12. Experimental techniques and chemical analysis
A section of Chemistry, 0620
Listing 10 of 677 questions
The structures of six gases are shown below. A Ar O O O C O N N C H H H H C B C D E F Cl Cl Answer the following questions about these gases. Each gas may be used once, more than once or not at all. Which gas, A, B, C, D, E or F bleaches damp litmus paper, forms 79% of the air, is a noble gas, can undergo polymerisation, decolourises aqueous bromine, is a product of respiration? Gas F is a compound. Define the term compound. Give a use for gas E. When magnesium is heated in gas C magnesium nitride, Mg3N2, is formed. Complete the symbol equation for this reaction. Mg + → Mg3N2
0620_w15_qp_23
THEORY
2015
Paper 2, Variant 3
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The diagram shows the structures of five substances, A, B, C, D and E. A B D E C N N O S O O C O Cl – Cl – NH4 + NH4 + Cl – Cl – NH4 + NH4 + Cl – Cl – NH4 + NH4 + H H H N Answer the following questions using only the structures in the diagram. Each structure may be used once, more than once or not at all. Which structure, A, B, C, D or E, is a compound which is used as a fertiliser, is a diatomic molecule, contains chloride ions, is a gas which turns damp red litmus paper blue, is an element? Structure A is sulfur dioxide. Sulfur dioxide is an atmospheric pollutant. State one source of sulfur dioxide. Give one adverse effect of sulfur dioxide on health. An isotope of nitrogen is represented by the symbol 15N 7 . Deduce the number of protons, neutrons and electrons in this isotope of nitrogen. number of protons number of neutrons number of electrons
0620_w17_qp_33
THEORY
2017
Paper 3, Variant 3
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Lithium, sodium and potassium are GroupI elements. Name the type of bonding in these elements. Sodium reacts with cold water to form hydrogen gas and a solution of a strong alkali. State the test for hydrogen gas. test positive result  Suggest the pH of a solution of a strong alkali.  pH = Name a substance which can be used to confirm the pH of a solution of a strong alkali. Write the symbol equation for the reaction between sodium and cold water. Include state symbols. Lithium has two naturally occurring types of atoms, 6Li and 7Li. State the name given to atoms of the same element with different nucleon numbers. Complete Table2.1 to show the number of protons, neutrons and electrons in the atom and ion of lithium shown. Table2.1 6Li 7Li+ protons neutrons electrons  Table 2.2 shows the relative abundance of the two naturally occurring atoms of lithium. Table 2.2 atom 6Li 7Li relative abundance 10% 90% Calculate the relative atomic mass of lithium to one decimal place.  relative atomic mass = Potassiumoxide, K2O, is an ionic compound. Complete Fig.2.1 to show the electronic configurations of the ions in potassiumoxide. Show the charges on the ions. K O K  
0620_m23_qp_42
THEORY
2023
Paper 4, Variant 2
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Use Clean air contains a number of different gases. State the names of the two gases which make up most of the air. A sample of air is drawn through the apparatus shown below. white copper sulphate limewater air to suction pump heated copper When the air is drawn through the apparatus, the lime water turns milky. Which gas turns lime water milky? The white copper sulphate turns blue. State the name of the substance which turns white copper sulphate blue. Oxygen is removed from the air by passing it over heated copper. Complete the equation for this reaction. 2Cu + → CuO Examiner's Use Pure air contains about 1% argon. In which Period of the Periodic Table is argon? State the name of the Group of elements to which argon belongs. Draw the electronic structure of argon. Why is argon used in lamps? An isotope of argon has a mass number of 40. Calculate the number of neutrons in this isotope of argon. A small amount of xenon is present in the air. A few compounds of xenon have been made in recent years. Calculate the relative molecular mass of xenon difluoride, XeF2. Examiner's Use The structure of another compound of xenon is shown below. Xe F F F F O Write the simplest formula for this compound of xenon. Describe the type of bonding in this compound.
0620_s07_qp_2
THEORY
2007
Paper 2, Variant 0
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For Examiner's Use Caesium is a metal in Group I of the Periodic Table. State two physical properties of caesium. State the number of electrons in the outer shell of a caesium atom. An isotope of caesium has a mass number of 133. What do you understand by the term isotope? Calculate the number of neutrons in this isotope of caesium. Complete the following table to estimate the boiling point of caesium and predict the reactivity of caesium with water. Group I metal density / g / cm3 boiling point / °C reactivity with water sodium 0.97 fizzes quickly, disappears gradually and does not burst into flame potassium 0.86 fizzes very quickly, disappears quickly and bursts into flame with a little spitting rubidium 1.53 fizzes extremely quickly, bursts into flame then spits violently and may explode caesium 1.88 For Examiner's Use The diagram shows the structure of caesium chloride. Cs+ Cl – Cs+ Cl – Cs+ Cl – Cs+ Cl – Cs+ Cl – Cs+ Cl – Cs+ Cl – Cs+ Cl – Cs+ Cl – Use this diagram to work out the simplest formula for caesium chloride. Caesium chloride dissolves in water to form a neutral solution. State the pH of a neutral solution. Describe a test for chloride ions. test result
0620_w09_qp_2
THEORY
2009
Paper 2, Variant 0
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Both strontium and sulfur have chlorides of the type XCl 2. The table below compares some of their properties. strontium chloride sulfur chloride appearance white crystals red liquid formula SrCl 2 SCl 2 melting point / °C –120 boiling point / °C conductivity of liquid good poor solubility in water dissolves to form a neutral solution reacts to form a solution of pH 1 Use the data in the table to explain why sulfur chloride is a liquid at room temperature, 25 °C. Strontium is a metal and sulfur is a non-metal. Explain why both have chlorides of the type XCl 2. The electron distribution of a strontium atom is 2 + 8 + 18 + 8 + 2. Deduce the name of the acidic compound formed when sulfur chloride reacts with water. Explain the difference in the electrical conductivity of liquid strontium chloride and liquid sulfur chloride. Strontium chloride-6-water can be made from the insoluble compound, strontium carbonate, by the following reactions. SrCO3+ 2HCl → SrCl 2+ CO2+ H2OSrCl 2 + 6H2O→ SrCl 2.6H2OThe following method was used to prepare the crystals. Add excess strontium carbonate to hot hydrochloric acid. Filter the resulting mixture. Partially evaporate the filtrate and allow to cool. Filter off the crystals of SrCl 2.6H2O. Dry the crystals between filter papers. How would you know when excess strontium carbonate had been added in step 1? Why is it necessary to fi lter the mixture in step 2? In step 3, why partially evaporate the fi ltrate rather than evaporate to dryness? In the above experiment, 50.0 cm3 of hydrochloric acid of concentration 2.0 mol / dm3 was used. 6.4 g of SrCl 2.6H2O was made. Calculate the percentage yield. number of moles of HCl used = number of moles of SrCl 2.6H2O which could be formed = mass of one mole of SrCl 2.6H2O is 267 g theoretical yield of SrCl 2.6H2O = g percentage yield = %
0620_w12_qp_31
THEORY
2012
Paper 3, Variant 1
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