A redox reaction (reduction-oxidation reaction) is a type of chemical reaction that involves a transfer of electrons between two species. This transfer can be identified by a change in the oxidation states of the atoms involved. Oxidation is the loss of electrons (increase in oxidation state), and reduction is the gain of electrons (decrease in oxidation state).
B) CuO + H₂ → Cu + H₂O
Comparing reactants to products:
Since both oxidation and reduction occur, this is a redox reaction.
The question asks for the definition of corrosion. Corrosion is a natural process that converts a refined metal into a more stable form, such as its oxide, hydroxide, or sulfide. It is the gradual destruction of materials (usually metals) by chemical and/or electrochemical reaction with their environment.
D) All of the above. This option correctly identifies that rusting of iron, tarnishing of silver, and the formation of a green coating on copper are all instances of corrosion.
Rancidity is a common phenomenon that affects food items, particularly those rich in fats and oils. Understanding its cause is crucial for food preservation. This question asks for the primary cause of rancidity.
B) Air oxidation — Air oxidation, specifically the reaction of oxygen with unsaturated fatty acids in food, is the primary chemical process that leads to rancidity. This process breaks down fats and oils into compounds that produce undesirable smells and tastes.
A double displacement reaction is a type of chemical reaction where two compounds react, and the positive ions (cations) and negative ions (anions) of the two reactants switch places, forming two new compounds. This often results in the formation of a precipitate, a gas, or water.
Correct Option: B) BaCl₂ + Na₂SO₄ → BaSO₄ + NaCl
This is a double displacement reaction because the cations (\(\text{Ba}^{2+}\) and \(\text{Na}^+\)) and anions (\(\text{Cl}^-\) and \(\text{SO}_4^{2-}\)) of the two reactant compounds exchange places to form two new compounds, barium sulfate (\(\text{BaSO}_4\)) and sodium chloride (\(\text{NaCl}\)). Barium sulfate is a white precipitate.
The question asks to identify the reaction that represents thermal decomposition. Thermal decomposition is a type of chemical reaction where a single compound breaks down into two or more simpler substances when heated.
A) \( \text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2 \) represents thermal decomposition because calcium carbonate breaks down into calcium oxide and carbon dioxide upon heating.
The question asks about the product formed when magnesium burns in air. Burning is a chemical reaction, specifically a combustion reaction, where a substance reacts rapidly with oxygen, usually producing heat and light. Air primarily consists of nitrogen (about 78%) and oxygen (about 21%), along with small amounts of other gases.
Correct Option: C) Magnesium oxide