PlanningEnergetics

Standard enthalpy change of neutralisation0 Definition0 Dependent variable0 Independent variable0 Value of Hneut

o

0 Basicity of acids

Typical Experimental Set-up

For each set of data

Amt. of HCl

Amt. of NaOH

Initial temp. of HCl

Initial temp.of NaOH

Ave. initial temp.

Typical Table of Data

Amt. HnX Amt. NaOH

Max. temp.

T = Tmax - Tinitial

50 1040 2030 3020 4010 50

For example, using 1 mol dm-3 acid and NaOH

HnX + nNaOH NanX + nH2O

Better than the word “Final”

Typical Graph – type 1

Vol. of NaOH used / cm3

10 2030

40 50

If Basicity of acid, n = 1

Amt. HnX Amt. NaOH

Max. temp.

T = Tmax - Tinitial

50 1040 2030 3020 4010 50

Work out using HClAmt. HCl Amt.

NaOHHneut

o

50 10 - 60 x c x T1

0.0140 20 - 60 x c x T2

0.0230 30 - 60 x c x T3

0.0320 40 - 60 x c x T2

0.0210 50 - 60 x c x T1

0.01

Typical Graph – type 2

Vol. of NaOH used / cm3

10 2030

40 50

Type 1

Type 2

If Basicity of acid, n = 2

Amt. HnX Amt. NaOH

Max. temp.

T = Tmax - Tinitial

50 1040 2030 3020 4010 50

Work out using H2SO4

Amt. H2SO4

Amt. NaOH

Hneuto

50 10 - 60 x c x T1

0.0140 20 - 60 x c x T2

0.0230 30 - 60 x c x T3

0.0320 40 - 60 x c x T4

0.0410 50 - 60 x c x T2

0.02

Most informative region

Vol. of NaOH used / cm3

10 2030

40 50

Type 1

Type 2

Monobasic

Dibasic

Considerations for accuracy and

reliability0 Insulation – styrofoam cup, lid0 Stability of set-up – beaker0 thermometer – precision0 Consistency of stirring

Standard enthalpy change of combustion

0 Definition0 Dependent variable0 Independent variable

Typical Experimental Set-up

Typical Table of Data

For example,CnH2n+2O + O2 nCO2 + (n+1)H2O

Initial mass of spirit

lamp

Final mass of spirit

lamp

Initial temp

Max. temp.

Raw Data

Work out using C2H5OH

Mass of C2H5OH

T Hcombustiomo

- mH2O x c x TnC2H5OH

Processed Data

Refer to HCI/2010 for consideration on heat absorbed by Cu can.

Considerations for accuracy and

reliability0 Heat loss to surroundings –

insulation of Cu can0 Heat loss to Cu can – consider

heat capacity of Cu can0 Incomplete combustion of alcohol

If diff alcohols are used

Standard enthalpy change of reaction

0 Definition0 Dependent variable0 Independent variable

Na2CO3(s) + 2HCl(aq) 2NaCl(aq) + H2O(l) + CO2(g)

Suitable quantities of reactants to use: 0.010 mol Na2CO3 (1.06 g Na2CO3)

0.020 mol HCl ( 20 cm3 1 mol dm-3 HCl)

Mass of empty weighing bottle =

Mass of weighing bottle and Na2CO3=

Mass of emptied weighing bottle and residue

=

Volume of HCl used =

Initial temp of HCl =

Typical Experimental Set-up

Table of dataTime / min Temperature /

oC012

3.54567

Typical graph

Temp / oC

Time / min1 23.5

4 5 6 7

23.5

Temp / oC

Time / min

T

At 3 min, time of addition of Na2CO3

Calculate Hreactiono

Hreactiono = - MHCl x c x T

nNa2CO3

Assume density of HCl = 1 g cm-3

Na2CO3(s) + 2HCl(aq) 2NaCl(aq) + H2O(l) + CO2(g)

NaHCO3(s) + HCl(aq) NaCl(aq) + CO2(g) + H2O(l)

T

Calculate Hreactiono

Hreactiono = + MHCl x c x T

nNaHCO3

Assume density of HCl = 1 g cm-3

NaHCO3(s) + HCl(aq) NaCl(aq) + H2O(l) + CO2(g)

Think about…

0 The standard enthalpy change of:

Na2CO3(s) + HCl(aq) NaHCO3(aq) + NaCl(aq)