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Chemistry AS Paper 1
UWU IM GOING TOO SUCK OUT UR SMEGMA
| Question | Answer |
|---|---|
| Define atomic number | Number of protons in atoms nucleus |
| Define mass number | Number of protons and neutrons in atoms nuclues |
| Define isotopes | Constant for the amount of atoms in a substance. Also the number of atoms in one mole of C-12 |
| Define empirical formula | The simplest ratio of atoms of each element in a single compound |
| Define relative atomic mass | Average mass of atoms compared to C-12 |
| Define relative molecular mass | Ratio of average mass of one molecule of an molecule compared to the mass of 1/12 of C-12 |
| Define first ionization energy | energy required to remove 1 electron from an atom in its gaseous form to make a 1+ ion |
| Define second ionization energy | energy required to remove 1 electron from an 1+ ion in its gaseous form to make a 2+ ion |
| Define dative covalent bonding also known as coordinate bonding | Where the shared electron in the covalent bond comes from a single atom |
| Define electronegativity | How strongly an atom attracts pair of electrons in a bond |
| Define polar bond | One part of a molecule is slightly more negative or positive then the rest |
| Define exothermic | A reaction that gives out energy to its surroundings |
| Define endothermic | A reaction that takes in energy from its surroundings |
| Define enthalpy change | The energy change in a reaction taking place under a constant pressure |
| Define specific heat capacity | amount of energy required go raise the temperature of one gram of a substance by 1c (equal to 1k) |
| Define Hess law | The total enthalpy change between products and reactants are the same |
| Define standard enthalpy of formation | The change of enthalpy during the formation of 1 mole of the compound by its individual elements |
| Define standard enthalpy of combustion | The change of enthalpy during the complete combustion in an excess of oxygen in standard state and conditions. |
| Define bond enthalpy | energy required to break a particular covalent bond in one mole of a molecule in a gaseous state |
| What is Dative covalent bonding? | When both electrons in a bond come from one atom. |
| 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 characteristics make a cation very polarising? | Small cations with a large charge. (e.g ones with a high charge density) |
| 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. |
| ΔH is positive for what type of reaction? (exothermic or endothermic) | Endothermic. It absorbs energy, making it feel cold. |
| What are the standard enthalpy conditions? | 298k and 100kPa |
| 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) |
| 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 |
| Express the order of electron orbitals up till 5s | 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2 |
| Describe the trend in 1st ionisation energy down a group. | Decreases due to increasing radius. |
| 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 across a period. | generally increase due to increasing charge from the nucleus. |
| What is the equation for atom economy%? | (Mass of useful products/mass of reactants)x100 |
| 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 |
| 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. |
| 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. |
| Define Avogadro's number | Constant for the amount of atoms in a substance. Also the number of atoms in one mole of C-12 |
| moles, mass, mr equation with units | moles (mol) = Mr (g/mol) / mass (g) |
| concentration, volume and amount of substance (moles) equation | Concentration (mol dm-3) = moles (mol) / volume (dm3) |
| Ideal gas equation | PV= nRT |
| Mass of water per ml | 1 gram |
| 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. |
| 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. |
| Symbols for covalent bond with 2 electrons (single bond) and 4 electrons (double bond) | Single covalent bond is a line connecting the elements and double pair is two lines. |
| Symbol for a coordinate/dative bond | Arrow to the element not providing an electron from the element that is providing two electrons. |
| define metallic bond | the attraction of valence electrons for the positive kernels of metallic atoms, a mobile sea of electrons |
| dipole-dipole forces | force of attraction |
