Answer:
Q1: 320 J.
Q2: The 150 g Al will reach a higher temperature.
Explanation:
<u><em>Q1:</em></u>
- The amount of heat added to or released from a substance (Q) can be calculated from the relation:
<em>Q = m.c.ΔT.</em>
where, Q is the amount of heat added or released,
m is the mass of the substance (m = 40.0 g),
c is the specific heat of the substance (c = 0.5 J/g.°C, the value of c of the solid ethanol, ethanol be solid at the temperature change mentioned).
ΔT is the temperature difference (final T - initial T) (ΔT = − 136 °C − (− 120 °C) = − 16 °C.
∴ Q = m.c.ΔT = (40.0 g)(0.5 J/g.°C)(− 16 °C) = − 320 J.
The negative sign means that the heat is released.
<em>∴ The amount of heat is released when 40.0 g of ethanol cools from (−120 °C to −136 °C) = 320 J.</em>
<em>Q2:</em>
Explanation:
- The amount of heat added to a substance (Q) can be calculated from the relation:
<em>Q = m.c.ΔT.</em>
where, Q is the amount of heat added,
m is the mass of the substance,
c is the specific heat of the substance,
ΔT is the temperature difference (final T - initial T).
Since, Q and c is constant, ΔT will depend only on the mass of the substance (m).
∵ ΔT is inversely proportional to the mass of the substance.
∴ The piece with the lowest mass (150.0 g) will reach a higher temperature than that of a higher mass (250.0 g).
<em>So, the right choice is: The 150 g Al will reach a higher temperature.</em>
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