Question

\Lambdan alloy of \(\mathrm{Na}+\mathrm{K}\) is (1) liquid at room temperaturc (2) uscd in specially designed thermometers (3) both 1 and 2 (4) nonc of the above

Short answer

Option (3): both 1 and 2

Step-by-step solution

Understand the properties of Na-K alloy

Recognize that a sodium (Na) and potassium (K) alloy is a mixture of these two metals. Research their properties and how they behave in combination.

Identify the physical state at room temperature

Determine that the Na-K alloy is indeed liquid at room temperature because the melting points of sodium and potassium are both below room temperature, and their alloy usually retains those properties.

Application in thermometers

Know that Na-K alloys are used in specialized thermometers, particularly because they remain liquid over a wide range of temperatures and have favorable thermal conductivity properties.

Choose the correct option

From the given options, combine the conclusions from previous steps. Both statements (1) and (2) are accurate.

Key concepts

sodium potassium alloy

A sodium-potassium alloy, often referred to as Na-K alloy, is a mixture of sodium (Na) and potassium (K). These metals, both part of Group 1 of the periodic table, share similar properties but differ slightly in characteristics such as density and melting point. One of the remarkable features of the Na-K alloy is its physical state at room temperature. Unlike many other metal alloys, Na-K is liquid even at about 20°C. This is due to the individual properties of sodium and potassium, both of which have melting points below room temperature. Hence, when they combine, the resulting alloy retains this low melting point characteristic.

physical state of metals

Metals can exist in different states depending on their temperature. The most familiar state of metals is the solid form, as seen in everyday objects like coins, cutlery, and tools. However, metals can also exist in liquid and gaseous forms under the right conditions. Na-K alloy is a unique case where the metals are liquid at room temperature. This property can be attributed to the low melting points of sodium and potassium. Sodium melts at around 97.8°C, while potassium melts at about 63.5°C. When combined, these metals form an alloy that melts below the melting points of the individual metals, often around -12.6°C. Therefore, at room temperature (typically around 20°C), Na-K alloy remains in a liquid state.

application in thermometers

Na-K alloys have special applications, one of the most notable being in thermometers. Traditional mercury thermometers can be limited by the properties of mercury, such as its freezing point of -38.83°C. Na-K alloys, however, remain liquid over an extensive range of temperatures, making them ideal for extreme temperature measurements. These thermometers are particularly useful in scientific research and industrial applications. The excellent thermal conductivity of Na-K alloys ensures accurate and quick temperature readings. Consequently, specialized thermometers filled with Na-K alloys are used in contexts where conventional thermometers would fail.