4.1. The gaseous state: ideal and real gases and \( pV = nRT \)
A subsection of Chemistry, 9701, through 4. States of matter
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Trihalomethanes are organic molecules in which three of the hydrogen atoms of methane are replaced by halogen atoms, for example CHF3. The equation shows a reaction to produce CHF3. CHI3+ 3AgFCHF3+ 3AgIUse the data to calculate the enthalpy change of reaction, ΔHr , for this formation of CHF3. compound enthalpy change of formation, ΔHf / kJ mol–1 CHI3–182.1 CHF3– 692.9 AgF–204.6 AgI– 61.8  enthalpy change of reaction, ΔHr = kJ mol–1 The graph shows the relationship between pV and p at a given temperature for CHF3 and an ideal gas. pV p / atm CHF3 ideal gas CHF3 is not an ideal gas. State three basic assumptions that scientists make about the properties of ideal gases.  Explain why CHF3 deviates from the properties of an ideal gas at pressures greater than 300 atm. A different trihalomethane, CHCl 3, reacts with O2 to produce carbonyldichloride. HCl is also released as a product of this reaction. C carbonyl dichloride Cl Cl O Write an equation for this reaction of CHCl 3 with O2. The conversion of CHCl 3 to carbonyldichloride can be monitored by infra-red spectroscopy. The infra-red spectrum of carbonyldichloride is shown. transmittance wavenumber / cm–1 On the infra-red spectrum of carbonyldichloride identify with an X the absorption that would not be present in an infra-red spectrum of CHCl 3. Explain your answer.  Suggest another difference between the infra-red spectra of CHCl 3 and carbonyldichloride. 
9701_w18_qp_22
THEORY
2018
Paper 2, Variant 2
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