As-Level Chemistry Paper 1 Questions and answers

As-Level Chemistry Paper 1 Questions and answers First Ionisation Energy down Group 2 Alkali Metals First ionisation energy down Group 2 Alkali Metals goes as follows: 1) The ionisation energy decreases as you go down the group 2) This is due to their being extra shielding for the outermost electrons the further down the group you go as well as the further distance between the outer electrons 3) These two occurrences out weigh the power of the increasing positively charged nucleus as you go down the group How does reactivity change in group 2 elements Some of the ways that reactivity changes in group 2 elements are as follows: 1) Their is an increase as you go down the group 2) This is because the ionisation energy needed to carry out a reaction is lower the further down the group you go - This means you don't have to put in much energy for a reaction to take place if the element you select is one of the obese further down this group Melting point of group 2 metals The melting points of group 2 metals goes as follows: 1) Overall the melting points of these metals decrease as you go down the group 2) This is because, thought the metal ions get bigger, the number of delocalised electrons and the charge on the ion doesn't change to keep thing equivalent 3) This larger ionic radius therefore causes the distance between the ions and the electrons to increase as their are not as many electrons that are able to get just as close a previously 4) This means that it takes less energy to break the bonds, which means that the melting point generally decrease as you go down the group - Though this is not the case for Mg where it melting point is really lower in comparison to those around them 5) The reason for Mg being different is that the arrangement of the metallic ions change How do group 2 metals react with water? The way that group 2 metals react with water goes as follows: 1) When group 2 metals react, they are oxidised from a state of 0 to +2 2) This means that when they react with water, a metal hydroxide and hydrogen gas is produced 3) This reaction happens more rapidly as you go down the group due to the ionisation energy decreasing 4) However, it is important to remember that Beryllium does not react with water as its ionisation energy is to high Solubility of group 2 metals The solubility of group 2 metals goes as follows: 1) This heavily depend on the anion the group 2 metal is attached to 2) If they are connected to OH-, solubility increases down the group as they are connected to a singly charged negative ion 3) If they are connected to SO4^2- solubility decreases as you go down the group as they are connected to a doubly charged negative ion barium sulfate What group 2 metal sulfate is insoluble in water Test for sulfate ions To test for sulfate ions you do as follows: 1) Pour you solution containing sulfate ions into a test tube 2) Use a pipette to add hydrochloric acid and barium chloride to the solution 3) If sulfate ions are present a barium sulfate white precipitate will form Use of group 2 metals Some of the uses of group 2 metals are: 1) Barium meals 2) Extraction of titanium 3) Removal of sulfur dioxide from flue gases 4) Acid neutralisers Barium meals Barium meals goes as follows: 1) When using X-rays, a doctor can use the machine to detect for where bones are and whether they are broken or not 2) However, this is not beneficial however should you be looking for soft tissues as they do not show up 3) Therefore 'barium meals', made up of suspended barium sulfate, are given to the patient to help diagnose problems with the oesophagus, stomach or intestines by showing the outlines of these tissues 4) You could only use barium sulfate for this task due to other solutions being poisonous Extraction of titanium The extraction of titanium goes as follows: 1) Magnesium is used as part of the process of extracting the titanium from its impure ore 2) First the ore, TiO2 is converted to titanium(IV) chloride, TiCl4 by heating it with carbon in a steam of chlorine gas 3) The TiCl4 is then purified through fractional distillation before being reduced by Mg in a furnace at almost 1000 'C Removal of sulfur dioxide from flue gases The removal of sulfur dioxide from flue gas is important when burning fossil fuels to produce electricity as sulfur dioxide pollutes the atmosphere. The system works as follows: 1) A slurry of calcium carbonate and water is produced 2) When Sulfur dioxide react with this, calcium sulfite is produced which cannot pollute the atomsophere Group 2 metals and neutralising acids Groups 2 metals can neutralise acids due to the following: 1) Due to being an alkaline earth metal, the elements can be used to neutralise acids 2) An example of this is calcium hydroxide which neutralises acidic soils 3) Another example of this is Magnesium hydroxide which is used as an antacid to neutralise stomach acid Group 7 halogens and boiling points Group 7 halogens and boiling points go as follows: 1) The boiling point increases as you go down the group 2) This is due to their being greater Van der Waals forces as