# Chemistry CH1 - THINGS I KEEP FORGETTING

• Created by: Tasha.L
• Created on: 07-05-16 18:36
Why is the ionisation energy of Sulphur lower than that of Phosphorus?
Sulphur's outer electrons are in a paired 3p orbital: the repulsion between pairs of electrons makes it easier for an electron to be lost, so less energy is required.
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What is the relationship between frequency and energy?
E = hf, where h is Planck's constant.
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What is the relationship between frequency and wavelength?
f = c/wavelength, where c is the speed of light.
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Why do the lines of an emission spectrum get closer together at the high frequency end of the spectrum?
The energy levels furthest from the nucleus get closer together as the energy difference decreases, and the transitions are of the highest frequency.
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Why does the relative molecular mass not have units?
It is a relative quantity.
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Define relative atomic mass.
The weighted average mass of all the atoms in a normal isotopic sample of an element, on the scale where one atom of carbon-12 has a mass of 12g exactly.
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Define relative isotopic mass.
The average mass of an atom in a particular isotopic sample of an element, on a scale where one atom of carbon-12 has a mass of 12g exactly.
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Define relative formula mass.
The average mass of a molecule, on a scale where one atom of carbon-12 has a mass of 12g exactly.
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Define relative molecular mass.
The ratio of the average mass of one molecule of an element or compound, on the scale where one atom of carbon-12 has a mass of 12g exactly.
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Define the mole.
The number of particles equal to the number of atoms in 12g of carbon 12.
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Why do several lines occur on a mass spectrum?
When a vaporised sample is ionised, it forms positively charged ions, called the molecular ions. These are energetically unstable and so split into various fragments, hence why numerous lines occur.
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6.022 x 10^23
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State the ideal gas equation.
pV = nRT
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How do you convert temperature from Celsius to Kelvin?
Celsius + 273 = Kelvin, as O Celsius = 273 Kelvin.
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Define atom economy.
The percentage by mass of all the reactants in the desired product.
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State the atom economy equation.
(Mr of desired product)/(Mr of all reactants) x 100
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State the percentage yield equation.
(Mass of product obtained)/(Mass of theoretical product) x 100
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State the percentage error equation.
(Error on equipment)/(value obtained) x 100
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Define electronegativity.
The electron attracting power of an atom within a covalent bond.
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How many carbon atoms are covalently bonded to each carbon atom in a diamond?
Four.
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What are between the carbon layers in graphite?
Delocalised electrons!
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Define a metal.
A lattice of positively charged metal ions held together by their attraction to a sea of delocalised electrons
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Define a redox reaction.
When reduction and oxidation reactions occur simultaneously.
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Why do group 4 elements have the highest melting point?
They form giant covalent structures.
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How do you test for sulphate ions?
1. Add HCl to remove impurities, such as carbonates. 2. Add barium chloride. If a white ppt forms, sulphate ions are present.
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What is the thermal stability trend of the group 2 metals?
Increases down the group.
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What is the difference between the flame colour of lithium, strontium and calcium?
Lithium = red. Strontium = Crimson. Calcium = BRICK red.
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What is a reversible reaction?
When the reactants are turned into products at the same time as products are turned into reactants.
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State the equation to work out the pH of a solution.
pH = -log[H+]
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State the equation to work out the [H+] of a solution.
[H+] = 10^-pH
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Why are rough titrations conducted?
To get a rough idea of where the end point should be.
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Give an example of a primary standard.
Potassium Hydrogen Phthalate - this can react with both acids and bases.
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Spell the last word in the previous question.
P-H-T-H-A-L-A-T-E
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What is standardisation?
The process of determining the exact concentration of a solution.
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What is a primary standard?
A reagent which can be easily weighed, and is so pure that its mass is truly representative of its moles.
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What happens in a back titration?
An excess of one mixture is reacted with another mixture of an unknown concentration. The excess solution that remains is then titrated with a base/acid to determine the number of moles. THEN WORK BACKWARDS.
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Why are metals malleable?
When a force is applied the layer of metal ions slide over each other to form a new shape.
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What is a covalent bond?
The electrostatic attraction between positively charged nuclei and a shared pair of electrons.
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What deflects the ions in a mass spectrometer?
Magnetic field, produced by the electromagnet.
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What accelerates the particles in a mass spectrometer?
A negatively charged accelerating plate.
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State the equation of the reaction of magnesium with steam.
Mg(s) + H2O(g) --> MgO(s) + H2
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Is Magnesium Hydroxide insoluble or soluble?
Insoluble - it forms a white precipitate.
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Is Barium Sulphate insoluble or soluble?
Insoluble - it forms a white precipitate.
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Will Chlorine displace iodine in Potassium Iodide?
Yes - chlorine is a better OXIDISING AGENT than iodine (not: more reactive).
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What happens in the nucleus of an atom when a beta particle forms?
A neutron turns into a proton, and an electron is emitted.
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How are electrons arranged within atoms?
Electrons are found in fixed energy levels. Electrons occupy orbitals within these energy levels. The first energy level has s orbitals, whilst the second has both s and p orbitals.
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How are electrons arranged within atoms?
each with opposite spin. Orbitals of the same type of grouped together, forming sub-shells.
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Complete the definition for relative atomic mass: the weighted average mass of one atom of an element relative to...
1/12th the mass of one atom of carbon-12.
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Describe the nature of a pure covalent bond.
High electron density evenly shared between two nuclei.
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Describe the nature of an intermediate bond.
High electron density shared between two atoms, but higher near one atom.
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Describe the nature of a pure ionic bond.
High electron density centered around atoms.
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What is the bond angle of a molecule with 3 bond pairs and 2 lone pairs?
86 degrees (trigonal planar)
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What are the problems of chlorine in water treatment?
a. People have no choice when added to a public water supply. b. High dosages can be lethal.
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What are the problems of using fluorine for water treatment?
a. Discolours teeth. b. Can increase chances of bone cancer. c. When added to a public water supply people have no choice.
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What are the benefits of using fluorine in water and toothpaste?
a. Strengthens teeth and bones.
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## Other cards in this set

### Card 2

#### Front

What is the relationship between frequency and energy?

#### Back

E = hf, where h is Planck's constant.

### Card 3

#### Front

What is the relationship between frequency and wavelength?

#### Back ### Card 4

#### Front

Why do the lines of an emission spectrum get closer together at the high frequency end of the spectrum?

#### Back ### Card 5

#### Front

Why does the relative molecular mass not have units?

#### Back 