Which of the following statement(s) is(are) true? a. The...

Which of the following statement(s) is(are) true? a. The alkali metals are found in the earth's crust in the form of pure elements. b. Gallium has one of the highest melting points known for metals. c. When calcium metal reacts with water, one of the products is $\mathrm{H}_{2}(\mathrm{~g})$ d. When $\mathrm{AlCl}_{3}$ is dissolved in water, it produces an acidic solution. e. Lithium reacts in the presence of excess oxygen gas to form lithium superoxide.

Which of the following statement(s) is(are) true?
a. The alkali metals are found in the earth's crust in the form of pure elements.
b. Gallium has one of the highest melting points known for metals.
c. When calcium metal reacts with water, one of the products is $\mathrm{H}_{2}(\mathrm{~g})$
d. When $\mathrm{AlCl}_{3}$ is dissolved in water, it produces an acidic solution.
e. Lithium reacts in the presence of excess oxygen gas to form lithium superoxide.

Key Concepts

Occurrence of Elements in Nature

This concept deals with the natural state of elements in the environment, particularly how reactive metals are typically not found in their pure elemental form in nature but rather in compound forms due to their high reactivity. It emphasizes that many elements, especially alkali and alkaline earth metals, are extracted from minerals and ores rather than occurring as free elements.

Metal Melting Points

This concept involves understanding the factors that affect the melting points of metals, including atomic structure and bonding. It explains that metals have a wide range of melting points, and claims about unusually high or low melting points require careful evaluation based on the element's position in the periodic table and its unique physical properties.

Reactivity of Metals with Water

This concept covers the chemical behavior of metals when they interact with water. Many metals, particularly those that are highly reactive, undergo a reaction with water to form hydroxides and hydrogen gas. This is a fundamental reaction type in inorganic chemistry that helps illustrate the properties of reactive metals such as alkali metals and some alkaline earth metals.

Hydrolysis of Metal Halides

This concept explains how certain metal halides react with water, a process known as hydrolysis, which may result in the solution becoming acidic. It involves the interaction of metal ions and water molecules, leading to the formation of acids due to the release of hydrogen ions and the restructuring of the compound in an aqueous environment.

Formation of Metal Oxides and Related Compounds

This concept pertains to the different types of oxides that metals form when reacting with oxygen, including normal oxides, peroxides, and superoxides. It highlights the role of the metal’s chemical properties and the conditions of the reaction in determining which oxide species is formed, making it a key topic in understanding the oxidation behavior of elements such as the alkali metals.

Transcript

00:03 So here we are given five statements and we're asked to determine whether these are true or false.

00:12 So the first one asks us whether we can find alkali metals is pure elements in earth's crust.

00:20 And the answer to this is that's false because, okay, that's false because alkaline metals you may remember are never found in nature uncombined because they're so reactive.

00:37 They're very unstable.

00:39 They react with other melons very quickly, and so they'll bond with nearly anything.

00:46 The next question asks about gallium, and it asserts that it has a high melting point, one of the highest known for metals.

00:57 And this is also false.

01:01 If you want to see a, it's kind of neat.

01:05 Just your body heat, if you hold gallium in your hand, it can actually melt it.

01:10 So that's a low melting point, not a high melting point for a metal.

01:13 Because not many other metals you can just hold and it'll start to melt.

01:19 C, it asks about when calcium reacts with water, it asserts that hydrogen is produced.

01:27 Okay? and this is true because the reaction here is calcium plus water.

01:40 Will produce calcium hydroxide and hydrogen gas.

01:50 Okay, so that assertion is true.