EmSAT Chemistry Flashcards

What is the oxidation state of sulfur in H₂SO₄?

Answer: +6

In H₂SO₄: H is +1 (×2 = +2), O is −2 (×4 = −8). For the molecule to be neutral: +2 + S + (−8) = 0, so S = +6.

What is a redox reaction?

Answer: A reaction where electrons are transferred between species

A redox (reduction-oxidation) reaction involves the transfer of electrons between chemical species. One species is oxidized (loses electrons) and another is reduced (gains electrons).

Which element is reduced in: Zn + CuSO₄ → ZnSO₄ + Cu?

Answer: Copper

Cu²⁺ gains 2 electrons to become Cu (solid). Gaining electrons is reduction. Zinc is oxidized (loses electrons) to become Zn²⁺.

What is the rate of a chemical reaction?

Answer: The change in concentration of reactants/products per unit time

Reaction rate is defined as the change in concentration of reactants or products per unit time. It tells us how quickly a reaction proceeds.

Which factor does NOT affect reaction rate?

Answer: Color of the reactants

Reaction rate is affected by temperature, concentration, catalyst presence, and surface area. The color of reactants is not a factor that affects how fast molecules react.

What is a catalyst?

Answer: A substance that speeds up a reaction without being consumed

A catalyst speeds up a chemical reaction by providing an alternative pathway with lower activation energy. Crucially, it is not consumed in the reaction and can be reused.