Enthalpy of Hydration: Cs vs Li

  • Thread starter broegger
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In summary: Li or Cs are placed in contact with water, there is a redox reaction that results in release of energy.
  • #1
broegger
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Hi.

How come that Cs reacts more violently with water than Li, when the enthalpy of hydration for Li is -520 kJ/mol while it is only -276 kJ/mol for Cs. More energy is released in the Li reaction, but still it reacts more quietly?

(EDIT: Oops, maybe this should be in the homework section?)
 
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  • #2
What else affects the reaction? It ain't ALL enthalpy of hydration.
 
  • #3
Yes, for instance, consider the radii of the elements.
 
  • #4
There will occur a redoxreaction when Li and Cs are put in water. What happens in this reaction with Li and Cs in this redoxreaction ? In combination to the previous post it should answer your question.
 
  • #5
The Li atoms are smaller, but how does that affect the reaction?
 
  • #6
broegger said:
The Li atoms are smaller, but how does that affect the reaction?

compare:

Li --> Li(+) + e(-) and Cs --> Cs(+) + e(-)

in what electron lies more energy ? and what electron is easiest being lost ?
 
  • #7
How on Earth do you spec an enthalpy of hydration for an atomic species (like Li or Cs)? What does that even mean? Would you (the OP) please define the enthalpy of hydration in this context?

Secondly, translate the words "violently" and "quietly" into terms involving well-defined physical quantites. The answer will pop right out.
 
  • #8
I have no idea, just quoting from the book, basically. Doesn't Li- and Cs-solids exist? I'm a lousy chemist, I know.

I would think that "quietly" means slow and "violently" means fast, so the statement is that the reaction rate of Cs + water is larger than the reaction rate of Li + water. I understand that the reaction rate is influenced by other factors than the difference in enthalpy...
 
  • #9
Okay --- step at a time: what's the first thing that happens when elemental Li or Cs are placed in contact with water? (Yes, they're both solids.)
 
Last edited:
  • #10
Gokul43201 said:
How on Earth do you spec an enthalpy of hydration for an atomic species (like Li or Cs)? What does that even mean? Would you (the OP) please define the enthalpy of hydration in this context?

Secondly, translate the words "violently" and "quietly" into terms involving well-defined physical quantites. The answer will pop right out.

the topic starter said: 'reacts more violently with water'

--> thus we speak about the reaction between elemental Li /Cs and water, i assume.
 

1. What is enthalpy of hydration?

Enthalpy of hydration refers to the energy released or absorbed when a substance dissolves in water. It is a measure of the strength of the interaction between the solute and water molecules.

2. How is enthalpy of hydration different for cesium (Cs) and lithium (Li)?

The enthalpy of hydration for cesium is much higher than that of lithium. This is because cesium ions are larger and have a weaker charge compared to lithium ions, allowing for stronger interactions with water molecules.

3. Does enthalpy of hydration affect the solubility of cesium and lithium?

Yes, the enthalpy of hydration can affect the solubility of these elements. Since cesium has a higher enthalpy of hydration, it is more soluble in water compared to lithium.

4. Can enthalpy of hydration be measured experimentally?

Yes, enthalpy of hydration can be measured experimentally using calorimetry. This involves measuring the change in temperature when a known amount of the substance dissolves in water.

5. How does enthalpy of hydration impact the properties of cesium and lithium compounds?

The higher enthalpy of hydration for cesium makes its compounds more soluble and have stronger interactions with water. This can affect properties such as melting and boiling points, as well as the overall stability of the compounds.

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