11. Group 17
A section of Chemistry, 9701
Listing 10 of 617 questions
The halogens and their compounds have a wide variety of uses and the chemical and physical properties of the elements show regular patterns related to their positions in Group VII. Chlorine, bromine and iodine all react with hydrogen. State the trend in the reactivities of the halogens with hydrogen. Explain this trend in terms of bond energies. In the laboratory it is not very convenient to prepare hydrogen halides from their elements. Hydrogen halides can be prepared from their salts. Write an equation for the reaction of calcium chloride, CaCl 2, with concentrated sulfuric acid. Explain why hydrogen iodide is not prepared in this way. When potassium bromide, KBr, reacts with concentrated sulfuric acid, sulfur dioxide, SO2, is produced. State what you would see and write an equation for this reaction. Give the structures of the four structural isomers of C4H9Br and identify each as primary, secondary or tertiary. Name the isomer of C4H9Br that contains a chiral centre and draw the three-dimensional structures of the two optical isomers. name structures Aqueous silver nitrate solution was added to separate tubes containing chloroethane, bromoethane and iodoethane. The tubes were heated in a water bath. A yellow precipitate appeared fi rst in the tube containing iodoethane, followed by a cream precipitate in the tube containing bromoethane and fi nally a white precipitate appeared in the tube containing chloroethane. Explain these observations. Give the full name of the mechanism for the reaction between aqueous sodium hydroxide and bromoethane. Complete the diagram below to represent this mechanism. Include all necessary curly arrows, partial charges and lone pairs. C H Br H H C H HO– H C H OH + Br – H H C H H In the past, CFCs such as CF3Cl were widely used as refrigerants. State a property of CFCs which makes them suitable for use as refrigerants. State the damaging effect of CFCs in the upper atmosphere. Explain your answer.
9701_s14_qp_23
THEORY
2014
Paper 2, Variant 3
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Describe and explain how the boiling points of the tetrachlorides of the Group IV elements vary down the group. The tetrachlorides are all covalent compounds. Draw a diagram showing the shape of a molecule of silicon tetrachloride, including values for bond angles. The noble gas xenon forms a tetrafluoride, XeF4. Only four of xenon’s outer shell electrons are used in bonding to the fluorine atoms. Draw a dot-and-cross diagram showing how the outer-shell electrons are arranged in XeF4. Predict the shape and the bond angles in XeF4. Describe and explain how the reactions of CCl4 and SiCl4 with water differ. Write an equation for any reaction that occurs. Use [T Many tonnes of lead tetrachloride used to be produced to make the anti-knock petrol additive tetraethyl-lead, Pb(C2H5)4, by the following reaction. PbCl4 + ………… Na + ………… C2H5Cl ⎯⎯→ Pb(C2H5)4 + ………… NaCl Balance this equation and use it to calculate the mass of sodium needed to produce 1.0 kg of tetraethyl-lead.
9701_w06_qp_4
THEORY
2006
Paper 4, Variant 0
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What is meant by the term bond energy? Describe and explain what is observed when a red-hot wire is plunged into separate samples of the gaseous hydrogen halides HCl and HI. How are bond energy values useful in interpreting these observations? The following reaction occurs in the gas phase. 3F2+ Cl22ClF3, ∆H o— r = –328 kJ mol–1 Use these and other data from the Data Booklet to calculate the average bond energy of the Cl-F bond in Cl F3.
9701_w09_qp_42
THEORY
2009
Paper 4, Variant 2
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Questions Discovered
617