Free Response-Answer all questions completely showing all necessary work require
ID: 947619 • Letter: F
Question
Free Response-Answer all questions completely showing all necessary work required. Be sure to include the correct sig figs and units in any numerical answer. Circle answers to aid in finding final answer. Calculate the mass of oxygen (in mg) dissolved in a 5.00 L bucket of water exposed to a pressure of 1.13 atm of air. Assume the mole fraction of oxygen in air to be 0.21 and the Henry's Law Constant for oxygen in water at this temperature to be 1.3 x 10^3 M/atm. MH_3 that must be dissolved in 475 g of What .5 the mass (in grams) of NH, that must methanol to make a 0.250 m solution?Explanation / Answer
21) Enthalpy change of solution dH(sol) = dH(solute) + dH(hydration energy)
dH(solute) = dH(solution) - dH(hydration energy)
dH(solute) = 19.9KJ/mol - (-670KJ/mol) = 689.9KJ/mol
22) C = k*P
P = P°*X
C = P°*X*k = 1.13atm * 0.21 * 1.3*10^-3M/atm = 3.085*10^-4M
3.085*10^-4M * 5L = 1.54*10^-3mol = 1.54mmol
1.54*MM*(molar mass of O2) = 1.54mmol * 32mg/mmol = 49.4mg
Therefore the mass of oxygen dissolved in 5.0 L buccket = 49.4mg
23) molality = moles of solute / kg solvent
No.of moles of NH3 may be calculated as
0.250 m = mol NH3 / 0.475 kg
mol NH3 = 0.11875
calculate the weight of solute from moles
(0.11875 mol) ( 17.04 g / mol) = 2.0235 g
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