Which statement is correct about the Group 1 elements?
A The Cs⁺ ion has a more negative enthalpy of hydration than the Rb⁺ ion - AQA - A-Level Chemistry - Question 17 - 2022 - Paper 3
Question 17
Which statement is correct about the Group 1 elements?
A The Cs⁺ ion has a more negative enthalpy of hydration than the Rb⁺ ion.
B The enthalpy of atomisation for ... show full transcript
Worked Solution & Example Answer:Which statement is correct about the Group 1 elements?
A The Cs⁺ ion has a more negative enthalpy of hydration than the Rb⁺ ion - AQA - A-Level Chemistry - Question 17 - 2022 - Paper 3
Step 1
A The Cs⁺ ion has a more negative enthalpy of hydration than the Rb⁺ ion.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
This statement is incorrect. The enthalpy of hydration becomes more negative as ionic radius decreases, meaning that Cs⁺, being larger than Rb⁺, would not have a more negative enthalpy.
Step 2
B The enthalpy of atomisation for potassium is greater than the enthalpy of atomisation for sodium.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
This statement is also incorrect. Generally, the enthalpy of atomisation increases down the group; however, potassium's enthalpy of atomisation is lower than that of sodium due to its larger atomic size.
Step 3
C The melting point of potassium is higher than the melting point of sodium.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
This statement is incorrect. Sodium has a higher melting point than potassium, following the trend in group 1 elements where melting points decrease down the group.
Step 4
D The second ionisation energy of rubidium is lower than the second ionisation energy of lithium.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
This statement is correct. The second ionisation energy of rubidium is indeed lower than that of lithium due to the larger atomic radius and the increased shielding effect in rubidium.
