VIEWS: 28 PAGES: 19 POSTED ON: 9/17/2011
QUESTION ONE: Atomic Structure (a) A neutral atom of aluminium has an atomic number of 13 and an atomic mass of 27. (i) How many protons are there in the nucleus of the neutral aluminium atom? (ii) How many neutrons are there in the neutral aluminium atom? (iii) How many electrons will the aluminium atom lose to form an aluminium ion? (b) How many atoms are present in Zn(HCO3)2 ? (c) How many elements are present in Zn(HCO3)2 ? (d) How many atoms are there in 2 K2SO4 The pH values of four substances are given below: Sulfuric acid pH = 1 Lemonade pH = 4 NaHCO3 solution pH = 9 (e) When red and blue litmus paper is added to these three solutions what would be observed? (i) Sulfuric acid (ii) Lemonade (iii) NaHCO3 solution (f) When Universal Indicator solution is added to each of these substances, what colour would result? (i) Sulfuric acid (iii) Lemonade (iii) NaHCO3 solution 1 PERIODIC TABLE 2 H He hydrogen helium 1 4 3 4 5 6 7 8 9 10 Li Be B C N O F Ne lithium beryllium boron carbon nitrogen oxygen fluorine neon 7 9 11 12 14 16 19 20 11 12 13 14 15 16 17 18 Na Mg Al Si P S Cl Ar sodium magnesium aluminium silicon phosporus sulfer chlorine argon 23 24 27 28 31 32 35 40 19 20 K Ca 6 atomic number symbol potassium calcium name C 39 40 carbon 12 mass number Question 2. Use the Periodic Table provided to help you answer this question. What is the: (a) atomic number of fluorine? (b) mass number of phosporus? (c) symbol for potassium? (d) What is the name of the atom with a mass of 14? (e) Explain how you can use the atomic number and mass number of argon to determine the number of neutrons that it has. (f) Copy and complete the diagram to show how the electrons would be arranged around the nucleus of this atom. S (g) Explain why the charge on the S ion is -2. QUESTION THREE: (a) A sample of oven cleaner out of a can has a pH = 11. (i) What does this tell you about the nature of oven cleaner? (ii) Explain your answer to (i). (b) When baking soda (NaHCO3) is added to a sample of vinegar a reaction occurs. (i) Give the names of the elements present in baking soda. (ii) State what would be observed as the reaction proceeds. (iii) Name two products of the reaction between baking soda and vinegar. (c) The formula for magnesium chloride is MgCl2. If the charge on the magnesium ion is 2+ (Mg2+) explain how we can determine the charge on the chloride ion. (d) A potassium atom has 19 electrons. What is its electron configuration? (e) A neon atom has 10 electrons. (i) What is its electron configuration? (ii) Explain why (using your answer to (i)) neon is unreactive. Mighty Metals Copper, magnesium and aluminium metals have a number of uses in aircraft construction 1. Name a physical property of aluminium that makes it suitable for use in aircraft. 2. Name a chemical property of aluminium that makes it useful for aircraft construction. 3. Write the equation for the reaction of magnesium and hydrochloric acid Magnesium is used in emergency signaling flares 4. Explain why the chemical properties of magnesium metal make it useful for emergency signaling flares. 5. Discus why aluminium is used as a bare metal, while iron is often painted before use. In your discussion, relate the chemical properties of iron and aluminium to named uses. Fiona has found two unlabelled objects A and B. She knows that one is a metal and the other is not. She listed some properties of the objects in the table below. Objects A B Appearance Dull, black Conductivity of Good heat Malleability Good Brittle 1. Predict which of A or B Is the metal. 2. Predict the appearance of A. Marble is a rock made up of the compound Calcium Carbonate Geologists test to see if a rock is marble by placing a drop of hydrochloric acid on the rock. 1. What are the products of the reaction above? 2. Describe what the geologist might observe to confirm that a rock is Calcium Carbonate. 3. Explain how acid rain would damage a marble statue Upset tummy. 1. Give the name and formula of the metal compound formed when sulfuric acid reacts with sodium hydroxide. Name: Formula: 2. Magnesium hydroxide is a component of some antacid tablets. Name the two products of the reaction between magnesium hydroxide and hydrochloric acid found in the stomach. 3. Holly takes a beaker with 50 mL of water, stirs in a crushed antacid tablet and adds a little universal indicator. She then adds Hydrochloric acid drop by drop and notes that the colour of the solution changes from blue to green to red. Explain the colour changes above in terms of the substances added to the beaker and the products of their reaction 1. Copper and aluminium metals have a number of uses around the home. One use of copper metal is in kitchen saucepans. (a) Name TWO physical properties of copper that make it suitable for use in saucepans. Copper metal can react with oxygen in the air. (b) Write a word equation for the reaction of copper with oxygen. Copper can also be used for water pipes. (c) Explain why the chemical properties of copper metal make it able to be used for water pipes. (d) Another metal is calcium. Both aluminium and calcium are high on the reactivity series. Discuss why aluminium is often used as pure metal while calcium is not usually used as a pure metal. 