Problem 55 - Chemistry: The Central Science

Question

Using the activity series(Table 4.5), write balanced chemical equations for the following reactions. If no reaction occurs, simply write NR. (a) Iron metal is added to a solution of copper(II) nitrate; (b) zinc metal is added to a solution of magnesium sulfate; (c) hydrobromic acid is added to tin metal; (d) hydrogen gas is bubbled through an aqueous solution of nickel(II) chloride; (e) aluminum metal is added to a solution of cobalt(II) sulfate.

Step-by-Step Solution

Answer

(a) Fe(s) + Cu(NO₃)₂(aq) → Fe(NO₃)₂(aq) + Cu(s) (b) NR (c) 2 HBr(aq) + Sn(s) → SnBr₂(aq) + H₂(g) (d) NR (e) 2 Al(s) + 3 CoSO₄(aq) → Al₂(SO₄)₃(aq) + 3 Co(s)

Step 1: (a) Iron metal is added to a solution of copper(II) nitrate

Iron is more reactive than copper because it lies above copper in the activity series. Therefore, iron can displace copper from copper(II) nitrate. The balanced chemical equation for this reaction is: Fe(s) + Cu(NO₃)₂(aq) → Fe(NO₃)₂(aq) + Cu(s)

Step 2: (b) Zinc metal is added to a solution of magnesium sulfate

Zinc is less reactive than magnesium because it lies below magnesium in the activity series. Therefore, zinc cannot displace magnesium from magnesium sulfate. No reaction occurs, so we write NR.

Step 3: (c) Hydrobromic acid is added to tin metal

Hydrogen is more reactive than tin because it lies above tin in the activity series. Therefore, hydrogen can displace tin from hydrobromic acid. The balanced chemical equation for this reaction is: 2 HBr(aq) + Sn(s) → SnBr₂(aq) + H₂(g)

Step 4: (d) Hydrogen gas is bubbled through an aqueous solution of nickel(II) chloride

Hydrogen is less reactive than nickel because it lies below nickel in the activity series. Therefore, hydrogen cannot displace nickel from nickel(II) chloride. No reaction occurs, so we write NR.

Step 5: (e) Aluminum metal is added to a solution of cobalt(II) sulfate

Aluminum is more reactive than cobalt because it lies above cobalt in the activity series. Therefore, aluminum can displace cobalt from cobalt(II) sulfate. The balanced chemical equation for this reaction is: 2 Al(s) + 3 CoSO₄(aq) → Al₂(SO₄)₃(aq) + 3 Co(s)

Key Concepts

Chemical Equations

Chemical equations are an essential tool in chemistry used to represent chemical reactions. They show the transformation of reactants into products using chemical formulas and other symbols. Chemical equations provide a concise way to describe reactions. They display which substances are involved and in what proportion.

To fully understand chemical equations, it's crucial to recognize that:

• They must be balanced. This means the number of atoms of each element in the reactants must equal the number of atoms in the products.
  
• The states of matter of the substances are often indicated, such as (s) for solids, (l) for liquids, (g) for gases, and (aq) for aqueous solutions.
  
• They visually represent the law of conservation of mass, meaning mass is neither created nor destroyed in a reaction.
  

When dealing with reactions such as those involving iron and copper ions, a balanced equation helps to predict the outcome of these experiments accurately.

Reactivity Series

The reactivity series is an invaluable tool for predicting the outcomes of chemical reactions, especially displacement reactions. It ranks all metals and some non-metals by their reactivity, which is their tendency to lose electrons and form positive ions.

Understanding the reactivity series can provide insights into which metals will react in certain situations:

• Higher in the series means higher reactivity. Highly reactive metals are more likely to displace less reactive ones from compounds.
  
• The series helps determine which metals can be used to extract others from their ores.
  
• It is essential in predicting the feasibility of a reaction, allowing chemists to foresee whether or not a reaction will occur.
  

Knowing the relative position of metals like iron, zinc, and copper in the reactivity series was key in solving the original exercise. Iron, being more reactive than copper, can displace it from copper nitrate, showcasing the practical application of this concept.

Displacement Reactions

Displacement reactions are a type of chemical reaction where a more reactive element displaces a less reactive element from a compound. These reactions highlight the behavior of elements based on their reactivity. The reactivity series comes into play because it indicates which elements can displace others.

Key features of displacement reactions include:

• Only more reactive elements can replace the less reactive ones from a compound, similar to iron replacing copper in the solution.
  
• These reactions are clear demonstrations of the principles of the reactivity series.
  
• They are typically single displacement reactions where one element is swapped for another.
  

For example, if zinc is less reactive than magnesium, it cannot replace magnesium in a sulfate solution, resulting in no reaction (NR), as seen in the exercise. Understanding displacement reactions can predict reactions' outcomes and help explain the behavior observed in experimental scenarios.