Question

How can you use the activity series to determine whether a metal will dissolve in acids such as HCl or HBr?

Short answer

To use the activity series, compare the position of the metal with that of hydrogen; if the metal is higher in the series, it will react with and dissolve in acids such as HCl or HBr.

Step-by-step solution

Understanding the Activity Series

The activity series is a list of metals arranged in order of decreasing reactivity with acids and water. A metal will replace hydrogen from an acid if it is higher on the activity series than hydrogen.

Determining Metal Reactivity

To determine if a metal will dissolve in an acid, locate the metal and hydrogen in the activity series. If the metal is above hydrogen, it can displace hydrogen from the acid and will dissolve. If it is below, no reaction will occur.

Applying the Activity Series to HCl or HBr

For acids like HCl (hydrochloric acid) or HBr (hydrobromic acid), find the position of the metal in the activity series relative to hydrogen. If the metal is above hydrogen, the metal will react with the acid to produce hydrogen gas and a metal salt, thus dissolving in the process.

Key concepts

Reactivity of Metals

The reactivity of metals is an important chemical property that determines how a metal behaves when it comes into contact with other substances. Metals vary widely in their reactivity. For instance, alkali metals like sodium and potassium are highly reactive, especially with water, while noble metals like gold and silver show very little reactivity.

Understanding the reactivity of metals is crucial because it helps us predict how metals will interact with other elements. The activity series is a useful tool in this regard. It ranks metals from most reactive to least reactive. This ranking is based on the tendency of a metal to lose electrons and form positive ions. Highly reactive metals, which are at the top of the activity series, can easily lose electrons as compared to those lower down the list.

When it comes to metal-acid reactions, the reactivity of a metal strongly influences whether it will react to displace hydrogen from an acid. Metals higher in the activity series than hydrogen have the potential to do so, while those lower will not react under normal conditions.

Metal-Acid Reactions

Metal-acid reactions involve a metal reacting with an acid to produce hydrogen gas and a salt. These reactions are a type of single-replacement reaction, where a metal takes the place of hydrogen in the acid. The general form of such a reaction can be represented by the equation:
\[ \text{Metal} + \text{Acid} \rightarrow \text{Hydrogen gas} + \text{Metal Salt} \]

For a metal to react with an acid and dissolve, the metal must be more reactive than the hydrogen in the acid. If we consider the reaction of zinc with hydrochloric acid, for example, we will find that zinc replaces the hydrogen atoms to form zinc chloride (\( \text{ZnCl}_2 \)) and hydrogen gas (\( H_2 \)).

This happens because zinc is above hydrogen in the activity series. If the same is attempted with copper, which is below hydrogen, there will be no reaction—copper will not dissolve in hydrochloric acid. Knowing the position of metals in the activity series, thus, allows us to predict the outcomes of such reactions.

Predicting Chemical Reactions

Predicting chemical reactions is a key aspect of chemistry that involves understanding the conditions under which substances will react and what products they will form. The activity series is an indispensable tool for predicting whether certain single-replacement reactions will occur, especially metal-acid reactions.

To predict accurately, chemists rely on the known reactivity of metals (as indicated by the activity series), reactivity trends within groups and periods in the periodic table, and knowledge of reaction mechanisms. For instance, if we want to know whether a metal will dissolve in a particular acid, we'll look at the activity series to see if the metal is positioned above hydrogen. If so, it's a good indicator that the metal will react with the acid to form a metal salt and release hydrogen gas.

It's important to note that other factors, such as concentration, temperature, and presence of catalysts or inhibitors, can also affect the outcome of a reaction. As such, while the activity series provides a valuable guideline, it must be considered in the context of the entire reaction environment to make reliable predictions.