A mixture of gases A2 and B2 are introduced to a slender metal cylinder that has one end closed and the other fitted with a pist

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A mixture of gases A2 and B2 are introduced to a slender metal cylinder that has one end closed and the other fitted with a pist

on that makes a gas-tight seal so that the gases are a closed system. The cylinder is submerged in a large beaker of water whose temperature is 25∘C, and a spark is used to trigger a reaction in the cylinder. At the completion of the reaction, the piston has moved downward, and the temperature of the water bath has increased to 28∘C. If we define the system as the gases inside the cylinder, which of the following best describes the signs of q, w, and ΔE for this reaction?
(a) q < 0, w < 0, ΔE < 0
(b) q < 0, w > 0, ΔE < 0
(c) q < 0, w > 0, the sign of ΔE cannot be determined from the information given
(d) q > 0, w > 0, ΔE > 0
(e) q > 0, w < 0, the sign of ΔE cannot be determined from the information given

Chemistry

1 answer:

eduard [2.6K] · Answer 1 · 2026-04-06T17:19:00+03:00

Response:

q < 0, w > 0, the sign of ΔE cannot be ascertained from the provided details

Explanation:

Assessing the sign of q

The water bath's temperature before the reaction is at 25 °C

Following the reaction, the water bath's temperature rises to 28 °C, suggesting that heat was released from the system during the reaction.

If heat is absorbed by the system, q is positive; if heat is released, q is negative, leading to the conclusion that q < 0 in this scenario.

Determining the sign of w

The downward movement of the piston indicates a reduction in the system's volume, meaning work was conducted on the system. When work is done on the system, w is considered positive; hence, w > 0 in this case.

Evaluating ΔE sign

According to the first law of thermodynamics, the relationship among ΔE, q, and w is represented as follows:

ΔE = q + w

In this instance, since q is negative and w is positive, the resulting sign of ΔE is determined by the relative magnitudes of q and w. Since we lack sufficient information to gauge these magnitudes, we cannot definitively determine the sign of ΔE based on the given data.

As a result, the correct option among the choices presented is c: q < 0, w > 0, the sign of ΔE cannot be discerned from the information given.