Photo AI
Lithium is a metal found in Group 1 of the Periodic Table - OCR Gateway - GCSE Chemistry - Question 22 - 2019 - Paper 1
Question 22
Lithium is a metal found in Group 1 of the Periodic Table. (i) Describe the structure and bonding in a metal. You may include a diagram in your answer. (ii) Lithi... show full transcript
Worked Solution & Example Answer:Lithium is a metal found in Group 1 of the Periodic Table - OCR Gateway - GCSE Chemistry - Question 22 - 2019 - Paper 1
Step 1
Describe the structure and bonding in a metal.
Answer
Metals are characterized by a structure consisting of closely packed atoms arranged in a lattice. The atoms are held together by metallic bonds, which result from the electrostatic attraction between positively charged metal ions and a sea of delocalized electrons. This delocalization allows electrons to move freely, contributing to properties such as conductivity and malleability. A diagram can illustrate this structure, showing metal cations surrounded by a sea of electrons.
Step 2
Explain why metals are malleable.
Answer
Metals are malleable because the layers of ions within the metallic lattice can slide over one another without breaking the metallic bonds. Even though these bonds are strong, the delocalized electrons allow the metal structure to distort when force is applied, making the metal capable of being shaped into different forms.
Step 3
Explain why metals can conduct electricity.
Answer
Metals can conduct electricity because of the presence of free-moving delocalized electrons. When a potential difference is applied, these electrons can easily flow through the metallic structure, transferring electrical energy. In both solid and liquid states, the ability of the electrons to move is key to the conduction process.
Step 4
A scientist thinks that alloy C is best for making an aircraft. Is she correct? Explain your answer using evidence from the table.
Answer
To assess if alloy C is the best choice for aircraft, we can consider its properties in comparison to alloys A and B. Alloy C has a strength of 565 MPa, which is less than alloy A (550 MPa) but more than alloy B (555 MPa). However, alloy C also has a higher melting point (655 °C) compared to alloy B (580 °C) and lower density (2.55 g/cm³). Therefore, alloy C is not definitively the best choice based solely on strength and density. Alloy A, with the highest strength and melting point, could be considered more suitable depending on the specific requirements for aircraft construction.
Step 5
Calculate the percentage of lithium atoms in the diagram of alloy B.
Answer
To find the percentage of lithium atoms in the diagram of alloy B, count the total number of atoms represented in the diagram. Assume there are 10 total atoms, with 2 being lithium. The percentage of lithium atoms can be calculated using the formula: [ \text{Percentage of Lithium} = \left( \frac{\text{Number of Lithium Atoms}}{\text{Total Number of Atoms}} \right) \times 100% ] Substituting the values gives: [ \text{Percentage of Lithium} = \left( \frac{2}{10} \right) \times 100% = 20% ]
Step 6
Use your answer to part (c)(i) to explain if the diagram accurately shows the structure of alloy B.
Answer
If the calculated percentage of lithium atoms is 20% and the diagram shows 2 out of 10 atoms as lithium, then it accurately represents the composition of alloy B. This suggests a proper ratio that reflects the actual percentage of lithium in the alloy. However, if the total number of atoms in the diagram deviates significantly from the expected proportion of lithium to aluminium, then the diagram may not accurately display the structure.