calorimeter

mix initial

= calorimeter

• C
  TT

q

^h

qcalorimeter= −qwater

qwater= (mass water) ⋅(specific heat) ⋅(Tmix−Tavg)

At 23.0°C: 50 0. mL H O 1 2 #:0 983..gmL-^1 =49 9gHO 2

At 61.0°C: 50 0. mL H 1 20 #:0 983..gmL-^1 =49 1gHO 2

Total mass = 49.9 g + 49.1 g = 99.0 g H 2 O

= (99. 0 g) ⋅(4.18 J / g ⋅°C) ⋅(41.4 °C −42.0 °C)

= −2.5 × 102 J (extra significant figure carried)

Heat gained by calorimeter = −qwater= 2.5 × 102 J (extra significant figure carried)

.

.

CC.

J JC

41 4

25 10 14

23 0

calorimeter

mix initial

= calorimeter #^2 :^1

• ==
  % - %
  C % -
  TT

q

^ h ` j

2. In the same fashion, graphs were constructed of the temperature changes for each of the
   three reactions. A summary of the information is presented in the table below. Calculate
   the heat evolved in each reaction (kJ/mol of product). Assume the density of each solution

= 1.00 g ⋅mL–1.

Tinitial(°C) Tat mixing(°C)

HCl + NaOH 23.0 35.6

NH 4 Cl + NaOH 22.9 24.1

NH 3 + HCl 23.0 33.1

(a) HCl + NaOH

[]

volume molarity

mass specific heat ∆∆T C T

'

''' '

rxn sol n

sol n sol n sol n calorimeter sol n

#

###

=

-+

q

^ h _ i ^^hh

../

.../.

0 500 2 0

100 4 18 3 56 23 0 14 12 5

L mole L

gsol n' J/g C C C J C C

#

#:##

=

: %%%%%``-+jjD

../

. /
0 0500 2 0

54 10 54

L mol L

(^3) J kJ mol

= - # =-
(b) NH 4 Cl + NaOH
[]
volume molarity
mass specific heat ∆∆T C T
'
''' '
rxn sol n
sol n sol n sol n calorimeter sol n

=
-+
q
^ h _ i ^^hh
../
.....
0 0500 2 0
100 4 18 24 1 22 9 14 1 2
L mol L
gsol n' J/g C C C J/g C C

#:#:#

--+: %%%%%``jjD
../

. ./
0 0500 2 0

52 10 52

L mol L

(^2) J kJ mol

= - # =-
Part III: AP Chemistry Laboratory Experiments