the size and relative mass of the molecules increases - This helps to explain why F is a gas at room temperature whereas I is a solid Group 7 Halogens and electronegativity Groups 7 halogens and electronegativity goes as follow: 1) Electronegativity decreases down the group 2) Though all halogens are extremely electronegative, the larger atoms attract electrons less than smaller ones 3) This is because their outer electrons are further from the nucleus and more shielded because they have more inner electrons F2, pale yellow, gas Formula, colour, physical state of Fluorine Cl2, green, gas Formula, colour, physical state of Chlorine Br2, red-brown, liquid Formula, colour, physical state of Bromine I2, grey, solid Formula, colour, physical state of Iodine Group 7 halogens and displacement reactions Group 7 halogens and displacement reactions goes as follows: 1) When the halogens react, they gain an electron - This means that they are oxidising agents 2) They get less reactive down the group, because the atoms become larger and the outer shell gets further from the nucleus - So the halogens become less oxidising down the group 3) This means that when a halogen reacts with a solution containing a halide ion, the stronger oxidising halogen will become part of the solution - This means that a halogen will replace a halide from its solution if the halide is below it in the periodic table 4) These reactions are therefore useful when trying to identify which halogen is present in a given solution as the displaced halide will give off that particular halogens distinct colour - e.g. bromine ions will turn the colour brown Uses of halogens Some of the uses of halogens goes as follows: 1) Making bleach 2) Chlorine and water 3) Water treatment The process of making bleach The process of making bleach goes as follows: 1) When chlorine gas is reacted with cold, dilute sodium hydroxide at room temperature, you get sodium chlorate(I) solution (NaClO) - This is commonly known as bleach 2) In this reaction, Chlorine oxidation state become +1 when producing bleach. However, it sodium chloride is also being producing in this reaction alongside H2O. This means that the other chlorine is being reduced with an oxidation state of -1 3) When an element is being reduced and oxidised, like chlorine, the process is known as disproportionation When an element is being oxidised and reduced in a single chemical reaction Disproportionation definition Reacting Chlorine and water The process for reacting chlorine and water goes as follows: 1) When you mix chlorine with water, it undergoes disproportionation, leaving you with a mixture of chloride ions and chlorate(I) ions 2) In sunlight, chlorine can also decompose water to form chloride ions and oxygen Chlorine or a compound containing Chlorate(I) ions What do you add to water to treat it Advantages of treating water with chlorine Some of the advantages of treating water with chlorine are: 1) It kills disease-causing microorganisms in the short-term and long-term as remnants of chlorine remain in the water - This stops the water getting reinfected 2) It prevents the growth of algae and remove discolouration caused by organic compounds Disadvantages of treating water with chlorine Some of the disadvantages of treating water with chlorine are: 1) Chlorine gas can cause harm to your respiratory system 2) Chlorine liquid can cause harm to you skin or eyes through burns 3) Chlorine can react with the organic compounds in the water to produce chlorinated hydrocarbons which can cause cancer - Though this possibilities is less dangerous than a possible cholera epidemic from not treating water Group 7 halogens and being reducing agents Some facts about group 7 halogens and being reducing agents are as follows: 1) As you go down this group, the attraction between the nucleus and electron gets weaker - This is due to greater distances between the nucleus and electrons as well as greater shielding 2) This therefore means the power of a halogen to act as a reducing agent increases down the group 3) A great way of seeing this is reacting sulphuric acid with a sodium halide - The best reducing halogens are able to turn the substance into H2S Reacting sulfuric acid with sodium chloride or fluoride Reacting sulfuric acid with sodium chloride or fluoride goes as follows: 1) The products of this reaction are hydrogen fluoride/chloride and sodium hydrogen sulfate 2) Due to HF and HCl not being powerful reducing agents the reaction stops here with the oxidation states of the halide staying the same (-1 and +6) Overall the reaction goes as follows: Na(F/Cl) + H2SO4 — NaHSO4 + H(F/Cl) Reacting sulfuric acid with sodium bromide Reacting sulfuric acid with sodium bromide goes as follows: 1) The products of this reaction are Hydrogen Bromide and Sodium Hydrogen Sulfate 2) However, because the HBr is a strong enough reducing agent it is able to continue its reaction with NaHSO4 to produce bromine sulfur dioxide and water 3) Due to this the oxidation states of bromine and sulfur change (going from -1 and +6 to 0 and +4) The overall reaction goes as follows: NaBr + H2SO4 — NaHSO4 + HBr | — | 2HBr + H2SO4 — Br2 + SO2 +2H2O Reacting sulfuric acid with sodium iodide Reacting sulfuric acid with sodium bromide goes as follows: 1) The initial reaction produces Hydrogen Iodide and Sodium Hydrogen Sulfate 2) The HI then reduce the sulfuric acid to produce Iodine, Sulfur Dioxide and Water 3) However, the HI then reacts again with SO2 to produce Hydrogen Sulfide, Iodine and Water 4) This lead the Iodine to be oxidised from -1 to 0 and Sulfur to reduce go from +6 to then +4 to the -2 5) The overall reaction goes as follows: NaI + H2SO4 — NaHSO4 + HI |—| 2HI + H2SO4 — I2 + SO2 +2H2O Testing for halides When testing for halides you do as follows: 1) Place you halide solution into a test tube 2) Add nitric acid to remove ions which might interfere with the test 3) Now add a few drops of silver nitrate to the solution 4) If the halide solution contains halides then precipitate of silver halide will form 5) Chlorine will produce a white precipitate whilst Bromine will produce a cream one and Iodine will produce yellow one 6) Fluorine cannot be detected however as no precipitate is formed How to use a flame test to identify group 2 metals To identify group 2 metals through a flame test you do as follows: 1) Dip a nichrome wire loop in concentrated hydrochloric acid before dipping it the metal 2) You then place the wire under the clear blue part of the Bunsen burner until the flame changes colour 3) If the flame turns brick red it calcium, red then its strontium, pale green and its barium Test for ammonia To test for ammonia you do as follows: 1) Pour the ammonia solution into a test tube 2) Collect a strip of Red Litmus paper and dip it in distilled water and hang it over the test tube 3) The gas produced will cause the solution to produce ammonia gas - This will show ammonia is present and result in the red litmus paper going blue Test for ammonium ions To test for ammonium ions you do as follows: 1) Add dilute sodium hydroxide to a test tube containing possible ammonium ions - Heat the tube gently 2) Dampen some red litmus paper and hang it over the tube - If ammonium ions are present the paper will go blue Test for hydroxide ions To test for hydroxide ions you do as follows: 1) Pour the solution containing hydroxide ions into a test tube 2) Dip a piece of red litmus paper into the solution 3) If hydroxide ions are present the paper will go from red to blue Test for carbonate ions To test for carbonate ions you do as follows: 1) Pour the solution possible containing carbonate ions into a test tube 2) Add hydrochloric acid to the solution and place a bung over the test tube to another test tube featuring limewater 3) If carbonate ions are present, CO2 will be produced, this will then be funnelled into the lime water and cause the water to become cloudy Alkaline earth metal An element in group 2 of the periodic table Barium Chloride test Test that uses acidified barium chloride to test for sulfate ions in solution. Halide A negative ion of a halogen Halogen An element in Group 7 of the periodic table Silver nitrate test Test that uses silver nitrate solution to identify halide ions in solution Accurate result A result that's really close to the true answer Anomalous result A result that doesn't fit in with the pattern of results in a set of data Categoric data Data that can be sorted into categories Casual Link The relationship between two variables where a change in one variable causes a change in the other Continuous data Data that can have any value on a scale Control variable A variable that is kept constant in an experiment Correlation The relationship between two variables Dependent variable The variable that you measure in an experiment Discrete data Data that can only take certain values Hypothesis A suggested explanation for a fact or observation Independent variable The variable that you change in an experiment Ordered/ ordinal data Categorical data where the categories can be put in order Precise result Results where the data have a very small spread around the mean Prediction A specific testable statement about what will happen in an experiment, based on observation, experience or a hypothesis Random error An error introduced by a factor that you cannot control The Structure of an atom The Structure of an atom goes as follows: 1) Made up of three types of particles, protons, neutrons and electrons 2) The electrons can be found whizzing around the nucleus in orbital which make up the majority of the volume of an atom 3) The takes up a small volume of the atom, the nucleus of an atom is where the majority of atom's mass is held due to it contain all of the atom's protons and neutrons Atom A neutral particle made up of protons and neutrons in a central nucleus and electrons orbiting the nucleus Proton A sub-atomic particle with a relative charge of +1 and a relative mass of 1, this is located in the nucleus of an atom Neutron A sub-atomic particle with a relative charge of 0, and a relative mass of 1, this is located in the nucleus of an atom Electron A sub-atomic particle with a relative charge of -1, and a relative mass of ¹/₂₀₀₀. In atoms, this