REPORT SHEET LAB: Chemical Reactions and Equations 10. Magnesium and Oxygen 1. Initial appearance of Mg: shiny silver 2. Evidence of chemical reaction: The Mg ignited and turned into a grayish-white powder. 3. Balance: Mg(s) + O2(g) → MgO(s) 4. Type of chemical reaction: Combustion Zinc and Copper(II) Sulfate Time CuSO4(aq) + Zn(s) Appearance Evidence of a Chemical Reaction Appearance 1. Initial: Blue solution 2. After reaction: Black precipitate 30 min Zn(s) + CuSO4(aq) → Cu(s) + ZnSO4(aq) Type of chemical reaction: Single displacement
The Correct Answer and Explanation is:
REPORT SHEET LAB: Chemical Reactions and Equations 10
Magnesium and Oxygen
- Initial appearance of Mg: Shiny silver
- Evidence of chemical reaction: The magnesium ignited with a bright white flame and formed a grayish-white powder.
- Balanced chemical equation:
2Mg(s) + O₂(g) → 2MgO(s) - Type of chemical reaction: Combustion (also a Combination/Synthesis reaction)
Zinc and Copper(II) Sulfate
- Initial appearance of solution: Blue solution (due to Cu²⁺ ions)
- Evidence of a chemical reaction: The blue color faded, a reddish-brown solid (copper) formed, and the zinc became dull.
- Balanced chemical equation:
Zn(s) + CuSO₄(aq) → Cu(s) + ZnSO₄(aq) - Type of chemical reaction: Single Displacement
Explanation
This lab demonstrates two important types of chemical reactions: combustion and single displacement. In the first reaction, magnesium (Mg) is a shiny, silver metal. When heated in the presence of oxygen (O₂), it combusts, producing a bright white flame. This reaction forms magnesium oxide (MgO), a white or grayish powder. The balanced chemical equation is:
2Mg(s) + O₂(g) → 2MgO(s).
This is classified as a combustion reaction because it involves a substance reacting with oxygen, releasing energy as light and heat. It is also a synthesis reaction, where two reactants combine to form a single product.
In the second reaction, solid zinc (Zn) is placed in an aqueous solution of copper(II) sulfate (CuSO₄), which is blue due to dissolved Cu²⁺ ions. Over time, zinc displaces the copper from the solution. This is evident when the blue color fades and a reddish-brown solid (copper metal) forms on the zinc surface. The balanced equation is:
Zn(s) + CuSO₄(aq) → Cu(s) + ZnSO₄(aq).
This is a single displacement reaction because a more reactive metal (zinc) displaces a less reactive metal (copper) from its compound. The zinc goes into solution as Zn²⁺, forming zinc sulfate (ZnSO₄), while copper is deposited as a solid.
These reactions show how observable changes—color changes, formation of solids, and light or heat emission—indicate chemical changes, confirming the transformation of substances into new products with different properties.
