What is the phase of the standard states of the following ele- ments and compounds? (a) NH3 (b) Fe (c) N2 (d) Br2

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Identify the standard state of each substance at 1 atm pressure and a temperature of 25°C (298 K).

For NH3 (ammonia), recognize that it is a gas under standard conditions. Therefore, the phase of NH3 in its standard state is gaseous.

For Fe (iron), note that it is a solid metal at room temperature and pressure. Thus, the phase of Fe in its standard state is solid.

For N2 (nitrogen), understand that it is a diatomic molecule that exists as a gas at standard conditions. Hence, the phase of N2 in its standard state is gaseous.

For Br2 (bromine), consider that it is a liquid at room temperature, making it unique among the halogens. Therefore, the phase of Br2 in its standard state is liquid.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Standard State

The standard state of a substance refers to its physical state (solid, liquid, or gas) at a specified temperature and pressure, typically 1 bar (100 kPa) and 25°C (298 K). Understanding the standard state is crucial for determining the phase of elements and compounds under standard conditions, as it provides a reference point for thermodynamic calculations.

Phase of Matter

The phase of matter describes the distinct forms that different phases of matter take on. The three primary phases are solid, liquid, and gas, each characterized by different properties such as shape, volume, and molecular arrangement. For example, while metals like iron (Fe) are solid at room temperature, gases like nitrogen (N2) exist in a gaseous state.

Element vs. Compound

Elements are pure substances that consist of only one type of atom, while compounds are substances formed from two or more different types of atoms chemically bonded together. This distinction is important when identifying the phases of substances, as elements like iron (Fe) and nitrogen (N2) exhibit different physical states compared to compounds like ammonia (NH3) and bromine (Br2) under standard conditions.

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