Putting the Solvent Into a Calculation · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Adding the solvent to your calculation

Science · Chemistry · ages 23-24
Name ______________________   Date ____________

  1. Your solute forms a hydrogen bond to the solvent. What must you add to the calculation?

    • The bonded partners as real molecules
    • A larger vacuum box
    • A higher temperature setting

  2. What does a continuum model put in place of the liquid?

    • One real water molecule
    • A vacuum with nothing in it
    • A smooth polarisable medium

  3. A continuum model can show individual hydrogen bonds to the solute.

    Circle one:   True   False

  4. A solute holds hydrogen bonds to a few first shell partners. Which molecules do you include explicitly?

    • Only those bonded partners, with the medium around them
    • Every molecule in the beaker
    • None, since the medium covers such bonds

  5. A computed solvation energy for an ion misses the measured value by a wide margin. What best accounts for the gap?

    • The dielectric constant simply needs a bigger value
    • The shell is incomplete or the cavity settings are off
    • A vacuum result is already enough for an ion

  6. A polar solvent lowers a barrier when the transition state holds more separated charge than the reactants.

    Circle one:   True   False

  7. A computed ion solvation energy is minus 300 kilojoules per mole, and the measured value is minus 340. By how many kilojoules per mole do the two differ? Type the number.

    Answer: ______________

  8. Two ions react, and the gas phase barrier disagrees badly with experiment. What is missing and how do you fix it?

    • The timing of the probe pulse
    • The solvent: add the medium, plus real molecules where bonds work
    • A longer run with the same vacuum forces
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Adding the solvent to your calculation W1-mt_3SCFfcvoei-s1

  1. The bonded partners as real molecules · Specific bonds need real molecules, with the medium kept around them.
  2. A smooth polarisable medium · The continuum is a smooth medium set by the dielectric constant.
  3. False · No real molecules sit inside it, so specific bonds are absent.
  4. Only those bonded partners, with the medium around them · You include the molecules that do specific work and let the medium cover the rest.
  5. The shell is incomplete or the cavity settings are off · A wide ion gap means missing shell structure or bad cavity settings.
  6. True · Tracking charge tells you the direction the barrier moves.
  7. 40 · Take the gap between the values: 340 minus 300 is 40.
  8. The solvent: add the medium, plus real molecules where bonds work · Ions in vacuum miss solvation, so the medium and bonded partners must enter.
Worksheet · LightMySky