Problem Overview:
The task involves determining whether the given chemical reactions are
exothermic (release heat) or
endothermic (absorb heat). The experiments involve measuring temperature changes during the reactions. Let's analyze each reaction step by step.
---
1. Reaction of Sodium Hydroxide Solution and Dilute Hydrochloric Acid
#### Chemical Reaction:
\[ \text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O} \]
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Type of Reaction: Neutralization reaction.
-
Heat Change: Neutralization reactions between strong acids and strong bases are typically
exothermic, meaning they release heat.
-
Observation: When hydrochloric acid is added to sodium hydroxide, the temperature of the solution increases.
#### Conclusion:
This reaction is
exothermic.
---
2. Reaction of Sodium Hydrogen Carbonate Solution and Citric Acid
#### Chemical Reaction:
\[ \text{NaHCO}_3 + \text{C}_6\text{H}_8\text{O}_7 \rightarrow \text{NaC}_6\text{H}_5\text{O}_7 + \text{H}_2\text{O} + \text{CO}_2 \]
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Type of Reaction: Acid-base reaction with the production of carbon dioxide gas.
-
Heat Change: This reaction is generally
endothermic because it involves the breaking of bonds in the reactants, which absorbs energy.
-
Observation: When citric acid is added to sodium hydrogen carbonate, the temperature of the solution decreases due to the absorption of heat.
#### Conclusion:
This reaction is
endothermic.
---
3. Reaction of Sulfuric Acid and Magnesium Ribbon
#### Chemical Reaction:
\[ \text{Mg} + \text{H}_2\text{SO}_4 \rightarrow \text{MgSO}_4 + \text{H}_2 \]
-
Type of Reaction: Metal displacement reaction.
-
Heat Change: Reactions involving the dissolution of metals in acids are typically
exothermic because they release energy as the metal ions are oxidized.
-
Observation: When magnesium ribbon reacts with sulfuric acid, the temperature of the solution increases.
#### Conclusion:
This reaction is
exothermic.
---
4. Reaction of Copper(II) Sulfate Solution and Magnesium Powder
#### Chemical Reaction:
\[ \text{CuSO}_4 + \text{Mg} \rightarrow \text{MgSO}_4 + \text{Cu} \]
-
Type of Reaction: Single-displacement reaction (metal displacement).
-
Heat Change: Similar to the previous reaction, metal displacement reactions involving active metals (like magnesium) are generally
exothermic because they release energy as the metal ions are oxidized.
-
Observation: When magnesium powder reacts with copper(II) sulfate, the temperature of the solution increases.
#### Conclusion:
This reaction is
exothermic.
---
Final Summary:
1.
Sodium Hydroxide + Hydrochloric Acid: Exothermic
2.
Sodium Hydrogen Carbonate + Citric Acid: Endothermic
3.
Sulfuric Acid + Magnesium Ribbon: Exothermic
4.
Copper(II) Sulfate + Magnesium Powder: Exothermic
Final Answer:
\[
\boxed{\text{Exothermic, Endothermic, Exothermic, Exothermic}}
\]
Parent Tip: Review the logic above to help your child master the concept of endothermic vs exothermic worksheet answers.