2. Fiona has found two unlabelled solution bottles. She knows that one is sulfuric acid and the other sodium hydroxide. She decides to test the two solutions to find out which is the acid. She has a dropper bottle containing universal indicator. (a) Describe how Fiona could identify which bottle contains acid. Fiona’s teacher told her that another bottle contains a solution of potassium hydroxide. (b) Describe and explain what Fiona would observe if she added both red and blue litmus to potassium hydroxide. Below is the pH scale. 1 7 14 red orange green blue purple An unknown chemical turns yellow when a few drops of universal indicator are added. (c) What would be the predicted pH? (d) What does the yellow colour tell you about the unknown chemical? Ions: Mg2+ O2- H+ Cl- Magnesium is often used in school laboratories because it is a reactive metal. a) Name TWO metals that are more reactive than magnesium. b) Magnesium metal burns well in air. (i) Write a word equation for this reaction (ii) Write a balanced chemical equation for this reaction. c) Magnesium metal also reacts with hydrochloric acid. (i) Write a word equation for this reaction (ii) Write a balanced chemical equation for this reaction. d) Discuss what would happen to the pH of the acid solution in c) as more magnesium is added. Your answer should refer to the species present and what is happening in the reaction. e) Some students are making jewellery in their technology classes. They need to choose a suitable metal to make a bracelet. One student, Terri, decides to use magnesium because it is very light. Another, Fred, says he thinks that copper would be much better because it is a good conductor of heat. Discuss the suitability of each metal for making a bracelet. Refer to the ideas of Terri and Fred and use other properties of magnesium and copper in your answer. Ions: Mg2+ Ca2+ CO32- OH- H+ Cl- Increased concentrations of acid in the stomach can cause indigestion. a) Describe what will happen to the pH value of the stomach contents when the concentration of acid in the stomach is increased. “AntiAcid” is an antacid in tablet form for treating indigestion. The antacid treatment can neutralise the acid. The antacid treatment tablet contains the two metal compounds, magnesium hydroxide and calcium carbonate. b) Give the formula for: (i) Calcium carbonate (ii) magnesium hydroxide c) What would be observed when calcium carbonate and acid react together? d) What colour would litmus solution turn when drops of it are put onto some magnesium hydroxide? Give a reason for your answer. Stomach acid is hydrochloric acid. e) Write a balanced equation for the reaction of calcium carbonate with stomach acid Discuss why the reaction between magnesium hydroxide and stomach acid (hydrochloric acid) can be called a neutralization reaction. You may use equations in your answer and you should refer to the species present. Scrap metal dealers buy unwanted metal items and, after sorting them, sell them to foundries where the metals are melted down and made into new useful items. (a) State TWO physical properties of metals. (b) A common item in the scrap metal yard is the car radiator. Most are made of either aluminium or copper. When a customer brings in a radiator, the scrap metal merchant must be able to recognise the metal it is made of. This old car radiator could be made of aluminium or copper. (i) Copy and complete the table below to show the properties of aluminium and copper that can be used to tell them apart. Property Aluminium Copper Colour Low Moderate The radiator is part of the car’s cooling system. Water circulates round the hot engine, then passes through the many narrow tubes of the radiator where it cools. (ii) Discuss the suitability of these two metals for use in car radiators. (d) Sodium metal is too reactive for common use because it reacts with water. (i) What gas is produced when sodium reacts with water? When a small piece of sodium metal is dropped into a beaker of water containing litmus solution, a dark blue trail is left where the sodium has been (as shown in the photograph). (ii) Account for the formation of the blue trail. (iii) Write a balanced chemical equation for the reaction between sodium and water. An element has an atomic number of 16 and a mass number of 32. (a) Name the element. (i) Complete the table showing the number of protons, neutrons and electron in an atom of this element. Number of protons Number of neutrons Number of electons (ii) In what group of the Periodic Table is this element found? (iii) What is the charge on the ion formed by this element? Give a reason for your answer. (b) A particle of element X has 13 protons, 14 neutrons and 10 electrons. (i) Write the electron configuration for this particle. (ii) Complete the symbol for particle X showing its atomic number, mass number and charge (if any). X (c) Household bleach is a dilute solution of sodium hypochlorite, NaOCl. The hypochlorite ion is also found in calcium hypochlorite (bleaching powder) which is used to kill microbes in swimming pools. Use