12. Experimental techniques and chemical analysis
A section of Chemistry, 0620
Listing 10 of 677 questions
A student set up the apparatus shown below. The concentrated hydrochloric acid gives off hydrogen chloride gas. After 15 seconds, the damp blue litmus paper begins to turn red. After 25 seconds, the litmus paper has turned completely red. damp blue litmus paper cotton wool soaked in concentrated hydrochloric acid long glass tube at the start slightly red after 15 seconds all red after 25 seconds Use ideas about moving particles to explain these observations. Hydrogen chloride reacts with ammonia to form a salt which has the formula NH4Cl. State the name of this salt. Hydrochloric acid reacts with iron to form iron(chloride and hydrogen. Write a word equation for this reaction. Describe a test for iron(ions. test result A student investigates various methods of protecting iron from rusting. She sets up four tubes as shown in the diagram below. tube 1 iron nail water iron tube 2 tube 3 tube 4 oil iron water iron completely coated with plastic water iron incompletely coated with plastic Tube 1 contains unprotected iron. What is the purpose of this experiment? State the names of the two substances needed for iron to rust. and Explain why the iron in tube 4 does not rust. Explain why the iron in tube 3 eventually rusts.
0620_s13_qp_21
THEORY
2013
Paper 2, Variant 1
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Concentrated ammonia solution gives off ammonia gas. Concentrated hydrochloric acid gives off hydrogen chloride gas. Ammonia, NH3, and hydrogen chloride, HCl, are both colourless gases. Ammonia reacts with hydrogen chloride to make the white solid ammonium chloride. Apparatus is set up as shown. cotton wool soaked in concentrated hydrochloric acid cotton wool soaked in concentrated ammonia solution glass tube A B C D After ten minutes a white solid forms in the tube where the gases meet. Write the chemical equation for the reaction of ammonia with hydrogen chloride. Name the process by which the ammonia and hydrogen chloride gases move in the tube. At which point, A, B, C or D, does the white solid form? Explain why the white solid forms at that point. the solid forms at explanation The experiment was repeated at a higher temperature. Predict how the results of the experiment would be different. Explain your answer. Some of the white solid is removed from the tube and dissolved in water. Describe how the white solid could be tested to show it contains, ammonium ions, test result chloride ions. test result The diagram shows the electron arrangement in a molecule of ammonia, showing only outer shell electrons. N H H H State the type of bonding in ammonia. Hydrazine, N2H4, is another compound of nitrogen and hydrogen. Complete the diagram to show the electron arrangement in a molecule of hydrazine, showing only outer shell electrons. N N H H H H Nylon and proteins are both polymers containing nitrogen. Name the linkages found in the polymers of nylon and protein. Describe one difference in the structures of nylon and protein. What is the general name given to the products of hydrolysis of proteins? Suggest the structure of the monomer used to make the polymer shown. N H C O n
0620_s16_qp_43
THEORY
2016
Paper 4, Variant 3
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Sodium is in Group I of the Periodic Table. Describe two physical properties of sodium which are different from the physical properties of transition elements such as copper.  Sodium reacts rapidly with water. Give one observation made when sodium is added to water. Some car airbags contain sodium azide. When a car airbag is used the sodium azide, NaN3, decomposes. The products are nitrogen and sodium. The equation for the decomposition of sodium azide is shown. 2NaN32Na+ 3N2Calculate the mass, in g, of sodium azide needed to produce 144 dm3 of nitrogen using the following steps. ● ● Calculate the number of moles in 144 dm3 of N2 measured at room temperature and pressure.  moles of N2 = mol ● ● Determine the number of moles of NaN3 needed to produce this number of moles of N2.  moles of NaN3 = mol ● ● Calculate the relative formula mass, Mr, of NaN3.  Mr = ● ● Calculate the mass of NaN3 needed to produce 144 dm3 of N2.  g  Some airbags contain silicon(oxide. When the airbag is used sodium oxide is formed. Oxides can be classified as acidic, amphoteric, basic or neutral. Classify each of these oxides: sodium oxide silicon(oxide.  Lead(azide is insoluble in water. Solid lead(azide can be made in a precipitation reaction between aqueous lead(nitrate and aqueous sodium azide. Lead(azide has the formula Pb(N3)2. Deduce the formula of the azide ion. Complete the chemical equation for the reaction between aqueous lead(nitrate and aqueous sodiumazide to form solid lead(azide and aqueous sodiumnitrate. Include state symbols. Pb(NO3)2+ NaN3Pb(N3)2( ) + ( )  Describe how you could obtain a sample of lead(azide that is not contaminated with any soluble salts from the reaction mixture. An organic compound made from sodiumazide has the composition by mass: 49.5%carbon, 7.2%hydrogen and 43.3%nitrogen. Calculate the empirical formula of the organic compound.  
0620_s19_qp_43
THEORY
2019
Paper 4, Variant 3
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Questions Discovered
677