Problem 56 - Chemistry: The Central Science in SI Units, Global Edition

Question

Using the activity series (Table 4.5 ), write balanced chemical equations for the following reactions. If no reaction occurs, write NR. (a) Nickel metal is added to a solution of copper(II) nitrate, (b) a solution of zinc nitrate is added to a solution of magnesium sulfate, (c) hydrochloric acid is added to gold metal, (d) chromium metal is immersed in an aqueous solution of cobalt(II) chloride, (e) hydrogen gas is bubbled

Step-by-Step Solution

Answer

(a) \(Ni(s) + Cu(NO_3)_2(aq) \rightarrow Ni(NO_3)_2(aq) + Cu(s)\) (b) NR (c) NR (d) \(Cr(s) + CoCl_2(aq) \rightarrow CrCl_2(aq) + Co(s)\) (e) NR

Step 1: Check activity series for Nickel and Copper

Refer to the activity series and find that Nickel (Ni) is more reactive than Copper (Cu). A reaction will occur.

Step 2: Write the balanced chemical equation

The balanced chemical equation for this reaction is: \(Ni(s) + Cu(NO_3)_2(aq) \rightarrow Ni(NO_3)_2(aq) + Cu(s)\) Step 2: Reaction between a solution of zinc nitrate and a solution of magnesium sulfate

Step 3: Check activity series for Zinc and Magnesium

Refer to the activity series and find that Zinc (Zn) is less reactive than Magnesium (Mg). No reaction will occur.

Step 4: Write the balanced chemical equation

Since no reaction occurs, write NR. Step 3: Reaction between hydrochloric acid and gold metal

Step 5: Check activity series for Hydrogen and Gold

Refer to the activity series and find that Hydrogen (H) is more reactive than Gold (Au). No reaction will occur.

Step 6: Write the balanced chemical equation

Since no reaction occurs, write NR. Step 4: Reaction between chromium metal and an aqueous solution of cobalt(II) chloride

Step 7: Check activity series for Chromium and Cobalt

Refer to the activity series and find that Chromium (Cr) is more reactive than Cobalt (Co). A reaction will occur.

Step 8: Write the balanced chemical equation

The balanced chemical equation for this reaction is: \(Cr(s) + CoCl_2(aq) \rightarrow CrCl_2(aq) + Co(s)\) Step 5: Reaction between hydrogen gas and silver nitrate solution

Step 9: Check activity series for Hydrogen and Silver

Refer to the activity series and find that Hydrogen (H) is more reactive than Silver (Ag). No reaction will occur.

Step 10: Write the balanced chemical equation

Since no reaction occurs, write NR.

Key Concepts

Reactivity of Metals

The reactivity of metals is a fascinating concept that helps predict the outcome of chemical reactions involving metals. Imagine it as a competitive ranking, where metals with higher reactivity can displace those with lower reactivity from compounds. The activity series is like a list that guides us in understanding these preferences. For example:

• Metals at the top of the list, such as potassium and lithium, are highly reactive.
• Less reactive metals like gold or silver are found at the bottom.

Using this series, one can foresee whether a metal can successfully displace another. For instance, in a reaction between nickel and copper (II) nitrate, since nickel is more reactive, it can replace copper in the compound. This helps us predict and explain chemical behaviors with ease!

Balanced Chemical Equations

Balanced chemical equations are crucially important in chemistry as they illustrate how atoms are conserved in a chemical reaction. Consider it like a balanced scale, where both sides must weigh the same. Every reaction follows the law of conservation of mass, meaning that atoms are neither lost nor gained but rearranged. An equation is balanced by ensuring:

• Same number of each type of atom on both reactant and product sides.
• Use of smallest whole numbers as coefficients to balance the atoms.

For instance, the balanced equation for the displacement of copper by nickel is:\[ Ni(s) + Cu(NO_3)_2(aq) \rightarrow Ni(NO_3)_2(aq) + Cu(s) \]Here, you can see each element balances perfectly, making the equation correct and representative of what happens in reality.

Displacement Reactions

Displacement reactions are exciting processes where one element replaces another in a compound. This type of reaction primarily occurs due to the difference in reactivity of elements. The activity series becomes handy here, where a more reactive metal can displace a less reactive metal from its compound.In practice, this means:

• If a metal is higher in the activity series, it will replace another lower metal in compounds.
• No reaction occurs if the metal attempting to displace is lower in reactivity.

An example is the displacement of cobalt by chromium in the reaction:\[ Cr(s) + CoCl_2(aq) \rightarrow CrCl_2(aq) + Co(s) \]Chromium successfully displaces cobalt due to its higher ranking in the activity series. Understanding these reactions enhances our grasp of the dynamic nature of chemistry.