The cup shown below provides an example of tarnish, a smashville247.netical change caused by the reaction ofsilver metal with hydrogen sulfide gas. Hydrogen sulfide gas is created by some industrial processes, or as a result of decaying animal or plant materials:

\<2 \ceAg + \ceH_2S \rightarrow \ceAg_2S + \ceH_2\>

The tarnish deserve to be removed using a number of polishes, yet the process also gets rid of a tiny amount the silver in addition to the tarnish.

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Figure $$\PageIndex1$$: A tarnished silver cup. (CC BY-NC; CK-12)

A single-replacement reaction is a reaction in which one facet replaces a similar element in a compound. The general form of a single-replacement (also dubbed single-displacement) reaction is:

\<\ceA + \ceBC \rightarrow \ceAC + \ceB\>

In this basic reaction, facet $$\ceA$$ is a metal and replaces facet $$\ceB$$(also a metal) in the compound. When the element that is act the replacing is a nonmetal, it have to replace another nonmetal in a compound, and also the basic equation becomes:

\<\ceY + \ceXZ \rightarrow \ceXY + \ceZ\>

(Where $$\ceY$$ is a nonmetal and replaces the nonmetal $$\ceZ$$ in the compound v $$\ceX$$.)

### Hydrogen Replacement

Many steels react conveniently with acids and when they perform so, one of the products of the reaction is hydrogen gas. Zinc reacts v hydrochloric acid to produce aqueous zinc chloride and hydrogen (figure below).

\<\ceZn \left( s \right) + 2 \ceHCl \left( aq \right) \rightarrow \ceZnCl_2 \left( aq \right) + \ceH_2 \left( g \right)\>

In a hydrogen replacement reaction, the hydrogen in the acid is changed by an energetic metal.

Figure $$\PageIndex2$$: Zinc steel reacts v hydrochloric mountain to give off hydrogen gas in a single-displacement reaction.

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(CC BY-NC; CK-12)

Some steels are so reactive the they are qualified of replacing the hydrogen in water. The products of together a reaction room the steel hydroxide and hydrogen gas. All team 1 steels undergo this type of reaction. Sodium reacts vigorously v water to produce aqueous sodium hydroxide and hydrogen (see number below).