2ND QUARTER REVIEWER

In the compound H₂O₂, why is the oxidation number of oxygen -1, not -2?

• Hydrogen is always +1.

• The compound is unstable.

• The compound is a peroxide.

• Oxygen can have variable oxidation states.

How can the oxidation number of an element in a compound be determined?

By knowing the __________.

• charge of the compound.

• electronegativity of the element.

• oxidation numbers of other elements in the compound.

• All of the above.

How do you determine the charge on a transition metal ion in a compound like FeCl₂?

By ____________.

• using a periodic table

• using a Roman numeral

• knowing the group number of iron

• knowing the charge on the chloride ion

Why do ionic compounds form when metal and non-metal elements combine?

Due to ___________.

• electron transfer creating opposite charges

• electron sharing between atoms

• covalent bond formation

• van der Waals forces

Why was Avogadro's number chosen to be 6.022×10²³?

• It was randomly selected.

• It's based on the mass of hydrogen.

• It represents Earth's atmospheric pressure.

• It relates to the number of atoms in 12g of carbon-12.

How would you explain the balanced equation 2𝐻₂+𝑂₂→2𝐻₂𝑂 in terms of conservation of mass?

• The number of atoms changes but mass remains constant.

• Both mass and atoms remain unchanged throughout.

• The number of atoms on each side must be equal.

• The reactants gain mass during the reaction.

How does a neutralization reaction demonstrate conservation of charge?

• maintaining equal numbers of positive and negative ions

• releasing energy in the form of heat

• changing the color of indicators

• producing water molecules only

Why does a combustion reaction often result in an increase in entropy of the system?

Because it ________________

• releases heat energy only

• decreases molecular movement

• absorbs energy from surroundings

• converts solid fuel into gaseous products

How does the presence of a catalyst affect the activation energy in a chemical reaction?

• It provides an alternative reaction pathway with lower activation energy.

• It changes the overall energy of products.

• It increases the activation energy barrier.

• It makes the reaction more endothermic.

Which explains the spontaneous nature of rusting despite being a slow process?

• The high activation energy barrier.

• The presence of water as a catalyst.

• The negative Gibbs free energy change.

• The formation of complex intermediates.