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Advanced Higher Chemistry > U3-5 - Instrumental Analysis > Flashcards

U3-5 - Instrumental Analysis Flashcards

1
Q

Empirical formula

A

The simplest whole number ratio of the elements in a molecule.

(E.g. CH2 for any alkene)

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2
Q

If you are given % by mass of each element in the formula, how do you work out the empirical formula?

  1. Treat each % as __________.
  2. Divide each mass by the RAM of that element.
  3. Divide each number in the ratio by the smallest number in the ratio (to get whole numbers).
A

If you are given % by mass of each element in the formula, how do you work out the empirical formula?

  1. Treat each % as mass in grams.
  2. Divide each mass by the RAM of that element.
  3. Divide each number in the ratio by the smallest number in the ratio (to get whole numbers).
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3
Q

If you are given % by mass of each element in the formula, how do you work out the empirical formula?

  1. Treat each % as mass in grams.
  2. Divide each mass by ___________.
  3. Divide each number in the ratio by the smallest number in the ratio (to get whole numbers).
A

If you are given % by mass of each element in the formula, how do you work out the empirical formula?

  1. Treat each % as mass in grams.
  2. Divide each mass by the RAM of that element.
  3. Divide each number in the ratio by the smallest number in the ratio (to get whole numbers).
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4
Q

If you are given % by mass of each element in the formula, how do you work out the empirical formula?

  1. Treat each % as mass in grams.
  2. Divide each mass by the RAM of that element.
  3. Divide each number in the ratio by the _______________ (to get whole numbers).
A

If you are given % by mass of each element in the formula, how do you work out the empirical formula?

  1. Treat each % as mass in grams.
  2. Divide each mass by the RAM of that element.
  3. Divide each number in the ratio by the smallest number in the ratio (to get whole numbers).
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5
Q

If you are given masses of products, how do you work out the empirical formula?

  1. Mass of product _______________ (to work out the mass of each element)
  2. Divide each mass by the RAM of that element.
  3. Divide each number in the ratio by the smallest number in the ratio (to get whole numbers).
A

If you are given masses of products, how do you work out the empirical formula?

  1. Mass of product × mass of C/H/O etc. ÷ GFM of product (to work out the mass of each element)
  2. Divide each mass by the RAM of that element.
  3. Divide each number in the ratio by the smallest number in the ratio (to get whole numbers).
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6
Q

If you are given masses of products, how do you work out the empirical formula?

  1. Mass of product × mass of C/H/O etc. ÷ GFM of product (to work out the mass of each element)
  2. Divide each mass by______________.
  3. Divide each number in the ratio by the smallest number in the ratio (to get whole numbers).
A

If you are given masses of products, how do you work out the empirical formula?

  1. Mass of product × mass of C/H/O etc. ÷ GFM of product (to work out the mass of each element)
  2. Divide each mass by the RAM of that element.
  3. Divide each number in the ratio by the smallest number in the ratio (to get whole numbers).
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7
Q

If you are given masses of products, how do you work out the empirical formula?

  1. Mass of product × mass of C/H/O etc. ÷ GFM of product (to work out the mass of each element)
  2. Divide each mass by the RAM of that element.
  3. Divide each number in the ratio by____________________ (to get whole numbers).
A

If you are given masses of products, how do you work out the empirical formula?

  1. Mass of product × mass of C/H/O etc. ÷ GFM of product (to work out the mass of each element)
  2. Divide each mass by the RAM of that element.
  3. Divide each number in the ratio by the smallest number in the ratio (to get whole numbers).
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8
Q

If you have the empirical formula and the GFM, how do you find out the molecular formula?

  1. Calculate the mass of the __________.
  2. Divide GFM by empirical formula mass (to get how many times bigger the real formula is).
  3. Multiply empirical formula by this number.
A

If you have the empirical formula and the GFM, how do you find out the molecular formula?

  1. Calculate the mass of the empirical formula.
  2. Divide GFM by empirical formula mass (to get how many times bigger the real formula is).
  3. Multiply empirical formula by this number.
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9
Q

If you have the empirical formula and the GFM, how do you find out the molecular formula?

  1. Calculate the mass of the empirical formula.
  2. ____________ by empirical formula mass (to get how many times bigger the real formula is).
  3. Multiply empirical formula by this number.
A

If you have the empirical formula and the GFM, how do you find out the molecular formula?

  1. Calculate the mass of the empirical formula.
  2. Divide GFM by empirical formula mass (to get how many times bigger the real formula is).
  3. Multiply empirical formula by this number.
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10
Q

If you have the empirical formula and the GFM, how do you find out the molecular formula?

  1. Calculate the mass of the empirical formula.
  2. Divide GFM by empirical formula mass (to get how many times bigger the real formula is).
  3. _________ empirical formula by this number.
A

If you have the empirical formula and the GFM, how do you find out the molecular formula?

  1. Calculate the mass of the empirical formula.
  2. Divide GFM by empirical formula mass (to get how many times bigger the real formula is).
  3. Multiply empirical formula by this number.
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11
Q

Parent ion

A

The molecule being analysed (in mass spec) with one electron removed (so a 1+ charge).

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12
Q

How do you get the GFM from mass spec data?

A

m/z of the parent ion is equal to GFM

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13
Q

Identify the parent ion peak

A
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14
Q

Base peak

A

The most abundant peak (in a mass spectrum)

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15
Q

Identify the base peak

A
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16
Q

(Mass spec) fragment with m/z of 15

A

[CH3]+

17
Q

(Mass spec) fragment with m/z of 17

A

[OH]+

18
Q

(Mass spec) fragment with m/z of 28

A

[C=O]+

19
Q

(Mass spec) fragment with m/z of 29

A

[C2H<span>5</span>]+

20
Q

(Mass spec) fragment with m/z of 77

A

[C6H<span>5</span>]+

21
Q

Units used to measure IR absorbance

A

Wavenumbers (cm–1)

22
Q

When IR radiation is absorbed by organic compounds, bonds within the molecule _______.

A

vibrate (stretch and bend)

23
Q

How can different functional groups be identified using IR?

A

Different functional groups absorb IR at different wavenumbers

24
Q

The number of peaks in a low resolution proton NMR spectrum is equal to _____.

A

the number of different chemical environments (for H atoms) in the molecule

25
Q

In NMR spectra, peaks corresponding to different chemical environments have different ____.

A

chemical shifts

26
Q

What information do integration curves provide?

A

Ratio of H atoms in each chemical environment (equal to height ratio of integration curves).

27
Q

In high res NMR, peaks will split into multiplets. Why is this?

A

Protons on adjacent carbons interact with each other (and split the signal coming from their neighbour).

28
Q

How can you predict the no. of peaks in a multiplet? (NMR)

A

Using the n+1 rule, where n = no. of protons on neighbouring C atoms.

(3H on adjacent carbons ⇒ 3+1=4 peaks)

29
Q

How many peaks will be in the multiplet for the H circled? (NMR)

A

4 (3H on adajcent carbons)

Advanced Higher Chemistry (15 decks)

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