How many moles of urea (60. g/mol) must be dissolved in 66.6g of water to give a 2.4 m solution? a. 1.4 × 102 mol
b. 2.4 mol
c. 0.0024 mol
d. 0.15 mol
e. 9.0 × 102 mol

d. 0.15 mol

Explanation:

Step 1: Given data

Mass of water (solvent): 66.6 gMolality (m): 2.4 mMoles of urea (solute): ?

Step 2: Convert the mass of the solvent to kilograms

We will use the relationship 1 kg = 1,000 g.

66.6 g × (1 kg/1,000 g) = 0.0666 kg

Step 3: Calculate the moles of solute

The molality is equal to the moles of solute divided by the kilograms of solvent.

m = moles of solute / kilograms of solvent

moles of solute = m × kilograms of solvent

moles of solute = 2.4 mol/kg × 0.0666 kg

moles of solute = 0.15 mol

Any photo? or something

  remember that hf is only the energy of one photon. not two. not three. one.  1) 5.12 * 10^3 photons  find the energy of one photon, then determine how many photons are needed to reach the sensitivity.  e = hf  = (6.626 * 10^-34 js)(5.95 * 10^19 hz)  = 3.94247 * 10^-14 j per photon  (2.02 * 10^-10 j) / (3.94247 * 10^-14 j/photon) = 5123.69149 photons  round to three sig figs.  2) 5.77 * 10^-17 j  energy of pulse = energy per photon * number of photons  = hfn  = (6.626 * 10^-34 js)(1.66 * 10^13 hz)(5250)  = 5.774559 * 10^-17 j  round to three sig figs.  3) 4.07 * 10^8 kj/mol  10^12 pm = 1 m  c = fλ  f = c/λ  e = hf  = hc/λ  = [(6.626 * 10^-34 js)(3.00 * 10^8 m/s) / (2.94 * 10^-12 m)](1 kj/1000 j)(6.02 * 10^23 photons/mol)  = 40702571.4 kj/mol  round to three sig figs.  4) 9.94 * 10^-1 m  e = hc/λ  λ = hc / e  = (6.626 * 10^-34 js)(3.00 * 10^8 m/s) / (2.00 * 10^-25 j)  = 0.9939 m  round to three sig figs.  5) 9.06 * 10^3 photons  energy of pulse = energy per photon * number of photons  number of photons = energy of pulse / energy per photon  = energy of pulse / (hf)  = (3.87 * 10^-13 j) / [(6.626 * 10^-34 js)(6.45 * 10^16 hz)]  = 9055.23695 photons  round to three sig figs.  6) 2.78 * 10^-15 j  this is problem 1, except in reverse.  sensitivity = minumum number of photons * energy per photon  = (5930)(6.626 * 10^-34 js)(7.077 * 10^14 hz)  = 2.78070758 × 10^-15 j  round to three sig figs.