AS-level AQA Chemistry questions and answers

What is the charge of a proton? - ANSWERS +1 What is the charge of a neutron? - ANSWERS 0 What is the charge of an electron? - ANSWERS -1 What is the mass of a proton? - ANSWERS 1 What is the mass of a neutron? - ANSWERS 1 What is the mass of an electron? - ANSWERS 1/1800 What is an isotope? - ANSWERS Isotopes of an element are atoms with the same number of protons but different numbers of neutrons. Why do isotopes of an element all have the same chemical properties? - ANSWERS This is because chemical properties are decided by the number and arrangements of electrons and all isotopes of an element have the same number of electrons. Why do isotopes of an element have different physical properties? - ANSWERS This is because physical properties are decided by the mass number and isotopes of an element have different mass numbers. What is the first stage in time of flight mass spectrometry and what are the 2 ways it can occur? - ANSWERS 1. Electron spray ionisation 2.Electron impact ionisation What is electron spray ionisation? - ANSWERS The sample is dissolved and pushed through a small nozzle at high pressure. A high voltage is applied to it causing each particle to gain a + ion so that the gas is made up of positive ions. What is electron impact ionisation? - ANSWERS The sample is vaporised and an electron gun is used to fire high energy electrons which knocks of 1 electron of each particle so they become positive ions. What is the second stage in time of flight mass spectrometry? - ANSWERS Acceleration What happens in the acceleration stage of time of flight mass spectrometry? - ANSWERS The positively charged ions are accelerated by an electric field so that they all have the same kinetic energy which means that the lighter ions will move faster than the heavier ions. What is the third stage in time of flight mass spectrometry? - ANSWERS Ion drift What happens in the ion drift stage of time of flight mass spectrometry? - ANSWERS The ions enter a region with no electric field, so they just drift through it. Lighter ions will drift through faster than heavier ions. What is the final stage of time of flight mass spectrometry? - ANSWERS Detection What happens in the detection stage of time of flight mass spectrometry? - ANSWERS Because ions have a lower mass/charge ratio travel at a higher speed in the drift region, they reach the detector in less time than ions with a higher mass/charge ratio. The detector detects charged particles and a mass spectrum is produced. What is the electronic configuration of calcium? - ANSWERS 1s2,2s2,2p6,3s2,3p6,4s2 What is the electronic configuration of chromium? - ANSWERS 1s2,2s2,2p6,3s2,3p6,3d5,4s1 What is the first ionisation energy? - ANSWERS The first ionisation energy needed to remove one electron from each atom in 1 mole of gaseous atoms to form 1 mole of +1 gaseous ion.. How does nuclear charge affect ionisation energy? - ANSWERS More protons means more positively charged means the stronger the attraction for electrons. How does distance from the nucleus affect ionisation energy? - ANSWERS The closer the electron is to the nucleus, the stronger the attraction. How does shielding affect ionisation energy? - ANSWERS As the number of electrons between outer electrons and the nucleus increases, the outer electron feels less attraction towards the nuclear charge. What is the trend in ionisation energy down a group? - ANSWERS The first ionisation energy down a group has a general decrease because down a group each element has an extra electron shell compared to the one above so the extra inner shells will shield the outer electrons from the nucleus attraction. What is the trend in ionisation energy across a period? - ANSWERS The first ionisation energy across a period has a general increase because it gets harder to remove outer shell electrons. What is the definition of relative atomic mass (Ar)? - ANSWERS The relative atomic mass is the average mass of an atom of an element on a scale where an atom of carbon-12 is 12. What is the definition of relative molecular mass (Mr)? - ANSWERS The relative molecular mass is the average mass of a molecule on a scale where an atom of carbon12 is 12. What is the Avogadros Constant? - ANSWERS The number of particles in a mole which is equivalent to 6.02 x 10^23. What is an equation for number of moles involving mass and Mr? - ANSWERS number of moles = mass / Mr What is an equation for number of moles involving concentration and volume? - ANSWERS number of moles = concentration x volume What is an equation for number of particles involving number of moles and Avogadros constant? - ANSWERS number of particles = number of moles x Avogadros constant What is the Ideal Gas Equation? - ANSWERS PV = nRT What is P in regards to the Ideal Gas Equation and what is its units? - ANSWERS P = nRT / V pressure and is measured in Pa or Pascals What is V in regards to the Ideal Gas Equation and what is its units? - ANSWERS V = nRT / P volume and is measured in m^3 What is n in regards to the Ideal Gas Equation? - ANSWERS n = PV / RT number of moles What is R in regards to the Ideal Gas Equation? - ANSWERS R = 8.31K^-1mol^-1 gas constant What is T in regards to the Ideal Gas Equation? - ANSWERS T = temperature and is measured in K or kelvin ( 273 + Celsius) How do you work out empirical formula? - ANSWERS / Mr e by the smallest number How do you work out molecular formula? - ANSWERS