 M Sr (OH) (aq)
c) 0.015 M Hl (aq)
d) 0.15 M CH3NH2 (aq)

25 pts) One mole of ideal, monatomic gas, initially at T = 250 K and pressure 5.0 atm is: a) reversibly heated at constant pressure until its volume doubles b) reversibly heated at constant volume until its pressure doubles Determine w, q ,ΔU, ΔΗ , and ΔS for these two cases (20 pts). Can you calculate A and G for these two cases? Explain why. (5 pts)

How would I calculate the final concentration of each anion solution after equal amounts are combined to make 1 mL of the known solution. Anions are 0.20M of NaBr, NaCl, NaI and Na2SO4 and 2.0M Na2CO3.

Question 5

a) How many mL of 0.1 M CH3COONa must you add to 35.0 mL of 0.50 M CH3COOH to make a buffer of pH 4.7? [pKa of H3COONa is 4.75]

b) Use the Henderson-Hasselbalch equation to calculate how many mL of 0.1 M HCl must you add to 100 mL of 0.10 M Tris base to make a buffer of pH 8.8? [pka of Tris Base is 8.08]

c) What is the pH when 25.0 mL of 0.200 M of CH3COOH has been titrated with 35.0 mL of 0.100 M NaOH? Write out the balanced chemical equation.

d) *You need to produce a buffer solution that has a pH of 4.68. You already have solution that contains 15.0 mmol of CH3COOH. How many millimoles of CH3COONa should you add to this solution?

If a cell with a resting membrane potential of -70 mV is treated so that the resting membrane potential is at the equilibrium potential of K+, and then the permeability of the membrane for all ions is returned to normal: why WONT K+ move into the cell across the cell membrane until the resting membrane potential is restored but Na+ will?

The molecular structures of Cr(acac)₃ and Fe(acac)₃ are quite different from that of Mn(acac)₃. What are these structures? What is the true structure of the so-called manganic acetate? Please explain thoroughly.

The pH of a 0.016-M aqueous solution of p-toluidine (CH3C6H4NH2) is 8.60. Calculate Kb.

A 91.70 g sample of metal was heated in a boiling water bath at 99.4 °C. The hot metal was then placed in a calorimeter, with heat capacity 39 J/K containing 45.0 g of water. Analysis of the thermogram showed the initial temperature to be 21.1°C, the final temperature to be 42.3°C.

4.91 g of LiCl was dissolved in 50.0 mL of water in the same calorimeter as in problem (above)

1. Analysis of the thermogram showed the initial temperature to be 22.9C, the final temperature to be 49.2C.

Was the dissolution of the ionic solid exothermic or endothermic?

Calculate the mass of the water

Calculate delta H solution

Calculate delta H ( - above H with degrees) solution (assume constant pressure of 1 bar)

Please post work because I want to learn this material.. not just get answers. Thanks

A 91.70 g sample of metal was heated in a boiling water bath at 99.4 °C. The hot metal was then placed in a calorimeter, with heat capacity 39 J/K containing 45.0 g of water. Analysis of the thermogram showed the initial temperature to be 21.1°C, the final temperature to be 42.3°C.

Calculate Delta T water

Calculate Delta T metal

Calculate . CsPmetal

Calculate M (there's a - above the M.. don't know what that means) metal

What is the likely identity of the metal?

PLEASE post the material as I want to learn this material and not use chegg just to get answers.