the Table of ions in your book to write the symbol/formula for (i) the sodium ion (ii) the hypochlorite ion (iii) calcium hypochlorite (b) Household bleach reacts with acidic liquids to release poisonous chlorine gas. This is a particular hazard in the bathroom, because some shower and toilet cleaners are acidic. (i) The table below shows the pH values of certain bathroom products. Sani-blue Plus Chemseptic Liquiscrub Bufferall pH 11.5 7.0 9.0 2.5 (i) Which product is not suitable to use with bleach? The bathroom cleaners listed above were tested using pieces of red and blue litmus paper. (ii) Copy and complete the following table showing the colour of each piece of litmus paper AFTER it had been dipped into the cleaner. Sani-blue Plus Chemseptic Liquiscrub Bufferall Colour of red litmus paper Colour of blue litmus paper A scientist investigating the site of an ancient civilisation finds 6 objects (A – F). She analyses the objects and sends her notes back to the University she works for. Unfortunately some of the information she collected was lost. The table below shows the information that was received. A blank square indicates there was no information available for that particular property. Objects Appearance Conductivity Conductivity Malleability of heat of electricity A Shiny, brown Good B Good Good C Good Poor Brittle D Dull surface, shiny Good when cut E Good Good F Dull black surface Good Brittle Assuming the objects were made from elements, use the information given above to identify if they are metals or non-metals. Copper is used for electrical wires. Give 2 physical reasons and 1 chemical reason why wire is suitable for this purpose. Iron nails are often galvanized. Explain what the process of galvanizing involves and how the process works. Give the name and formula of the metal compound formed when sulfuric acid reacts with calcium hydroxide. 5. Magnesium hydroxide tablets are used to reduce stomach acidity. a) What happens to the pH of an acid solution when Magnesium hydroxide is added? b) Write a balanced chemical equation for the reaction between magnesium hydroxide and hydrochloric acid (stomach acid) Reactivty Series of Metals Name Symbol Sodium Na Calcium Ca Magnesium Mg Aluminium Al Zinc Zn Iron Fe Lead Pb Copper Cu A manufacturer of Mountain bikes decided to make the frames out of Aluminium. a) Give a physical reason and a chemical reason why Aluminium is suitable for making bike frames out of. The manufacturer decided to use either Magnesium or Zinc to coat his Aluminium frames with. Use the reactivity series given above to answer the following questions. b) Which would be the best metal (out of Zinc or Magnesium) to coat the frames with? c) The reason that the metal based paint I chose in b) is the best is because; d) Why wouldn’t sodium be a suitable metal to use as a coating for the mountain bike frames? When the manufacturer went to his warehouse to get the metal he had chosen he discovered that a water leak had caused the labels on 4 boxes of different metals to wash off. He decided to find out which was which by carrying out a series of tests. He discovered: Metal A did not react with hot or cold water or dilute hydrochloric acid. Metal B reacts with hydrochloric acid but not water Metal C reacts with hydrochloric acid and reacts slowly with hot water. Metal D reacts with hydrochloric acid, hot water and cold water. e) If the four boxes originally contained zinc, copper, calcium and magnesium match the box to its contents. Positive Ions Negative Ions 1+ 2 + 3 + 1- 2- 3- H1+ Fe2+ Fe3+ Cl1- CO32- PO43- hydrogen Iron (II) ion Iron (III) ion Chloride ion Carbonate Phosphate ion ion ion K1+ Mg2+ Al3+ NO31- O2- Potassium Magnesium Aluminium Nitrate ion oxide ion ion ion ion Na1+ Ca2+ HCO31- S2- Sodium ion Calcium ion hydrogen carbonate Sulfide ion ion NH41+ Zn2+ OH1- SO42- Ammonium Zinc ion Hydroxide ion Sulfate ion ion Ag1+ Pb2+ Silver ion Lead ion Cu2+ Copper (II) ion Identify the following ionic compounds. a) Ca(Cl)2 b) Pb(OH)2 c) Al2O3 Use the table of ions provided to give the formula for the following ionic compounds. a) Calcium carbonate b) Sodium chloride c) Iron(III) hydroxide d) Copper nitrate Name the products for the following reactions a) Iron + oxygen gas b) Zinc + hydrochloric acid c) Copper oxide + nitric acid Name the reactants that where reacted together to form the following products. a) Lead sulfate, carbon dioxide and water b) Calcium chloride + hydrogen gas Kieran had an iron can covered with rust (iron (II) oxide). He decided to clean the can by dipping it into a beaker of dilute hydrochloric acid. He figured that the acid would eat through the rust layer first. The acid solution contained a few drops of universal indicator. When he carried out the experiment he made the following observation: The colour of the solution changed to a green colour. No gas was given off. a) What does the (II) in the expression iron (II) oxide mean? b) What was the original colour of the acid solution with universal indicator? c) Give a word equation to describe the reaction that was occurring c) Write a balanced chemical equation for the reaction. Kieran noticed that the rust was gone from the iron can. However he decided to add some sulfuric acid to the beaker containing the can. When he did so he observed that 1. The solutions colour changed to a bright red. 2. After a few minutes, bubbles of gas started to be given off. 3. A white solid began to form on the sides of the can. 4. After a few more minutes the bubbles stopped. 