11.2. The chemical properties of the halogen elements and the hydrogen halides
A subsection of Chemistry, 9701, through 11. Group 17
Listing 10 of 102 questions
Magnesium silicide, Mg2Si, is a compound made by heating magnesium with sand. Draw a ‘dot-and-cross’ diagram to show the arrangement of outer electrons present in a formula unit of Mg2Si. Assume magnesium silicide is an ionic compound.  When solid Mg2Si is added to water, silane gas, SiH4, and a solution of magnesiumhydroxide are produced. Construct the equation for this reaction. Include state symbols. Suggest, with reference to structure and bonding, why SiH4 is a gas at room temperature. The table shows the electronegativity values of carbon, hydrogen and silicon. element carbon hydrogen silicon electronegativity 2.5 2.1 1.8 C–H and Si–H bonds have weak dipoles. Use the electronegativity values in the table to show the polarity of the C–H and Si–H bonds. C––H Si––H  Explain why methane, CH4, has no overall dipole moment. SiH4 reacts in air without heating but CH4 must be ignited before combustion occurs. SiH4 + 2O2 SiO2 + 2H2O CH4 + 2O2 CO2 + 2H2O Suggest, with reference to bond energies from the Data Booklet, why SiH4 reacts in air without heating but CH4 must be ignited. Silicon dioxide reacts with hot, concentrated sodium hydroxide. Identify the two products formed during this reaction. Describe the behaviour of the silicon dioxide during this reaction. 
9701_s19_qp_21
THEORY
2019
Paper 2, Variant 1
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Gallium is a metal in Group13 of the PeriodicTable. There are two stable isotopes of gallium, 69Ga and 71Ga. State, with reference to subatomic particles, how the isotopes 69Ga and 71Ga differ from each other. State what further information is needed to calculate the relative atomic mass of gallium. Gallium and its compounds show similar properties to aluminium and its compounds. Gallium reacts with excess chlorine to form gallium trichloride. At 500 °C, galliumtrichloride is a gas. Suggest the type of attraction that exists at 500 °C ● ● between atoms within a gallium trichloride molecule ● ● between gallium trichloride molecules.  When galliumtrichloride is cooled a solid, Ga2Cl 6, forms. Suggest the name of the attraction formed between two galliumtrichloride molecules to form Ga2Cl 6. Gallium metal reacts rapidly when exposed to air. A white solid layer is formed on its surface. Suggest an equation to describe the reaction occurring when gallium metal is exposed to air. The table gives the formula of each gallium-containing product formed when galliumoxide reacts separately with hot aqueous hydrochloricacid and hot aqueous sodiumhydroxide. formula of gallium-containing product hot aqueous hydrochloric acid GaCl 3 hot aqueous sodium hydroxide NaGa(OH)4 Give the name of the type of behaviour shown by galliumoxide in these reactions. 
9701_s20_qp_21
THEORY
2020
Paper 2, Variant 1
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The elements in Group17 are known as the halogens. Between the molecules of Group 17 elements van der Waals’ forces exist. State the trend in the relative strength of van der Waals’ forces down Group 17. State the physical state of each of the halogens under room conditions. chlorine bromine iodine  A solution of aqueous bromide ions, Br –, is added to separate samples of Cl 2and I2. Describe what is observed in each reaction. Explain your answer in terms of the relative reactivity of these elements as oxidising agents. observation on addition to Cl 2observation on addition to I2explanation  Bleach is made by reacting Cl 2 with cold NaOH. Write an equation for the reaction of Cl 2 with cold NaOH. When Cl O–is added to water, it behaves as a Brønsted-Lowry base. Define the term Brønsted-Lowry base. Write an ionic equation for the reaction between Cl O– and H2O. The concentration of NaCl O in bleach S is x g dm–3. NaCl O reacts with H2O2as shown. H2O2+ NaCl O→ H2O+ NaCl + O2A 5.00 cm3 sample of S completely reacts with H2O2. The volume of O2produced is 24.0 cm3 under room conditions. Assume that only the NaCl O in S reacts with H2O2. Calculate x. Show your working.  x = g dm–3  Sodium chlorate(, NaCl O, oxidises dilute hydrochloric acid to form three products. The products which contain chlorine have chlorine species with oxidation number –1 or 0. No other species changes its oxidation number during the reaction. Use this information to complete the ionic equation. Cl O– + HCl → + +  
9701_s21_qp_23
THEORY
2021
Paper 2, Variant 3
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Hydrogeniodideisaddedtoanevacuatedreactionvessel.Thevesselissealedandwarmed.A decompositionreactionoccurs.Hydrogenandiodineareformed.Somehydrogeniodideremains. Whenequilibriumisestablished,thetotalpressureis1.20s105Pa.Thepartialpressureofhydrogen is4.00s103Pa. Hydrogeniodide,hydrogenandiodineareallgaseousundertheconditionsused. WhatisthevalueofKpfortheequilibriumatthistemperature,assumingthedecompositionisthe forwardreaction?
9701_s23_qp_12
MCQ
2023
Paper 1, Variant 2
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