Question

Select T/F for each of the following statements regarding Alkali Metals:

The chemical reactions associated with lithium in a reacted state (such as lithium peroxide and lithium hydroxide) are useful for applications pertaining to modifying atmospheric composition.

Lithium is the smallest metal atom within the alkali group.

Francium is the most abundant of all metals and is therefore the least expensive metal per kilogram.

The primary reason that alkali metals are submerged in mineral oil for storage is that the mineral oil changes color when these metals undergo radioactive decay, thereby acting as a color indicator for radiation release.

The outer s1 electrons of alkali metal atoms are very loosely bound to their positive nuclei, rendering these metals fairly reactive, chemically, when compared to other metals.

Unlike other alkali metal atoms, the sole valence electron of a Li atom is not shielded from the nucleus by a filled pshell. Therefore, Li tends to be the least reactive when compared to other alkali metals.

Select T/F for each of the following statements regarding Alkaline Metals:

Beryllium has a lower melting point than aluminum.

Beryllium metal is toxic.

Aluminum has a higher density than magnesium.

Beryllium and Magnesium are the only alkaline metals that have use as structural materials, since Ca, Sr, Ba, and Ra are susceptible to corrosion in air.

A significant fraction of magnesium that is produced ends up acting as an alloying element in aluminum.

Magnesium is highly resistant to corrosion, even when placed in contact with other metals.

Select T/F for each the following statements:

The Na-K alloy system features a eutectic point, and this composition is useful as a high-melting point liquid coolant with low thermal conductivity, for applications where the alloy is in an inert environment.

The relatively high thermal expansion coefficient of alkali metals is one indicator that these metals feature relatively weak metallic bonds.

Beryllium is useful for x-ray applications, such as an x-ray transparent window, because beryllium is fairly transparent to x-rays.

Of all elements found in Earth's crust, only eight have a weight percentage above 1%, and four of these eight are either alkali or alkaline metals.

The melting point and elastic modulus of beryllium are remarkably high, compared to its neighbors on the periodic table.

  

Sodium metal is the most expensive metal per kilogram (comparing approximate bulk prices).

Answer 1

Ans :-

Select T/F for each of the following statements regarding Alkali Metals:

1. TRUE , The chemical reactions associated with lithium in a reacted state (such as lithium peroxide and lithium hydroxide) are useful for applications pertaining to modifying atmospheric composition. Because, Lithium peroxide and lithium hydroxide react with atmospheric carbon dioxide as :

Li₂O₂ + CO₂ ----------------> Li₂CO₃ + 1/2 O₂

2 LiOH + CO₂ ----------------> Li₂CO₃ + H₂O

Hence the given statement is true.

2. TRUE, Lithium is the smallest metal atom within the alkali group. Because, Li lies at the top of the group and we know that on moving down the group atomic size increases.

Hence the given statement is true.

3. FALSE ,Francium is the most abundant of all metals and is therefore the least expensive metal per kilogram. It is the most reactive metal ( i.e. radioactive).

Hence the given statement is false.

4. FALSE ,The primary reason that alkali metals are submerged in mineral oil for storage is that the mineral oil changes color when these metals undergo radioactive decay, thereby acting as a color indicator for radiation release. Because, alkali metals are stored in oil as they reacts with oxygen or moisture and catch fire easily.

Hence the given statement is true.

5. TRUE ,The outer 1S electrons of alkali metal atoms are very loosely bound to their positive nuclei, rendering these metals fairly reactive, chemically, when compared to other metals.

Hence the given statement is true.

6. TRUE ,Unlike other alkali metal atoms, the sole valence electron of a Li atom is not shielded from the nucleus by a filled p-shell. Therefore, Li tends to be the least reactive when compared to other alkali metals.

Hence the given statement is true.