Expert Chemistry Tutoring

Q8. A sample of iron(III) oxide (Fe2O3) has a mass of 15.0 g. Calculate the number of moles of iron atoms present in the sample. Given: Ar Fe = 55.85. (4 marks)

Q9. The following equation represents a reaction between sodium and hydrochloric acid:

a) Balance the equation. (2 marks)

b) State the type of reaction that is taking place. (1 mark)

Q10. Define the term "isotopes". Explain how isotopes of an element differ and give two examples of how isotopes can be used in everyday life. (6 marks)

- An element is a pure substance that cannot be broken down into simpler substances by chemical means.

- An ionic bond is a strong electrostatic attraction between positively and negatively charged ions.

- Ions are formed when atoms transfer electrons to each other.

- Covalent compounds are formed by the sharing of electrons between atoms.

- Carbon dioxide is covalent because it is formed by the sharing of electrons between carbon and oxygen atoms.

- Good conductors of heat and electricity

- Malleable and ductile

- High melting and boiling points

- Shiny

- 32 (2 × 16)

- Oxide A: Empirical formula: CuO

- Oxide B: Empirical formula: Cu2O

- 0.265 mol

b) Acid-base reaction

- Definition: Isotopes are atoms of the same element that have the same number of protons and electrons but different numbers of neutrons.

- Differences: Isotopes have the same atomic number but different mass numbers.

- Examples:

- Carbon-12 and carbon-14: Used in carbon dating to determine the age of objects

- Uranium-235 and uranium-238: Used in nuclear energy and nuclear weapons