| hydrogen bond | the (electrostatic / intermolecular) attraction between a partially positively charged hydrogen atom in one molecule for a partially negatively charged nitrogen, oxygen,or fluorine atom in another molecule. |
| valence electrons | electrons in the outer most energy level of an atom |
| Describe the structure of ionic compounds | Giant ionic lattice of positive and negative ions held together by electrostatic forces |
| Explain the melting point of ionic compounds | High melting point because strong electrostatic forces within ionic lattice which require a great deal of energy to break |
| Explain the electrical conductivity of ionic compounds | Conduct when molten or dissolved because ions can move but do not conduct as a solid because ions held in fixed position in lattice |
| Describe the structure of graphite | Layers of carbon atoms arranged in hexagonal pattern with weak bonds and delocalised electrons between layers |
| Explain why graphite conducts electricity | Delocalised electrons are free to move and carry charge |
| What is the bond angle in a linear molecule? | 180° |
| What is the bond angle in a trigonal planer molecule? | 120° |
| What is the bond angle in a tetrahedral molecule ? | 109° |
| What shape molecule has 5 bonding pairs (eg. PCl5) and what are the bond angles | Trigonal bipyramidal, 90 degrees and 120 degrees |
| How do lone pairs affect bond angles | Reduce bonding pair bond angles (by approx. 2 degrees per lone pair) as they repel more than bonding pairs |
| What is the shape and bond angle in water. Why | Bent, 104.5 degree, 4 pairs of electrons including 2 lone pairs |
| What causes molecule to be polar (2 requirements) | significant differences in electronegativity and asymmetrical shape |
| Name the 3 types of intermolecular force in order from weakest to strongest | Van der Waals, dipole-dipole and hydrogen bonding |
| Which type of intermolecular force exists between diatomic molecules | Van der waals only |
| when does dipole dipole occur | when the partial charges formed within one molecule are attracted to an opposite partial charge in a nearby molecule |
| Describe the structure of ice | Regular lattice structure of water molecules held together by hydrogen bonding. Less dense than water |
| Describe the strucutre of metals | Giant metallic lattice of positive metal ions surrounded by delocalised electrons |
| Explain why metals have high melting points | The delocalised electrons are strongly attracted to the positive metal ions (strong metallic bonds) which requires a lot of energy to overcome |
| Describe the bonding in diamond | Each carbon is bonded to 4 other carbons in a tetrahedral shape |
| Describe the structure of iodine | Molecular lattice of I2 molecules held tougher by Van der Waals forces |
| Explain why Mg has a higher melting point than Na | Doubly charged metal ion |
| Which would you expect to have a higher melting point, NaCl or MgO and why | MgO because ions are double the charge of NaCl so stronger electrostatic forces |
| See slides for bond angles and shappes upto 6 electrons | UWU MEOW DADDY BOJO IS A BHADDIE WITH A PPHATTY!!!! NEEEKKKOOOO NEEEKOOO NEEEE |
| Explain why some molecules with polar bonds do not have permanent dipole | Although the bonds are polar, if the molecule is symmetrical then the dipoles "cancel" eachother and there is no overall dipole on the molecule. |
| What is a London Force (sometimes called an induced dipole-induced dipole attraction.)? | London forces are the attractive forces that cause nonpolar substances to condense to liquids and to freeze into solids when the temperature is lowered sufficiently. It is the weakest intermolecular force |
| London Dispersion Forces/London Dispersion Forces | intermolecular bonds btwn nonpolar molecules. cold temps to break |
| Calorie (cal) | Unit of energy defined as the amount of energy required to raise the temperature of one gram of water by one Celsius degree. Equal to 4.184 Joules |
| Boyle's Law | Volume and pressure are inversely proportional |
| Charles's Law | Volume and temperature are directly proportional |
| Gay-Lussac's Law | Pressure and temperature are directly proportional |
| Ideal Gas Law | Law that combines Boyle's, Charles's, Avogadro's, and Gay Lussac's Law into one comprehensive equation: PV = nRT. P is pressure, V is volume, T is temperature, R is a constant, and n is moles of gas |
| Avogadro's Law | Volume and amount of substance (in moles) are directly proportional |
| Ideal Gas | Hypothetical gas that perfectly follows the ideal gas law under all conditions |