5. The solution had changed to a slightly pink colour. d) For each statement explain the observations given e) Describe the chemical test used to test for the gas produced in the reaction above The word equation for a chemical reaction is given below Acid + Base A metal salt + water a) Give a definition of the word base b) Copy and complete the general word equations given below (i) Acid + Metal Carbonate (ii) Acid + Metal c) Describe the chemical test used to test for the gas produced in the acid + carbonate reaction. Corrosion (rusting) occurs more rapidly in areas where the air is polluted. This is because when non-metals such as carbon or sulfur are burnt they form non-metal oxides that react with water in the atmosphere to form a weak acid solution (acid rain) d) What is the (approximate) pH of the weakly acidic acid rain. The acid rain that falls eats away at limestone buildings and statues. This is because limestone is made up of calcium carbonate. e) Write a balanced equation for the reaction that occurs between the calcium carbonate in the statues and sulfuric acid (which is one of the acids in acid rain) (Hint: Write a word equation first and continue from that) f) A student was asked to prepare a solution of lead chloride. Write a word equation for the formation of lead chloride from an appropriate acid and another suitable substance. QUESTION ONE: ATOMIC STRUCTURE You will need to use the Periodic Table and the Table of Ions to answer these questions. (a) Copy and complete the table below by putting the appropriate numbers or symbols into all the boxes. Electron Mass Name Symbol Protons Neutrons Electrons arrangement number Aluminium 27 Argon 22 Chloride 35 ion (b) Explain why the magnesium ion has a 2+ charge. (c) Complete the table below by putting in the appropriate name or compound formula. Your answers below Magnesium hydroxide Ca(HCO3)2 Lead nitrate Li2SO4 Iron (III) carbonate BaCl2 (d) How many atoms of oxygen are there in the formula Al2(CO3)3? (e) What is the total number of atoms in the formula Al2(CO3)3? QUESTION TWO: METALS AND COMPOUNDS (a) Sebastian was required to investigate physical properties of two different substances. Substance A was calcium and substance B was calcium carbonate (limestone). Sebastian said calcium was a ductile substance Describe what this means. (b) Discuss how both substances would behave when connected to an electrical circuit as shown. Give reasons for their behaviour. Substance A (c) Explain why calcium is not a suitable metal to use in an electrical circuit. (d) Both substances A and B can be used to make calcium chloride. Write a word equation for the reaction of calcium carbonate that will form calcium chloride. It is not recommended for calcium to be put into acid. However it can be put into water relatively safely. A piece of calcium is put into water containing universal indicator. (e) Describe the colour of the universal indicator before the calcium was put in. (f) Write a balanced symbol equation for the reaction of calcium with water (universal indicator is not included in the equation). (g) Describe and explain the observations you would make as the reaction proceeds and relate them to the chemical changes taking place. (h) Lead is used within the keels of boats and aluminium is used for a number of the fittings on the boat. Pure aluminium is much more reactive than pure lead. Discuss two reasons (one physical and one chemical) why aluminium is a suitable metal for the fittings. Physical reason Chemical reason (i) Explain two reasons (one physical and one chemical) why lead is used for the keel. Physical reason Chemical reason QUESTION THREE: ACIDS AND BASES Mohutu and Chi are in their baking class. The first task of the day is to follow a recipe to make a banana cake. The ingredients in the recipe are shown below. Flour bananas baking powder baking soda eggs water Milk butter vanilla essence (a) At the end of the lesson, Mohutu says their cake is too hard. Chi points out the obvious, that the cake had not risen. Which ingredient(s) did the students probably leave out of their cake? (b) One of the listed ingredients is called baking soda. What is its chemical name? (c) Early in the recipe the mashed bananas are mixed with warm milk. This mixture is weakly acidic. What would be the observation if two types of litmus paper (red and blue) were dipped into this milk-banana mixture? Red litmus paper Blue litmus paper (d) Describe the pH of the milk solution (e) Describe what happens when this weakly acidic mixture comes in contact with baking soda in the cake recipe. Explain your observations. (f) In another lesson, Mohutu and Chi had to cook eggs in an iron frying pan. Give reasons why iron is a suitable material for use in a frying pan.
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