can be found in orbitals which surround the nucleus Mass number Also known as A, this is the total number of protons and neutrons in an atom. Atomic number Also known as Z, this is the number of protons in the nucleus of an atom. We can therefore use Z to find out what element an atom is as each element has a particular Z. An example of this is H which has a Z of 1, therefore each atom with the equivalence of 1 Z, is a H atom Neutral atoms Some facts about neutral atoms are as follows: 1) They have no overall charge, so therefore the amount of protons in the nucleus of the atom, is equivalent to the amount of electrons in the atom's orbitals 2) The number of neutrons found in a neutral atom is equal to the mass number (A) - the atomic number (Z) How is carbon-12 used when deciding upon a molecules Mr Carbon-12 used when deciding upon a molecules Mr because: 1) The mass of protons and neutrons for each atom varies slightly depending on how many of each particles are present - Therefore, in order to define a 'atomic mass unit' one nucleus needs to made the overall standard whereby the mass of other nucleus can be compared against 2) As a result "Carbon-12" was chosen due to its mass per nucleon being around the average of the other atoms' mass per nucleon - This means, in comparison to Carbon-12, other atoms' atomic mass are close to whole numbers 3) An example of this is when Carbon Mr=12, Hydrogen's Mr=1 in comparison Ions Some of the things you need to know about ions are as follows: 1) These are charge particles that are formed when one or more electrons are lost or gained by an atom or molecule 2) As a result of having a different number of protons and electrons in the atom, an ion can have a positive or negative charge. 3) An ion is positively charge (A Cation) when they have more protons and electrons 4) An ion is negatively charged (An Anion) when they have more electrons than protons Isotopes These are atoms with the same number of protons as the element they belong to, but have a different amount of neutrons How do the chemical properties of isotopes compare to neutral atoms The chemical properties of isotopes compare to neutral atoms as follows: 1) Isotopes have the same chemical properties as neutral atoms due to both atoms still having the same electron configuration How do the physical properties of isotopes compare neutral atoms The physical properties of isotopes compare to neutral atoms as follows: 1) Isotopes don't have the exact same physical properties as neutral atoms due to an atoms physical properties being dependent on the mass of an atom 2) Therefore, due to isotopes have more or less neutrons than typical neutral atoms, their mass numbers are different 3) An example of this is that isotopes will have a different density and rate of diffusion compared to their neutral atom counterpart Dalton's and Thomson's Atomic Model Dalton's and Thomson's atomic model go as follows: 1) At the start of the 19th Century, Dalton described atoms as solid spheres and claimed that different combinations of spheres made up different elements 2) In 1897, this was changed following evidence provided by Thomson to suggest that an atom contains small positively charge particles (protons) and even smaller, negatively charged particles (electrons). 3) Thomson therefore devised the 'plum pudding model', the diagram below. which suggested that and atom was made up of freely moving protons and electrons Rutherford's Gold Foil Experiment Rutherford's Gold Foil Experiment went as follows: 1) During a gold foil experiment in 1909, Rutherford was finding what happened when he fired alpha particles at an thing sheet of gold 2) From his knowledge of the atom, which was based off of the Plum Pudding Model, Rutherford was expecting most of the alpha particles to be deflected slightly by the gold atom 3) However, instead Rutherford found that most alpha particles weren't deflected at all, and when they were deflected, the angled at which they were was steep and resulted in the majority of the particles being deflected backwards towards them. 4) As a result, Rutherford concluded that the Plum Pudding Model couldn't be correct and instead proposed the atomic model Rutherford's atomic model Rutherford's atomic model went as follows: 1) All of an atom's protons were now found in the nucleus of the atom, the atoms' centre 2) All of an atom's electrons were now found to surround the nucleus of the model in a 'cloud' 3) The gap between the nucleus and the electrons was now known as empty space They realised that electrons in a 'cloud' around the nucleus of an atom, as Rutherford described, would quickly spiral down into the nucleus, causing the atom to collapse Why did scientists disagree with Rutherford's model Bohr's atomic model Bohr's atomic model went as follows: 1) Agreed with the atomic model and how it described protons being found in the centre of the atom in the nucleus 2) Proposed that electrons only exist in fixed energy shells (orbits) and not anywhere in between 3) Each electron shell had its fixed energy 4) When an electron moves between shells electromagnetic radiation