total mass / Mr ply answer by empirical formula What is the equation for percentage atom economy? - ANSWERS atom economy % = mass of desired product / total mass of reactants x 100 Why are high atom economy processes better? - ANSWERS They produce less waste and make more efficient use of raw materials so are less expensive. How do you convert m^3 into dm^3? - ANSWERS x1000 How do you convert dm^3 into cm^3? - ANSWERS x1000 How do you convert cm^3 into dm^3? - ANSWERS /1000 How do you convert dm^3 into m^3? - ANSWERS /1000 What is ionic bonding? - ANSWERS The electrostatic attraction between oppositely charged ions in a lattice. When are ions formed? - ANSWERS When one or more electrons are transferred from one atom to another. What is the charge on a sulfate ion (SO4)? - ANSWERS 2- What is the charge on a hydroxide ion (OH)? - ANSWERS - What is the charge on a nitrate ion (NO3)? - ANSWERS - What is the charge on a carbonate ion (CO3)? - ANSWERS 2- What is the charge on an ammonium ion (NH4)? - ANSWERS + What are ionic compounds made up of? - ANSWERS A positively charged and negatively charged part. What is the overall charge of a compound? - ANSWERS 0 (neutral) What is covalent bonding? - ANSWERS A shared pair of electrons where molecules are held together by strong covalent bonds. What is metallic bonding? - ANSWERS The attraction between delocalised electrons and positive ions arranged in a lattice. What is an ionic crystal structure? - ANSWERS A lattice of positive ions each surrounded in a regular arrangement by negative ions with strong ionic bonds between them so a lot of energy is needed to break them. What is the structure of a sodium chloride compound? - ANSWERS Ionic crystal structure. What are ions? - ANSWERS Charged particles. When can ions conduct electricity? - ANSWERS When liquid or molten because the ions are free to move. Why are metals ductile and malleable? - ANSWERS There are no direct bonds between metal ions so they can slide over each other. What is a giant metallic structure? - ANSWERS A regular lattice of positively charged metal ions held by a cloud of delocalised electrons. Why do giant metallic structures have a high melting point? - ANSWERS Because of strong metallic bonds. What is the structure of the magnesium? - ANSWERS Giant metallic structure. What is a macromolecular structure? - ANSWERS One in which large numbers of atoms are linked into a regular 3D arrangement by covalent bonds. Why do macromolecular structures have high melting points? - ANSWERS Strong covalent bonds. What is the structure of graphite? - ANSWERS Macromolecular: strong covalent bonds hold layers together. weak forces had layers. What is the structure of diamond? - ANSWERS Macromolecular with a tetrahedral shape. What is the structure of silicon dioxide? - ANSWERS Macromolecular or giant covalent structure. What is a simple molecular structure? - ANSWERS Small grouped atoms strongly held together by covalent bonding with weak intermolecular forces between molecules. Why do simple molecular structures have low melting points? - ANSWERS weak van der waal forces. Why do simple molecular structures not conduct electricity? - ANSWERS They have no free energy carriers. What is a charge cloud? - ANSWERS An area where electrons whizz around inside the charge cloud. What exist as charge clouds? - ANSWERS Bond pairs and lone pairs of electrons exist as charge clouds. Why do charge clouds repel each other? - ANSWERS Electrons are all-charged so the charge clouds will repel each other as much as possible so the electron pairs in the outer electron will sit as far apart as possible. What are the biggest pair-pair ratio angles? - ANSWERS Lone pair to lone pair. What are the second biggest pair-pair ratio angles? - ANSWERS Lone pair to bond pair. What are the smallest pair-pair ratio angles? - ANSWERS Bond pair to bond pair. What is electron pair repulsion theory? - ANSWERS The shape adopted is the one which keeps repulsive forces at a minimum. What is the shape and bond angles of a compound with 2 bond pairs? - ANSWERS Linear and 180 degrees. What is the shape of BeCl2? - ANSWERS Linear What is the shape and bond angles of a compound with 3 bond pairs? - ANSWERS Triganol planar and 120 degrees. What is the shape and bond angles of a compound with 4 bond pairs? - ANSWERS Tetrahedral and 109.5 degrees. What is the shape and bond angles of a compound with 5 bond pairs? - ANSWERS triganol bipyramidal and either 120 degrees or 90 degrees. What is the shape and bond angles of a compound with 6 bond pairs?` - ANSWERS Octahedral and 90 degrees. What is the shape of BF3? - ANSWERS Triganol planar. What is the shape of CH4? - ANSWERS Tetrahedral. What is the shape of PF5? - ANSWERS Triganol bipyramidal. What is the shape of SF6? - ANSWERS Octahedral What is the shape and what are the bond angles reduced from and to in a structure with 3 bond pairs and 1 lone pair? - ANSWERS Pyramidal and the angles are reduced from 109.5 to 107 degrees. What is the shape and what are the bond angles reduced from and to in a structure with 2 bond pairs and 2 lone pairs? - ANSWERS Bent and the angles are reduced from 109.5 to 104.5 degrees. What is the shape of ammonia and why? - ANSWERS Pyramidal because it has 3 bond pairs and 1 lone pair. What is the shape of water and why? - ANSWERS Bent because it has 2 bond pairs and 2 lone pairs. What is the shape of carbon dioxide and why? - ANSWERS Linear becaus