Q_w = 307.3 J
C_m = .233 J/g•K
%error = 39.95%
For simplicity's sake, I'm relabeling
Q_w as Q1
m_w as m1
C_w as c1
T_eq as T2
T_w as T1
Q_m as Q2
m_m as m2
C_m as c2
experimental value as exp
actual value as actual
Question 1
Q1 = m1•c1•(T2-T1)
Identify what you know
m1 = 124g
c1 = 4.13 J/g • K
T2 = Final temperature = 22.3°C
T1 = Initial temperature = 21.7°C
Convert Celsius to Kelvin (C+273.15=K)
T2 = 295.45 K
T1 = 294.85 K
Plug in
Q1 = 124g•(4.13 J/g•K)•(295.45K - 294.85K)
Solve
Q1 ≈ 307.3 J
Question 2
-Q1 = Q2 = m2•(c2)•(T2-100)
Ignore Q2 for a second, and you're left with
-Q1 = m2•(c2)•(T2-100)
which is the same thing.
Identify what you know
Q1 = 307.3 J
m2 = 17g
T2 = 22.3°C
Plug in
-(307.3J) = 17g • c2 • (22.3°C-100°C)
Solve
-307.3 J = (-1320.9 g•°C) • c2
c2 = .233 J/g•°C or J/g•K (I'll explain later)
Question 3
%err = ((exp - actual)/actual) • 100%
Identify what you know
exp = .233 J/g•K
actual = .388 J/g•K
Plug in
%err = ((.233 J/g•K - .388 J/g•K)/ .388 J/g•K) • 100%
Solve
%err = -39.95 %
Take the absolute value
%err = 39.95%
Referring to earlier change in units:
The reason we can not use the K value of T2 (295.45K) is because the formula provided (T2-100) does not account for T2 being in K. It only accounts for T2 being in °C.