Metal + Non-oxidizing Acid Reactions Chemistry Tutorial

Key Concepts

• Non-oxidizing acids include dilute hydrochloric acid (HCl_(aq)) and dilute sulfuric acid (H₂SO_4(aq)).

• The ease with which a metal reacts is known as its activity.

  A more active metal will react more readily with an acid than a less active metal.

  Group 1 (IA or alkali) metals and Group 2 (IIA or alkaline earth) metals are more active than transition metals.

  Silver, gold and platinum are not active metals. They are known as noble metals^# (or as inactive metals).

• All metals which are more active than lead react with dilute hydrochloric acid or dilute sulfuric acid^##.
• Metals that react with these acids produce a metal salt and hydrogen gas:
  

  metal	+	non-oxidizing acid	→	metal salt	+	hydrogen gas
  metal	+	dilute hydrochloric acid	→	metal chloride	+	hydrogen gas
  metal	+	dilute sulfuric acid	→	metal sulfate	+	hydrogen gas


Heat is also produced during these reactions.^###
A more active metal will produce heat energy faster than a less active metal.

Reactions of Some Common Metals with Dilute HCl_(aq) and Dilute H₂SO_4(aq)

Example 1

Question: A student poured 25 mL of dilute hydrochloric acid into each of three test tubes labelled A, B and C.
The student also had equal amounts of clean copper, iron and magnesium.
To test tube A she added the copper.
To test tube B she added the iron.
To test tube C she added the magnesium.
In which test tube would the metal disappear first?

Response: The more active the metal the more readily it will react with the acid.
In order of increasing activity the metals are: copper < iron < magnesium
The metal that will react most readily is the magnesium, so it will disappear first.
Test tube C contained the magnesium.
The metal in test tube C will disappear first.

Example 2

Question:In order to determine the relative activity of two different metal samples a student performed the following experiment:
100 mL of 0.1 mol L^-1 HCl_(aq) was added to each of three 250 mL beakers labelled B1, B2 and B3.
A thermometer was suspended in each beaker and the temperature of the acids recorded.
Equal amounts of each metal sample were measured out.
One of the measured metal samples was placed in beaker B1, the other measured metal sample was placed in beaker B2.
The temperature of the solutions in the beakers was recorded every 2 minutes for 10 minutes:

Response:The metal that reacts more readily with the acid will be the more active metal.
When metals react with acid they release heat energy.
The more rapidly the reaction takes place, the more heat will be released faster, so the temperature of the solution will increase more rapidly.
The temperature in beaker B2 increased more rapidly than the temperature in beaker B1.
The reaction taking place in beaker B2 is more rapid than the reaction taking place in beaker B1.
Beaker B2 contains the more active metal.

Example 3

Question:A biochemist has just been given a huge grant to upgrade the laboratory and has decided to install metal benchtops in the laboratory.
The only acid this biochemist ever uses is dilute hydrochloric acid.
The benchtops can be produced in aluminium, iron or platinum.
Which benchtop would last the longest time in the biochemist's laboratory?

Response:The metals in order of activity from most active to least active are: aluminium > iron > platinum
The metal which is least active is least likely to react with the dilute hydrochloric acid, so it will last the longest as a laboratory benchtop.
Platinum is the least active (but most expensive!) so it would last the longest time as a benchtop.