12.5. Identification of ions and gases
A subsection of Chemistry, 0620, through 12. Experimental techniques and chemical analysis
Listing 10 of 359 questions
Intracellular fluid is the solution between the cells in the human body. Table 2.1 shows the masses, in mg, of some ions in 100 cm3 of intracellular fluid. Table 2.1 name of ion formula of ion mass of ion in 100 cm3 of intracellular fluid / mg calcium Ca2+ chloride Cl – hydrogencarbonate HCO3 – phosphate PO4 3– magnesium Mg2+ potassium K+ sodium Na+ sulfate SO4 2– Answer these questions using information from Table 2.1. Name the positive ion that is present in the lowest concentration. Name the ion that contains an element in Group IV of the Periodic Table. Describe a test for sulfate ions. test observations  Small amounts of ammonium ions and chloride ions are formed in some cells of the body. State the formula of the compound formed from ammonium ions and chloride ions. Choose from the list the salt that is insoluble in water. Tick (✓) one box. copper(nitrate lead(chloride potassium nitrate sodium chloride  Table 2.2 shows some properties of the Group I metals. Table 2.2 metal hardness / MPa observations on reaction with water lithium 5.0 bubbles form very slowly and no flame sodium 0.69 bubbles form very slowly and no flame potassium bubbles form very rapidly and flame rubidium 0.22 Use the information in Table 2.2 to: ● predict the hardness of potassium ● describe the observations when rubidium reacts with water.  Sodium reacts with hydrogen to produce sodium hydride, NaH. Complete the symbol equation for this reaction. 2Na + → NaH 
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THEORY
2024
Paper 3, Variant 3
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Barium sulfate, BaSO4, is an insoluble salt and is made by precipitation. Name two aqueous solutions that produce a precipitate of barium sulfate when they are mixed.  Describe how to produce a pure sample of barium sulfate from the mixture of aqueous solutions in . Write an ionic equation for the precipitation reaction which produces barium sulfate. Include state symbols. Soluble salts are made from dilute acids. Name the dilute acid and one other substance that react together to make copper(sulfate. dilute acid other substance  Nitrates decompose when they are heated. When hydrated copper(nitrate is heated, oxygen gas is produced. Describe a test for oxygen. test observations  Complete the equation for the decomposition of hydrated copper(nitrate. 2Cu(NO3)2•3H2O → CuO + NO2 + O2 + H2O Hydrated zinc sulfate gives off water when it is heated. ZnSO4•xH2O→ ZnSO4+ xH2OA student does an experiment to determine the value of x in ZnSO4•xH2O. step 1 The student weighs a sample of hydrated zinc sulfate. step 2 The student heats the sample of hydrated zinc sulfate. step 3 The student weighs the solid after heating. step 4 The student repeats step 2 and step 3 until the mass of solid after heating is constant. State why the student does step 4. In an experiment, 0.574 g of ZnSO4•xH2O is heated until the mass is constant. The mass of ZnSO4 that remains is 0.322 g. [Mr: ZnSO4, 161; H2O, 18] Determine the value of x using the following steps. ● Calculate the number of moles of ZnSO4 remaining.  mol ● Calculate the mass of H2O given off.  g ● Calculate the number of moles of H2O given off.  mol ● Determine the value of x.  x =  
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THEORY
2024
Paper 4, Variant 3
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Use The diagram shows the salt mines at Bex in Switzerland. salt solution pumped up mountain side underground reservoir sodium chloride solution rock (mainly anhydrite) layers of salt air vent The salt is dissolved by water from underground springs and then pumped up to a reservoir where it is stored as a solution. Write the chemical formula for sodium chloride. Suggest how solid sodium chloride is obtained from the sodium chloride solution. Examiner's Use Sodium chloride has an ionic giant structure. Which one of the following best describes an aqueous solution of sodium chloride? Tick one box. a mixture of sodium ions and chlorine molecules in water a mixture of sodium and chlorine atoms in water a mixture of sodium and chloride ions in water a mixture of sodium, chloride, oxide and hydrogen ions Describe a test for chloride ions. test result The rock surrounding the layers of salt is anhydrite. Pure anhydrite has the chemical formula CaSO4. State the name of the chemical found in anhydrite. Calculate the relative formula mass of the chemical in pure anhydrite. When anhydrite reacts with water, gypsum (CaSO4.2H2O) is formed. Complete the equation for this reaction. CaSO4 + CaSO4.2H2O Which one of the following describes this reaction? Put a ring around the correct answer. combustion fermentation hydration oxidation reduction Examiner's Use The chemical in anhydrite can be made by reacting calcium hydroxide with sulphuric acid. Complete the balanced equation for this reaction. Ca(OH)2 + CaSO4 + H2O The spring water running through the rocks changes anhydrite into gypsum. This reaction is exothermic. Use this information to explain why the temperature of the mine never falls below 17 oC even in cold winters. The air inside the mine contains 19% oxygen. Which one of the following best describes the oxygen level inside the mine compared with that outside the mine? Tick one box. the level of oxygen inside the mine is higher the level of oxygen is the same the level of oxygen is about a quarter of that of the outside air the level of oxygen inside the mine is lower
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THEORY
2005
Paper 2, Variant 0
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Use Copper can be extracted by heating copper carbonate with carbon. The copper carbonate breaks down into copper oxide and releases a gas. Complete the equation for this reaction. CuCO3 CuO + The copper oxide then reacts with the carbon. 2CuO + C 2Cu + CO2 heat Complete the following sentences using words from the list. endothermic exothermic halogen metal neutralised oxidised reduced In this reaction copper oxide is to copper. The copper obtained is a pinkish-brown The reaction is because heat is absorbed. State the name of the substance which is oxidised during this reaction. How would you test for the carbon dioxide given off in this reaction? test result Describe a test for aqueous copper ions and state the result. Examiner's Use Carbon is in Group IV of the Periodic Table. Draw a diagram to show how the electrons are arranged in an atom of carbon. To which Period in the Periodic Table does carbon belong? Organic compounds contain carbon and hydrogen. To which homologous series does the organic compound A belong? H H H C H H C H compound A State the name of compound A.
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THEORY
2006
Paper 2, Variant 0
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For Examiner's Use Calcium carbonate is an important raw material. Name a rock which is made up of calcium carbonate. When calcium carbonate is heated strongly, it decomposes. CaCO3 → CaO + CO2 Calculate the relative formula mass of: CaCO3 CaO 7.00 kg of calcium oxide was formed. What mass of calcium carbonate was heated? Calcium carbonate is used to control soil acidity. Why is it important to control soil acidity? Both calcium carbonate, insoluble in water, and calcium oxide, slightly soluble, are used to increase soil pH. Suggest two advantages of using calcium carbonate. Give one use of calcium carbonate other than for making calcium oxide and controlling soil pH.
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THEORY
2006
Paper 3, Variant 0
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