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~AS Chemistry Edxl 1

AS Edexcel Chemistry - Unit 1

QuestionAnswer
Name the 3 particles in an atom Protons, neutrons and electrons.
What are the relative charges of: A) protons B) neutrons C) electrons ? A) +1 B) 0 C) -1
What are the relative masses of: A) protons B) neutrons C) electrons ? A) 1 B) 1 C) 1/1800
What does the mass number tell you? The total number of protons and electrons in the nucleus.
What does the atomic number tell you? The number of protons in the nucleus. From this you can also work out what element it is as all atoms of the same element have the same number of protons.
How do you work out the number of neutrons in an atom? Mass number minus atomic number.
What is an ion? Negative ions have more electrons than protons, Positive ions have more protons than electrons.
What is an isotope? Isotopes are atoms of the same element with different numbers of neutrons.
ΔH is positive for what type of reaction? (exothermic or endothermic) Endothermic. It absorbs energy, making it feel cold.
ΔH is negative for what type of reaction? (exothermic or endothermic) Exothermic. It gives out energy, making it feel hot.
In an energy profile diagram, what type of reaction would be shown when the enthalpy of products is less than enthalpy of reactants. This would be an exothermic reaction as the overall ΔH would be negative.
In an energy profile diagram, what type of reaction would be shown when the enthalpy of products is more than enthalpy of reactants. This would be an endothermic reaction as the overall ΔH would be positive.
What are the standard enthalpy conditions? 298k and 100kPa
What is the standard enthalpy change of reaction? The enthalpy change when the reaction occurs in the molar quantities shown in the chemical equation.
What is the standard enthalpy change of formation? The enthalpy change when 1 mole of a compound is formed from its elements in their standard states.
What is the standard enthalpy change of atomisation? The enthalpy change when 1 mole of gaseous atoms is formed form an element in its standard state.
What is the standard enthalpy change of combustion? The enthalpy change when 1 mole of a substance is burned completely in oxygen
What is the standard enthalpy change of neutralization? The enthalpy change when 1 mole of water is formed by the neutralization of positive hydrogen ions by negative hydroxide ions.
What is Calorimetry and what is it used for? Burning a flammable liquid under some water and measuring the temperature change of the water. This can be used to calculate the enthalpy of combustion however it is not always accurate as some heat is always lost to surroundings.
What is the formula for enthalpy change? ΔH = (M x C x ΔT)/molar mass (M = mass of water used, C = specific heat capacity and ΔT = change in temperature of water)
Give 4 reasons why the experimental enthalpy value may be lower than the theoretical. - some heat absorbed by container, not water itself. - some heat lost into surroundings. - the combustion may be incomplete (giving out less energy) - some of the flammable liquid may have evaporated
State Hess' Law. the enthalpy change for two different routes from the same reactants to the same products-will be equal.
What are the 5 steps in a mass spectrometer? Vaporisation- Heat the sample. Ionisation- Bombard with electrons to make +tive ions. Acceleration- accelerate using electric field. Deflection- only atoms with the right mass will be sent to detector. Detection- ions that reach it are detecte
What is the equation to find relative abundance of an isotope using a mass spectrum? sum of each mass times it's relative abundance, divided by the sum of all relative abundances.
Name 4 uses for Mass Spectrometry. Carbon dating, Identifiying compounds in the parmaeceutical industry, drugs testing, mars probes
What are the shapes for the S P and D orbials? S- circle P-oval D- lopsided oval
Express Calcium (20) using S, P and D notation. 1S2, 2S2, 2P6, 3S2, 3P6, 4S2
What is ionisation? The removal of one or more electrons.
Define first ionisation energy. The energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form one mole of positive gaseous ions.
Name and explain 3 factors which affect 1st ionisation energy. Nuclear charge - more protons makes higher ionisation energy. Radius - larger radius makes lower ionisation energy. Shielding - higher number of electrons shielding lowers ionisation energy.
Describe the trend in 1st ionisation energy down a group. Decreases due to increasing radius.
Describe the trend in 1st ionisation energy across a period. generally increase due to increasing charge from the nucleus.
Explain how sucessive ionisation energies can show shell structure. Big jumps between ionisation energies show the loss of a shell. the number of ionisations before the big jump shows the group it is in.
PAGES 32-36 STILL NEED TO BE DONE!!! DO THEM SOOOOON!!!
What is the name and charge of and NO3 ion? Nitrate -1
What is the name and charge of and CO3 ion? Carbonate -2
What is the name and charge of and SO4 ion? Sulfate -2
What is the name and charge of and NH4 ion? Ammonium +1
What is an ionic bond? A bond between a Metal and a Non-Metal.
What is a covalent bond? A bond between two Non-Metals.
What is an alloy? Two or more mettals bonded together.
What is the equation for atom economy%? (Mass of useful products/mass of reactants)x100
what charge ions do A) group 1 B) group 2 C) group 6 D) group 7 atoms make? A) 1+ B) 2+ C) 2- D) 1-
Name and explain some physical properties given due to ionic bonding. High melting points due to strong attractions. Soluble which means that the ions are charged. They only conduct electricity when molten because the ions can move around freely.
As you gown a group, the ionic radius... (increases/decreases)? Increases because there are more electron shells.
Describe one experiment that can give evidence for the existence for ions. The Migration Of Ions On Wet Filter Paper. Place a drop of copper(II) chromate(IV) solution on some wet filter paper, attatch electrodes to either end; the negative chromate(VI)ions will move to the anode, positive Copper(II)ions will move to the cathode
When drawing a born-haber cycle, what indicates the beginning of the cycle? Both elements must be in their standard states.
How can Born-Haber cycles be used to show why some compounds don't exist? Eg. born haver cycle gives negative enthalpy of formation of NaCl. as this should be a positive enthalpy, the compound does not exist.
How do you tell from enthalpies of formation, which compound is most stable? The one that has the lowest overall ΔH value.
How do you calculate the charge density of a cation? Charge density = charge / volume
How can you tell how ionic a lattice is, using different lattice energy values? If the experimental born-haber value is similar to the Theoretical lattice energy, then it is 'purely ionic. The further apart they are(%) the more covalent character they have as they are more polarised.
What characteristics make a cation very polarising? Small cations with a large charge. (e.g ones with a high charge density)
What type of anion is the most easily polarised? Large anions which have less pull on their outer electrons.
What type of bond holds molecules together? Covalent
How is a sigma bond formed? and what shape is it? When 2 S-orbitals overlap. It is sort of peanut shaped, an over that is smaller in the middle and larger at both ends.
How is a pi bond formed? and what shape is it? When 2 P-orbitals overlap. It forms 2 moon shapes on either side of the nuclei, where one side of each P bond joins with the corresponding side of the other p bond.
What is Dative covalent bonding? When both electrons in a bond come from one atom.
These are notes made from CGP book up to page 46. PAGE 46
Created by: UoBathPhysics