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This question is about atoms, molecules and nanoparticles - AQA - GCSE Chemistry - Question 3 - 2016 - Paper 2
Question 3
This question is about atoms, molecules and nanoparticles. 3 (a) Different atoms have different numbers of sub-atomic particles. 3 (a) (i) An oxygen atom can be re... show full transcript
Worked Solution & Example Answer:This question is about atoms, molecules and nanoparticles - AQA - GCSE Chemistry - Question 3 - 2016 - Paper 2
Step 1
Explain why the mass number of this atom is 16.
Answer
The mass number of an atom is defined as the total number of protons and neutrons in its nucleus. For the oxygen atom represented as (^{16}_{8}O), it has 8 protons and 8 neutrons. Therefore, the mass number is calculated as:
This means that the mass number is indeed 16 due to the combination of these sub-atomic particles.
Step 2
Explain why \(^{12}_{6}C\) and \(^{14}_{6}C\) are isotopes of carbon.
Answer
Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. Both (^{12}{6}C) and (^{14}{6}C) have 6 protons, which gives them the same atomic number and identity as carbon. However, (^{12}{6}C) has 6 neutrons, while (^{14}{6}C) has 8 neutrons, leading to different mass numbers.
Step 3
Complete Figure 3 to show the arrangement of the outer shell electrons of the hydrogen and oxygen atoms in a molecule of water.
Answer
In a water molecule, each hydrogen atom has 1 electron and the oxygen atom has 6 electrons in its outer shell. Using dots (•) to represent the electrons, the arrangement would appear as follows:
••
H O H
••
Each hydrogen shares its electron with oxygen, resulting in two bonding pairs and the overall structure of the molecule.
Step 4
Step 5
Why does pure water not conduct electricity?
Answer
Pure water does not conduct electricity because it lacks free ions and electrons. Electrical conductivity in a solution generally occurs due to the presence of charged particles, but in pure water, there are no ions available to facilitate the flow of electricity.
Step 6
How does the size of a nanoparticle compare with the size of an atom?
Answer
Nanoparticles are significantly larger than individual atoms. While an atom typically measures in picometers (1 picometer = 10^{-12} meters), nanoparticles can range from a few nanometers (1 nanometer = 10^{-9} meters) to several hundred nanometers in size. Thus, nanoparticles can consist of hundreds to thousands of atoms.
Step 7
Suggest one reason why 1 g of cobalt oxide nanoparticles is a better catalyst than 1 g of cobalt oxide powder.
Answer
One reason is that cobalt oxide nanoparticles have a larger surface area compared to cobalt oxide powder. The increased surface area allows for more active sites for catalytic reactions, enhancing the efficiency and speed of the reaction.