Observation of burning match or splint What caused the change in the burning match or splint? Na,C0,()+ – HC ) CO,)+ H00) + NaCl) 5. Type of reaction: F. Hydrogen Peroxide Reactants 1. Appearance of 2. Evidence of a Chemical Reactants Reaction H2O2(aq) light yellow 13 usble 3. _ H2O2(aq)- – H,00) + ___0,() 4. Type of chemical reaction: Questions and Problems Q1 What evidence of a chemical reaction might you see in the following cases? Refer to Table 1 a. dropping an Alka-Seltzer tablet into a glass of water release of gas. b. bleaching a stain Color change c. burning a match Heat given off d.rusting of an iron nail gas produce Q2 Balance the following equations: a. Mg(s) + HCl(aq) -Hz(8)+ MgCl2(aq) 1. Al6+ 30,6 -2_A140,6 NaCO36)+ 0 HCK) — CO26)+ LH,00+ 2 NICK) Type of reaction: Double replacement F. Hydrogen Peroxide Reactants 1. Appearance of Reactants 2. Evidence of a Chemical Reaction 113 usble H2O2(aq) Colerilets 3. 24.0,(aq) 2H,00)+10,6) 4. Type of chemical reaction: Decompatron Questions and Problems 01 What evidence of a chemical reaction might you see in the following cases? Refer to Table 1. a. dropping an Alka-Seltzer tablet into a glass of water release of gas b. bleaching a stain Color change c. burning a match Heat given off d. rusting of an iron nail gas produced Q2 Balance the following equations: Me(s) + 2 HCl(aq) – – 2 MgCl2(aq) H2(g)+ A1,036) 6. 4 AG) + 3 0,68)
The Correct Answer and Explanation is :
Q1: Evidence of Chemical Reactions
In each case, there is observable evidence of a chemical reaction, which indicates that the bonds in the reactants are being broken and new bonds are being formed. Here’s the breakdown for each scenario:
- Dropping an Alka-Seltzer tablet into water:
- Evidence: Release of gas.
- Explanation: When Alka-Seltzer (which contains sodium bicarbonate and citric acid) is dropped into water, the acid and base react to form carbon dioxide gas (CO₂). The bubbling or fizzing that occurs is evidence of this gas production.
- Bleaching a stain:
- Evidence: Color change.
- Explanation: The bleaching process involves a chemical reaction where the bleach, typically a solution of sodium hypochlorite, breaks down the chromophores in the stain. The chromophores are the molecules responsible for color, and their breakdown leads to the loss of color in the stain.
- Burning a match:
- Evidence: Heat is given off.
- Explanation: Burning involves combustion, which is a reaction between oxygen and a fuel (e.g., wood, sulfur, or phosphorus) that produces heat and light. The heat released is a significant indicator of a chemical change.
- Rusting of an iron nail:
- Evidence: Gas produced.
- Explanation: Rusting is an oxidation-reduction reaction where iron reacts with oxygen in the presence of water or moisture to form iron oxide (rust). This reaction can produce gases like hydrogen, depending on environmental conditions.
Q2: Balancing the Equations
- Balancing the Magnesium and Hydrochloric Acid Reaction:
The unbalanced equation is:
[ \text{Mg(s)} + \text{HCl(aq)} \rightarrow \text{H}_2(g) + \text{MgCl}_2(aq) ]
Balancing the atoms:
- One magnesium atom (Mg) on the left.
- One hydrogen molecule (H₂) on the right.
- Two chlorine atoms (Cl) in magnesium chloride on the right.
The balanced equation is:
[ \text{Mg(s)} + 2 \text{HCl(aq)} \rightarrow \text{H}_2(g) + \text{MgCl}_2(aq) ]
Explanation: We balance the hydrogen (H) and chlorine (Cl) by placing a coefficient of 2 in front of HCl, ensuring there are two chloride ions to balance the magnesium chloride on the right.
- Balancing the Aluminum and Oxygen Reaction:
The unbalanced equation is:
[ \text{Al}_2\text{O}_3(s) \rightarrow \text{Al}(s) + \text{O}_2(g) ]
Balancing the atoms:
- There are two aluminum atoms on the left, so place a coefficient of 2 in front of Al on the right.
- There are three oxygen atoms on the left, so place a coefficient of 3/2 in front of O₂ on the right.
The balanced equation is:
[ \text{Al}_2\text{O}_3(s) \rightarrow 2 \text{Al}(s) + \frac{3}{2} \text{O}_2(g) ]
This equation is now balanced for aluminum and oxygen atoms. To avoid fractional coefficients, multiply the entire equation by 2 to get whole numbers:
[ 2 \text{Al}_2\text{O}_3(s) \rightarrow 4 \text{Al}(s) + 3 \text{O}_2(g) ]
Thus, the final balanced equation is:
[ 2 \text{Al}_2\text{O}_3(s) \rightarrow 4 \text{Al}(s) + 3 \text{O}_2(g) ]
Type of Reactions
- The reaction of magnesium with hydrochloric acid is a single replacement reaction because magnesium replaces hydrogen in hydrochloric acid.
- The decomposition of aluminum oxide is a decomposition reaction because a single compound is breaking down into two products, aluminum and oxygen.
Summary
These chemical reactions provide clear evidence through changes like gas production, heat release, and color change, which indicate that new substances are formed. Balancing chemical equations ensures that the law of conservation of mass is followed, meaning the same number of atoms are present on both sides of the equation.