Question

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texas chemistry teks 13a - 13d exam

1. which statement best illustrates the first law of thermodynamics as described in teks 13a?

a. heat will spontaneously flow from a colder body to a warmer body.
b. energy cannot be created or destroyed, only converted from one form to another.
c. a system at absolute zero has no entropy.
d. when two systems are each in equilibrium with a third, they are in equilibrium with each other.

1. which of the following everyday examples best illustrates the second law of thermodynamics (teks 13a)?

a. a hot cup of coffee left in a room eventually cools to room temperature.
b. ice forms spontaneously in a warm room.
c. a billiard ball rolling across a table loses speed due to friction.
d. a battery converts chemical energy into electrical energy without loss.

1. the standard states (teks 13b) that students should \investigate the process of heat transfer using calorimetry.\ which experiment would most directly address this expectation?

a. measuring the volume of a gas at constant temperature.
b. mixing a hot acid and a base, measuring the temperature change of water.
c. using a spectrophotometer to measure absorbance of a dye solution.
d. observing the decay of a radioactive isotope over time.

1. in a calorimetry experiment, 50 g of water at 22.0°c receives 4200 j of heat energy. what is the final temperature of the water? (assume specific heat of water = 4.20 j/g°c)

a. 38.0°c
b. 42.0°c
c. 22.8°c
d. 42.5°c

Explanation:

Step1: Use the heat formula

The formula for heat \(Q = mc\Delta T\), where \(Q\) is heat energy, \(m\) is mass, \(c\) is specific heat capacity, and \(\Delta T=T_{final}-T_{initial}\).
We know \(Q = 4200\space J\), \(m = 50\space g\), \(c=4.20\space J/g^{\circ}C\), \(T_{initial}=22.0^{\circ}C\).
Substitute into the formula: \(4200=50\times4.20\times(T_{final} - 22.0)\)

Step2: Solve for \(\Delta T\)

First, simplify the right - hand side: \(50\times4.20 = 210\).
The equation becomes \(4200=210\times(T_{final}- 22.0)\).
Then, \(\frac{4200}{210}=T_{final}-22.0\).
\(20=T_{final}-22.0\)

Step3: Solve for \(T_{final}\)

\(T_{final}=20 + 22.0=42.0^{\circ}C\)

Answer:

B. \(42.0^{\circ}C\)