The 1h nmr signal for bromoform (chbr3) appears at 2065 hz when recorded on a 300−mhz nmr spectrometer. if the spectrum was recorded on a 200−mhz instrument, what would be the chemical shift of the chbr3 proton? enter your answer in the provided box.

The chemical shift (δ) for CHBr₃ proton = 6.88 ppm

Explanation:

In NMR spectroscopy, Chemical shift (δ) is expressed in parts per million (ppm) and is given by the equation:

                    ....equation (1)

Given: Observed frequency: ν₁ = 2065 Hz,

Spectrometer frequency: ν'₁ = 300 MHz, ν'₂ = 200 MHz

To calculate the chemical shift (δ) for the given CHBr₃ proton, we use the equation (1)

Since in NMR spectroscopy, chemical shift is a field independent scaling. Thus the value of the chemical shift of a given proton, such as CHBr₃ proton, is independent of the magnetic field strength of the spectrometer.

So the value of chemical shift of a given proton remains same when measured with a 300 MHz and 200 MHz NMR spectrometer.

Therefore, the chemical shift (δ) for CHBr₃ proton = 6.88 ppm

first, consult an activity series chart to determine if al is more reactive than fe. it is, so it will replace the fe. now, one can continue with the problem.

next, make sure you have a correctly balanced equation.

3feo + 2al ==> 3fe + al2o3

now, determine which reactant (feo or al) is in limiting supply.

moles feo present = 125 g x 1 mole/71.8 g = 1.74 moles

moles al present = 25.0 g x 1 mole/26.98 g = 0.927 moles

since from the balanced equation, it take 3 mol feo for every 2 mol al, al will be limiting.

you can determine this simply by dividing moles of each by their coefficient in the balanced equation. for example: 1.74/3 = 0.58 and 0.927/2 = 0.464. al is less, so it is limiting.

finally, using the stoichiometry in the balanced eq. determine mass of fe that can be produced from 0.927 moles of al.

0.927 moles al x 3 moles fe/2 moles al x 55.8 g/mole = 77.6 g