| molar enthalpy change formula | Molar enthalpy = DH/n. n = number of moles of reactant. So we convert the carefully measured mass in to moles by dividing by molar mass. C = concentration in “M” = moles/L. |
| Define activation energy (collision theory) | minimum energy with which molecules must be moving in order for a collision to result in a chemical reaction is known as the activation energy. |
| Why do most collisions not lead to a reaction? | most collisions have energy less than the activation energy of the reaction and thus the reaction cannot proceed. Additionally the steric factor effects the rate of reaction. |
| le chatelier's principle | The position of the equilibrium of a system changes to minimise the effect of any imposed change in conditions |
| Boltzmann Distribution | molecular energies in a gas at constant temperature. Most gas molecules have energies within a comparatively narrow range. The curve will only meet the energy axis at infinity energy. |
| Homogenous Mixture | Mixture in which the composition is the same throughout |
| Kc equation? | Products concentration/reactants concentration ... All coefficients are made into indices |
| Oxidation | Loss of electrons, producing a more positive charge |
| Reduction | Gain of electrons, producing a more negative charge |
| Oxidation Number | Positive or negative whole number that represents the "charge" an atom in a compound would have if all shared electrons were assigned to the atom with a greater attraction for those electrons |
| Oxidizing Agent | Substance that causes the oxidation of another substance in reaction; this is reduced in a redox reaction |
| Reducing Agent | Substance that causes the reduction of another substance in reaction; this is oxidized in reaction |
| Reduction half equation? | Oxidant + e- --> Product |
| Oxidation half equation? | Reductant --> Product + e- |
| Trend in atomic radius across a period? | he atomic radius of the elements decreases because the number of protons increases so the nuclear charge increases. |
| Why does atomic radius increase down group 2? | the greater the atomic number the more electrons there are; these go into shells increasingly further from the nucleus |
| Why does melting point decrease down group 2? | each atom contributes two electrons to the delocalised cloud, metallic bonding gets weaker due to increased size of ion, Larger ions mean that the electron cloud doesn’t bind them as strongly |
| Why does first ionisation energy decrease down group 2? | Why is the second ionisation energy of Magnesium higher than the first ionisation energy? |
| What is the trend in solubility of the Group 2 Hydroxides? | They get more soluble down the group. |
| Why do the group 2 metals get more reactive as you go down the group? | Reactivity of metals is related to their ionisation energy. The ionisation energies of metals decreases down the group due to increased shielding and increased distance from the nucleus to the outer shell |
| What is the trend in solubility of the Group 2 Sulphates? | They get less soluble down the group. |
| Describe the chemical test for sulfate ions | Use barium chloride in the presence of dilute hydrochloric acid. This will produce a white precipitate if sulfate ions are present. |
| Why does the boiling point of Group 7 elements increase down the group? | increased number of electrons in larger atoms, the van der waals forces between molecules increase so more energy is required to separate the molecules |
| Write down five observations that would be made when sodium iodide reacts with concentrated sulfuric acid. | White fumes, Orange fumes, Colourless gas, Yellow solid, Bad Egg Smell |
| List the four steps for testing an unknown solution for halide ions | acidify with dilute nitric acid, add a few drops of silver nitrate solution, treat any precipitate with dilute ammonia solution, if a precipitate still exists, add concentrated ammonia solution |
| Explain in terms of the changes in oxidation number why the reaction of Chlorine and cold aqueous sodium hydoride is an example of a DISPROPORTIONATION reaction. | Chlorine changes from 0 to -1 and 0 to +1 in the same reaction. |
| What is the chemical test for chlorine? | Blue litmus will be turned red then decolourised in chlorine water |
| Why is the reaction of chlorine with water called a DISPROPORTIONATION reaction? | Because chlorine is simultaneously oxidised and reduced. |
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thomjj
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