Foundations In Chemistry 1 Flashcards
What is relative isotopic mass?
The mass of an isotope relative to 1/12th of the mass of an atom of Carbon-12.
What is an isotope?
Atoms of the same element with the same number of protons and different number of neutrons.
What is relative atomic mass?
The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of Carbon-12.
How to conduct mass spectrometry?
- Sample placed in spectrometer
- Sample vaporised and then ionised to form positive ions.
- Ions are accelerated- heavier ions move more slowly and are deflected less. The ions of the isotope become separated.
- Ions are detected as a ration of mass:charge (m/z)
- Each ion reaching the detector adds to the signal, so greater the signal greater the abundance.
- Mass to charge ratio = m/z = relative mass of an ion/ relative charge on ion.
What is relative molecular mass?
The mean average mass of the formula units relative to 1/12 of the mass of a Carbon-12 atom
What is ‘amount of substance’ ?
A means of counting atoms, its unit is the mole
What is Avogadro’s constant?
6.02 x 10^23
The number of atoms per mole of Carbon-12.
What is the mole?
The amount of any substance containing as many particles as there are Carbon atoms in 12 grams of Carbon-12 ( 6.02 x 10^23 particles)
What is the molar mass?
The mass per mol of a substance in gmol^-1
What is the empirical formula?
The simplest whole number ratio of atoms of each element in a compound.
How would you carry out an experiment to determine the water of crystallisation in hydrated salts?
Step 1- weigh an empty crucible
Step 2- add the hydrated salt into the weighed crucible, weigh the crucible and the hydrated salts
Step 3- using a pipe-clay triangle, support the crucible containing the hydrates salt on a tripod, heat the crucible and contents gently for about one minute. Then heat it strongly for a further three minutes.
Step 4- leave the crucible to cool. Then weigh the crucible and anhydrous salts.
What happens when blue crystals of hydrated copper (II) sulfate is heated?
Bonds holding the water within the crystal are broken and that water is driven off, leaving behind white anhydrous copper II sulfate
How to calculate number of moles
Mass/ molar mass
What is the empirical formula
Simplest whole number ratio of atoms of each element in a compound
What is molecular formula
Shows the number and type of atoms present of each element present in a compound
What is water of crystallisation
Water molecules that form an essential part of the crystalline structure of a compound.
They have a dot formula.
For example; SnCl4.8H2O
The dot formula shows how many water molecules are in that compound
Determination of the water of crystallisation of copper sulfate?
- Weigh an empty crucible and record weight
- Place about 4 spatulas of copper sulfate in the crucible and record weight.
- Support the crucible with the hydrates salt on a pipe-clay triangle, on a tripod. Heat the crucible with a Bunsen burner gently for a minute, then heat strongly for a further three.
- Leave the crucible to cool, then weigh the new mass of the crucible and now anhydrous salt
Unit for concentration
Mol dm -3
Number of moles calculation (conc)
Concentration (mol dm-3) X volume (dm3)
What is molar gas volume
Volume of space in dm3 taken up by one mole of gas volume is 24dm3 mol-1
What is avogadros law?
Equal volumes of gases at the same temperature and pressure contain each numbers of moles
What is a standard solution?
A solution with a known concentration
How to make standard solutions?
- Dissolve the salute in a small amount of distilled water.
- If dissolved in a beaker, transfer to volumetric flask with.
- Rinse the beaker with more distilled water, and add to the flask to minimise residue left behind.
- Fill the volumetric flask with distilled water tilt he meniscus reaches the etch mask on the flasks neck
What is the ideal gas equation?
PV= n R T
Pressure X volume = amount of gas molecules X ideal gas constant (8.31j mol-1) X temperature
What is the definition of an acid?
Chemicals that release hydrogen ions, referred to as protons, when dissolved in water
(proton donors)
What is a strong acid
An acid that completely dissociates into water to release H+ ions
What is a weak acid
An acid that only partially dissociates in water to release H+ ions
What is a base
A proton donor
Will react with protons released by acids
What is an alkali
Soluble bases that release OH- ions, when dissolved in water
What is water classed as and why?
‘Amphoteric’
It can be either an acid or a base, either donates or accepts protons
What was stated in Dalton’s atomic theory?
Atoms are tiny particles made of elements
Atoms cannot be divided
All the atoms in an element are the same
Atoms of one element are different to those in other elements
What did Thompson discovers about electrons
They have a negative charge
They can be deflected by magnet and electric field
They have very small mass
Explain the plum pudding model
Atoms are made up of negative electrons moving around in a sea of positive charge
What were Rutherford proposal after the gold leaf experiment?
Most of the mass and positive charge of the atom are in the nucleus
Electrons orbit the nucleus
Most of the atoms volume is the spare between the nucleus and the electrons
Overall positive and negative charges must balance
Explain the current model of the atom
Protons and neutrons are found in the nucleus
Electrons orbit in shells
Nucleus is tiny compared to the total volume of atom
Most of atoms mass is in the nucleus
Most of atom is empty space between the nucleus and the electrons
Define isotope
Atoms of the same element with different number of neutrons but same number of protons and electrons
Why do different isotopes in the same element react in the same way?
Neutrons have no impact on the chemical reactivity
Reactions involve electrons, isotopes have the same number of electrons in the same arrangement
What is the formula for dilution?
original concentration/ diluted concentration
What is a titre?
the volume of liquid used in a titration
What is the oxidation state of elements in their natural state?
0
What is the oxidation state of an ion?
The charge of that ion
What is a redox reaction?
transfer of electrons resulting in both oxidation and reduction of atoms
What does oxidation do to an oxidation state number?
increase it
What does reduction do to an oxidation state number?
decrease it
What is oxidation?
loss of electrons
What is reduction?
Gain of electrons
How can you test for carbonate ions?
Add dilute acid in to the sample
Collect the gas produced
Pass through lime water
CO2 released
How can you test for sulphate ions?
Add dilute hydrochloric acid and barium chloride to the sample
White precipitate of barium sulfate is produced
How can you test for a halide ion?
Dissolve sample in water
Add aqueous silver nitrate
Record the colour change
If difficult to distinguish the colour, add aqueous ammonia., first dilute ammonia then concentrated ammonia
Not solubility of precipitate
When testing for carbonate, sulfate and halide ions in which order should the tests be carried out and why?
1, carbonate test
2, sulfate test
3, halide test
Because barium ions forms insoluble precipitate of BaCO3 and silver ions form insoluble precipitate of Ag2SO4
How can you test for ammonium ions?
Add sodium hydroxide to the sample and warm it
Test the gas produced with red litmus paper
If ammonia is present, litmus paper turns blue
Ammonia has a pungent smell
How do you go from Celsius to kelvin?
Add 273 to the Celsius value
Formula for concentration
Mass / volume
Formula for moles
Both mass and concentrations
Mass / Mr
Conc X vol/ 1000
Formula for conc
(moles)
Moles X 1000/ volume
