Video: Identifying the Element That Is a Rare Metal That Does Not React with Acids in a Set of Element Symbols

Which of the following is a rare metal that does not react with acids? [A] Zn [B] Pt [C] Li [D] O [E] U


Video Transcript

Which of the following is a rare metal that does not react with acids? (A) Zn, (B) Pt, (C) Li, (D) O, or (E) U.

First, let’s identify the elements from the symbols given in the possible answers. Zn is zinc; Pt, platinum; Li, lithium; O, oxygen; and U, uranium. Elements are arranged on the periodic table according to similar properties. This periodic table shows where the metals, metalloids, and nonmetals are located.

The question asks about a metal. In general, metals show similar properties. All metals are solids in their standard state, except for mercury, which is a liquid. Metals are shiny; are malleable, which means they can be hammered into flat sheets; ductile, which means they can be pulled or drawn into thin wires. And metals conduct electricity and heat very well. In addition to that, some metals tend to react in similar manners. For example, many react with acids, but not all.

Let’s insert the possible answers given to us onto the periodic table to determine which are metals and which are not. Immediately, we can see that oxygen is not a metal but a nonmetal. So we can rule out oxygen as an answer. Oxygen does not have the properties of a metal. It is not shiny, malleable, ductile, nor is it a good conductor of heat and electricity. The remaining four possible answers are all metals. But which are considered rare?

The term “rare” means not occurring very often. When used to describe an element, “rare” can mean found only in small amounts in the Earth’s crust, in other words, a small percentage abundance. The relative percent abundance of each of the four metals given is shown in decreasing order. With lithium occurring more abundantly in the Earth’s crust, in soil, rocks, and waters. Zinc slightly less, uranium slightly less but still fairly abundant, and platinum occurring at a much, much smaller percent than the other metals. Platinum is thus a rare metal. Other rare metals include Rh, rhodium; Pd, palladium; Ag, silver; Au, gold; and Ru, ruthenium.

Because of the scarcity of the rare metals, their market value or market cost is very high compared to other metals which are more abundant. Many of these rare metals also have very useful properties, used in very small amounts as effective catalysts in industry. So platinum, being rare and a metal, looks like a good candidate for our answer. But does it react with acids or not?

Zinc, lithium, and uranium are all highly reactive metals and react spontaneously with acids, such as hydrochloric acid, HCl aqueous. Zinc and lithium when they react with hydrochloric acid produce chlorides as products as well as H2 or hydrogen gas. Uranium when it reacts with hydrochloric acid produces several complex uranium compounds and hydrogen gas. Platinum, however, under normal conditions is unreactive and does not react with acids, such as hydrochloric acid. Platinum is an example of an inert metal. Very special conditions, such as extremely high temperatures or pressures, are needed to induce an inert metal, such as platinum, to react with an acid.

The question asked, which rare metal does not react with acids? Zinc, lithium, and uranium are not possible answers because they do react with acids. Platinum is a rare metal which does not react with acids and is our answer.

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