An isoperibol solution reaction calorimeter has been constructed. The precision and accuracy of the calorimeter were checked by measuring the enthalpy of reaction of tris(hydroxymethyl)aminomethane, THAM, in:(a) excess 0.1 mol dm - aqueous hydrochloric acid(b) excess 0.05 mol dm -3 aqueous sodium hydroxide. The mean of 8 runs were: (a) DeltaH298 (1296 <n< 1780) = -29.87 0.05 kj mol-1. Literature: DeltaH298 = -29.790 + 0.031 kj mol-1, n=1345. (b) DeltaH298 (1241 <n< 1550) = +17.18 +/- 0.05 kJ mol-1. Literature: DeltaH298 = +17.177 - 0 . 0 2 3 kj mol-1.(n is the mole ratio of water to THAM.) From measurement of the enthalpy of hydrolysis the standard enthalpy of formation of rubidium tetrafluoroiodate has been derived: DeltaH0F(RbIF4, c)298= -1121.51 + 6.33 kj mol -1. Heat capacity measurements for RblF4 over the range 273-303 K are also reported. The standard enthalpies of formation of some alkali metal polyhalides have been derived from calorimetric measurements, in the isoperibol mode, of the enthalpy of reaction of the crystalline polyhalides with: excess aqueous silver nitrate (ii) excess aqueous sulphur dioxide. The following standard enthalpies of formation at 298.15 K are reported: DeltaH°f (CsICl2,c) = -512.01 + 4.14 kJ mol-1; DeltaH°f (RbICl2,c) = -492.31 + 4.12 kJ mol-1; DeltaH°f (CsIBr2,c) = -446.32 + 4.08 kJ mol-1; DeltaH°f (RbIBr2,c) = -429.11 + 4.22 kJ mol-1; DeltaH°f (Csl3,c) = -359.79 - 5 .77 kJ mol-1; DeltaH°f (CsICl4,c) = -571.91 + 6.90 kJ mol-1 and DeltaH°f (RbICl4,c) =-554.36 i 6.99 kJ mol-1. (ii) DeltaH°f (CsICl2,c) = -530.35 + 0.67 kJ mol-1; DeltaH°f (RbICl2,c) = -461.36 + 1.40 kJ mol-1 and DeltaH°f (Csl3,c) = -381.96 +/- 1 .05 kJ mol-1. The standard enthalpy of formation in (i) for Csl3 is in good agreement with literature values derived from e.m.f. studies and from dissociation pressure measurements. The standard enthalpy of formation of AglO3(c) and the enthalpy change for the process [formula] were also derived from calorimetric measurements to supplement the ancillary data required to calculate the standard enthalpies of formation listed above. 'Thermochemical radii' of the ions IC12, IBr2-,IC14- and I3- have been calculated by the Kapustinskii-Yatsimirskii procedure in order to estimate lattice energies of the salts listed in (i) and DeltaH°f (lXn-,g) (where Xn = Cl2,Br2,Cl4 and I2). Additional lattice energies, standard enthalpies of formation and enthalpies of decomposition of other alkali-metal and alkaline-earth salts containing these ions are reported. 'Thermo chemical radii' of the ions Cl-,Br-,-~, N03-,S0₄2-,C103-,Br03- and I0 3 have been calculated to investigate the relationshipbetween the 'thermochemical radius' and the geometric size of an ion of given symmetry. Lattice energies of alkali-metal and alkaline-earth salts containing these ions have been estimated and compared with literature values.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:468508 |
| Date | January 1976 |
| Creators | Peake, Stuart John |
| Publisher | Royal Holloway, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://repository.royalholloway.ac.uk/items/b0ea98e2-d159-44f4-90d2-cbb3cbd2be71/1/ |
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