is emitted or absorbed 5) Because the energy of shells is fixed, the radiation will have a fixed frequency History of the atomic model The history of the atomic model goes as follows: 1) Dalton's model 2) Thomson's model 3) Rutherford's gold foil experiment and the implementation of the atomic model 4) Bohr's atomic model 5) Quantum model Progression of the atomic model after Bohr's atomic model The progression of the atomic model after Bohr's model went as follows: 1) It was later discovered by scientists that not all electrons in a shell had the same energy, resulting in Bohr's model also becoming incorrect until it was refined to include sub-shells 2) Even still, though we still use Bohr's refined model due to it being able to explain the majority of observations, it to is wrong and has been replaced 3) The most accurate model now is the quantum model which is based off of the complex fundamentals of quantum mechanics. As a result it explains a lot more than Bohr's model is able to do, though it is harder to get your head around Relative atomic mass Ar, is the average mass of an atom on a scale where carbon-12 is exactly 12 Relative isotopic mass The mass of an atom of an isotope of an element on a scale where an atom of carbon-12 is exactly 12 Calculating relative atomic mass When calculating relative atomic mass you do as follows: 1) Calculate the mass numbers of the isotopes you are given and find the percentages of their abundance 2) Using the equation in the photo, plug in your values 3) Your answer will be the Ar Relative molecular mass The Mr is the average mass of a molecule when an atom of carbon-12 is exactly 12. To calculate you find the amount of each element in the molecule and add up relative atomic mass values of all the atoms in the molecule e.g, CO₂ Mr=12+16+16 which will = 42 Relative formula mass The average mass of a formula unit when carbon-12 is exactly 12. To calculate this, you add up the relative atomic masses of all of the ions in the formula unit e.g, HCl Mr=1+35.5 Which will = 36.5 Mass Spectrometer this is a machine that provides information about the relative atomic mass of an element and the relative abundance of its isotopes, or the relative molecular mass of a molecule if you use it to analyse a compound Method of mass spectrometer The method of a mass spectrometer goes as follows: 1) Ionisation - Can happen by electrospray ionisation or electron impact ionisation where the sample of isotope is turned into a gaseous positive ion 2) Acceleration - Where the positive ions are accelerated by an electric field to the same Kinetic Energy. As a result of KE=¹/₂MV², the molecules with a lower mass/charge ratio will have a higher velocity than the ions with a higher mass/charge ratio 3) Ion drift - Where in which each ion will drift through a void at their own specific velocity until they hit the ... 4) Ion detector - Where an ion hit a negatively charged plate, and gains an electron to become neutral. As a result of this process, a current is formed that is proportional to the abundance of the ion. It must be remembered that this happens to the ions with the lowest mass/charge ratio first as they have a higher velocity and will cross the void sooner Mass Spectrum A chart produced by a mass spectrometer which can give you information about the relative masses and relative abundances of particles in a sample Electrospray ionisation This is a form of ionisation used in mass spectrometers to turn solvents of elements or compounds into gaseous positive ions. What happens is as follows: 1) The sample is dissolved into a solvent and pushed through a small nozzle at a high pressure 2) A high voltage is then applied to the solvent which causes each atom to gain one proton and become a positive ion 3) the solvent is then removed, leaving a gas of positive ions ready for the remaining steps of the mass spectrometer Electron impact ionisation This is a form of ionisation used in mass spectrometers to turn a sample of elements or compounds into positive ions. What happens is as follows: 1) The sample is vaporised and then hit with an 'electron gun' which fires high energy ions at the sample 2) This will cause an electron to be removed from each particle resulting in the elements or compounds in the sample becoming positive ions ready for the remaining steps of a mass spectrometer How does a mass spectrum work for elements A mass spectrum works for elements as follows: 1) Each line will represent a different isotope of the element 2) The Y-axis of the graph will represent the abundance, often as a percentage, of the isotope 3) As a result the height of each peak will represent the relative isotopic abundance (the relative amount of each isotope present in the sample) 4) The X-axis will provide the mass/charge ratio of each isotope. It is important to remember that since the charge of an ion is mostly 1+, it cvan be assumed the the X-axis is simply the relative isotopic mass What can a mass spectrum be used to calculate Some of the things a mass spectrum can be used to calculate are the: 1) Relative atomic mass of an element 2) Relative molecular mass