Unit 3- Area of Study 1: Chemical Analysis Flashcards
Define relative atomic mass.
The weighted mean of the relative isotopic masses of an element on the scale where carbon-12 is 12 exactly. (Symbol:Ar)
Define relative molecular mass.
The relative mass of a molecule on the scale where carbon-12 is 12 exactly. It is equal to the sum of the relative atomic masses of the atoms in the molecule. (Symbol: Mr)
Define mole.
The amount of substance that contains the same number if fundamental particles as there are atoms in 12g of carbon-12. (Symbol:n)
Define Avogadro’s number.
Number of particles in a mole; 6.02 X 10^23 (Symbol: NA)
Define molar mass.
The mass of one mole of a substance. It is equal to the relative mass of the substance expressed in grams. (Symbol: M)
Define precipitate.
A solid formed during a reaction in which two or more solutions are mixed.
What is gravimetric analysis?
A quantitative analytical technique which is based on the mass of a substance and involves precipitation and weighing.
What is an ionic equation?
An equation that contains only the ions that are involved in the reaction.
What us the instrument used in gravimetric analysis?
An analytical balance scale.
What are the advantages of using an analytical balance scale as opposed to a regular scale?
- There is no contamination of the sample.
- Environmental factors don’t affect the mass of sample.
- An accurate measurement up to 4 decimal places is given.
In what situations is gravimetric analysis used?
1) Measuring water content in the sample.
2) Determining the composition in a mixture.
3) Determining the chemical formula of a compound.
What are the steps involved in measuring the water content in a sample?
1) Weigh the sample (M1 g-initial mass)
2) Heat the sample in an oven at 110 deg cel. *Never measure a sample when it is hot because as the temp is increased, pressure is increased and this affects the mass to 4 d.p. *
3) Allow sample to cool in a dessicator
4) Reweigh the sample (M2 g- final mas)
5) Repeat steps 2-4 until final mass is constant.
Define empirical formula.
The simplest whole number mole ratio of elements in one mole of a compound.
Define molecular formula.
The exact whole number mole ratio of elements in one mole of a compound.
List the various analytical techniques used for chemical analysis.
- Gravimetric analysis
- Volumetric Analysis
- Chromatographic analysis
- Spectroscopic tecnhique
- Mass spectrometry