A) Give one example each of: (i) Suspension (ii) Colloid b) What is meant by isoelectronic series c) Define (i) heat of formation (ii) heat of combustion d) Explain briefly why helium is more preferable to hydrogen as a rocket fuel. e) Give the shapes of (i) CO2 (ii) CH4 (iii) NH3

Here are the solutions to your questions:

a) Give one example each of:

i) Suspension
An example of a suspension is $\boxed{\text{muddy water}}$.

ii) Colloid
An example of a colloid is $\boxed{\text{milk}}$.

b) What is meant by an isoelectronic series?
An isoelectronic series refers to a group of atoms or ions that all possess the $\boxed{\text{same number of electrons}}$.

c) Define:

i) Heat of formation
The heat of formation is the $\boxed{\text{enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions}}$.

ii) Heat of combustion
The heat of combustion is the $\boxed{\text{enthalpy change when one mole of a substance is completely burned in oxygen under standard conditions}}$.

d) Explain briefly why helium is more preferable to hydrogen as a rocket fuel.
Helium is more preferable to hydrogen in certain rocket applications (e.g., as a pressurant) because $\boxed{\text{helium is an inert gas, meaning it is non-flammable and non-explosive, making it much safer to handle and store compared to highly flammable and explosive hydrogen}}$.

e) Give the shapes of:

i) $CO_2$
The shape of $CO_2$ is $\boxed{\text{linear}}$.

ii) $CH_4$
The shape of $CH_4$ is $\boxed{\text{tetrahedral}}$.

iii) $NH_3$
The shape of $NH_3$ is $\boxed{\text{trigonal pyramidal}}$.