chem jan 22 2014 revision of c and q, delta...
TRANSCRIPT
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chem jan 22 2014 revision of c and Q, delta H
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Jan 225:26 PM
With a partner or small group, talk about the different specific heat capacities of each substance in the above list.
a) What is the link between the value of specific heat capacity and energy?b) Is energy absorbed during an increase or decrease of temperature?c) Which one would release /absorb the biggest amount of energy when its temperature is decreased/increased? Why?d) Which one would release/absorb the least amount of energy when its temperature is decreased/increased? Why?
Jan 225:54 PM
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chem jan 22 2014 revision of c and Q, delta H
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Jan 225:58 PM
Examine the following incorrect statement:
The following are the possible corrections for the statement above:
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chem jan 22 2014 revision of c and Q, delta H
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chem jan 22 2014 revision of c and Q, delta H
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chem jan 22 2014 revision of c and Q, delta H
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chem jan 22 2014 revision of c and Q, delta H
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chem jan 22 2014 revision of c and Q, delta H
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chem jan 22 2014 revision of c and Q, delta H
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Jan 229:02 PM
5a) We have to find delta H for each solution:Solution 1 : Sodium hydroxide (NaOH)
QH2O= (mass of water)(c of water)(deltaT of water)
= (100)(4.184)(28.422.3)
= (100) (4.184) (6.1)
= 2552.24J
Qrxn = 2552.24J
delta H = (Qrxn) (Molar mass of reactant)
mass of reactant
= (2552.24)(39.997)
0.56
delta H = 182289.18J/mol
exothermic reaction
Molar mass of NaOH:
Na = 22.99
O = 15.999
H = 1.008
Total NaOH= 39.997g/mol
Jan 234:29 PM
5b) We have to find delta H for each solution:Solution 2 : Ammonium Nitrate (NH4NO3)
QH2O= (mass of water)(c of water)(deltaT of water)
= (50.5)(4.184)(13.825)
= (50.5) (4.184) (11.2)
= 2366.4704J
Qrxn = 2366.4704J
delta H = (Qrxn) (Molar mass of reactant)
mass of reactant
= (2366.4704)(80.043)
6.75
delta H = 28062.13J/mol
endothermic reaction
Molar mass of NH4NO3:
2 N = 2 x 14.007 = 28.014
3 O = 3 x 15.999 = 47.997
4 H = 4 x 1.008 = 4.032
Total NH4NO3= 80.043g/mol
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chem jan 22 2014 revision of c and Q, delta H
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Jan 234:41 PM
5c) We have to find delta H for each solution:Solution 3 : Hydrochloric acid (HCl)
QH2O= (mass of water)(c of water)(deltaT of water)
= (150)(4.184)(43.624.7)
= (150) (4.184) (18.9)
= 11861.64J
Qrxn = 11861.64J
delta H = (Qrxn) (Molar mass of reactant)
mass of reactant
= (11861.64)(36.461)
2.05
delta H = 210969.39J/mol
exothermic reaction
Molar mass of HCl:
H = 1.008
Cl = 35.453
Total HCl = 36.461g/mol
Jan 234:52 PM
6) Molar heat or delta H = ?
2.5g of MgCl2
250mL of water
T1= 22.8C
T2= 12.5C
QH2O= (mass of water)(c of water)(deltaT of water)
= (250)(4.184)(12.522.8)
= (250) (4.184) (10.3)
= 10773.8J
Qrxn = 10773.8J
delta H = (Qrxn) (Molar mass of reactant)
mass of reactant
= (10773.8)(119.516)
2.5
delta H = 515056.59J/mol
endothermic reaction
Molar mass of MgCl2:Mg = 2 x 24.305 = 48.61
2 Cl = 2 x 35.453 = 70.906
Total MgCl2= 119.516g/mol
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