Question

At room temperature, solid iodine is in equilibrium with its vapor through sublimation and deposition. Describe how you would use radioactive iodine, in either solid or vapor form, to show that there is a dynamic equilibrium between these two phases.

Short answer

Use radioactive iodine as a tracer to show iodine moves between the solid and vapor phases, indicating dynamic equilibrium.

Step-by-step solution

Understand the Concept of Dynamic Equilibrium

Dynamic equilibrium occurs when the rate of sublimation (solid to gas) equals the rate of deposition (gas to solid). At this state, the number of iodine molecules in the solid phase and in the vapor remains constant over time.

Prepare Radioactive Isotope

Obtain a radioactive isotope of iodine to use as a tracer. This is crucial because the radioactive iodine can be easily detected and measured, allowing us to track its movement between the solid and vapor phases.

Introduce Radioactive Iodine into the System

Introduce the radioactive iodine into the system. This can be done either by mixing it with the solid iodine or allowing it to sublimate into the vapor phase, depending on whether you start with solid or vapor.

Monitor the Radioactivity of Both Phases

Use a Geiger counter or another suitable detection method to measure the radioactivity in both the solid and vapor phases over time. Pay attention to whether the radioactivity levels in both phases stabilize.

Analyze the Equilibrium

If the system reaches a point where the radioactivity levels in both the solid and vapor phases remain constant, this indicates that iodine is continuously moving between the two phases, thus demonstrating a dynamic equilibrium.

Key concepts

Radioactive Iodine

Radioactive iodine is a special type of iodine that emits radiation. This makes it easy to detect, helpful for scientific investigations and useful in medical treatments. When iodine is radioactive, it serves as a tracer, helping scientists track where it goes. In experiments, you might use radioactive iodine to see how iodine moves between different phases, like from solid to gas and back. By adding it to a system, you can measure how iodine transitions, offering clear insights into dynamic equilibrium.

Sublimation

Sublimation is a fascinating process where a solid turns directly into a gas without becoming a liquid first. With iodine, this happens at room temperature. When iodine undergoes sublimation, it moves from a solid state right into the vapor phase. This is crucial in experiments that want to track dynamic equilibrium, as sublimation is one side of the balance. Observing how iodine sublimates helps us understand how molecules escape from the solid and enter the gaseous state.

Deposition

Deposition is the opposite of sublimation. It is when gas turns back into a solid. In the case of iodine, the vapor molecules come back together to form solid iodine. This process is equally important to sublimation in maintaining dynamic equilibrium. Observing deposition allows us to notice how iodine molecules return to the solid state, balancing the number of molecules that have sublimated, and demonstrating the ongoing exchange between phases.

Solid Iodine

Solid iodine is how we often find this element at room temperature. It appears dark and has a shiny surface. In experiments involving dynamic equilibrium, solid iodine serves as one of the starting points. When subjected to the right conditions, solid iodine can easily transition into vapor through sublimation. As we track the movement of iodine, the solid form's role is to constantly interchange with the vapor phase, helping us understand equilibrium.

Vapor Phase

The vapor phase is the gaseous state iodine enters when it sublimates from its solid form. This phase is transparent, and you might not see it with your eyes, but its presence is critical. In an experiment studying dynamic equilibrium, the vapor phase represents iodine's ability to disperse as a gas. The transition into and out of this phase is measured to confirm that change is continuously happening and that both phases are balanced.

Tracer

A tracer is an identifiable substance that helps track the movement of materials. Radioactive iodine acts as a tracer by emitting detectable radiation. This makes it easy to follow through different phases during experiments. When iodine is used as a tracer, we monitor its shifts from solid to vapor, seeing how it disperses and recoalesces. By using a tracer, experiments can vividly demonstrate the dynamic exchanges resulting in equilibrium.

Radioactivity Measurement

Measuring radioactivity involves detecting the radiation emitted by radioactive substances like iodine. Instruments like Geiger counters are used for these measurements. In experiments on dynamic equilibrium, the radioactivity of both solid and vapor iodine is monitored over time. If the radioactivity levels in both phases become constant, this signifies that a balance—dynamic equilibrium—has been achieved. This constant measurement offers tangible proof of ongoing material exchanges between phases.