Answer:
Final T = 64.0°C.
Explanation:
Q = m.c.ΔT.
where, Q is the amount of heat absorbed by Na (Q = 1840 J),
m is the mass of Na (m = 68.0 g),
c is the specific heat capacity of Na (c = 1.23 J/g °C),
ΔT is the temperature difference (final T - initial T) (ΔT = final T - 42.0°C).
∵ Q = m.c.ΔT.
∴ (1840 J) = (68.0 g)(1.23 J/g °C)(final T - 42.0°C)
(final T - 42.0°C) = (1840 J)/(68.0 g)(1.23 J/g °C) = 22.0°C.
∴ final T = 22.0°C + 42.0°C = 64.0°C.