Foundations in chem

Question 1

What is a limiting reagent?

Answer 1

A limiting reagent is the reactant that is NOT in excess and when completely used up stops the reaction.

• good example would be hydrogen and oxygen, if equal mols of both reacted then half of oxygen molecule would be left behind, this means hydrogen is the limiting reagent.

Question 2

What assumptions can be made from a hydrated salt experiment?

Answer 2

1. All the water has not been lost - heat to constant mass to ensure all the water has been removed.
2. There has been further decomposition - when heated strongly further copper(II) sulphate decomposes to form black copper (II) oxide.

Question 3

What do reactions with high atom economies do?

Answer 3

• produce a large proportion of desired products and few waste products.
• are important for sustainability as they make the best of natural resources.

Question 4

How sustainable is atom economy really?

Answer 4

• Process used readily available reactants and energy is needed for producing steam, costs for starting materials are low.
• Other reactions might have higher atom economy but low percentage yields. Efficiency depends on both factors.

Question 5

What is the meaning of a principle quantum number?

Answer 5

• Shell number or the energy level number.