Could please someone help me with this problem?

Question

Na2CO3 = Na2CO3 . 5H2O What is the enthalpy change of this reaction called?

Answer 1

The reaction you listed in not balanced....there is no water on the "left", how can it appear on the "right".

If the change in enthalpy of a reaction is negative, the reaction is called "exothermic".
If the change in enthalpy of a reaction is positive, the reaction is called "endothermic".

In order to determine whether the reaction is endo/exo thermic, you need to determine the (delta H) value of the reaction....something which might be hard to look up in this case, the difference between the hydrated crystals and the anhydrous Na2CO3. But there is another way.

A reaction is spontaneous (proceeds on its own without added energy) is there is a negative change in the Gibbs free energy (delta G).
The change in the Gibbs free energy is given as,
(delta G) = (delta H) - (delta S) * T
where (delta S) is the change in the entropy of the reaction, and T is the temperature.
W can assume that the hydration process is spontaneous I would think, so the (delta G) value would be negative.
By looking at the reaction, we can make the guess that entropy is being reduced in the reaction since water molecules are being pulled out of the air and getting "trapped" in the crystals. So lets assume (delta S) to be negative. And the reaction is proceeding at some positive temperature on the Kelvin scale.

So if we re-write the (delta G) equation with + or - signs,
(-) = (delta H) - (-)(+)
well, a (-) * (+) is still negative, but since you are subtracting it, it has the effect of adding the opposite value, so it becomes,
(-) = (delta H) + (+)
so the only way for (delta G) to be negative would be if the value of (delta H) is negative and has a greater magnitude than the product of (delta S) and T.

So if (delta H) is negative, then the process is exothermic.
*Assuming that my assumptions about the signs of (delta S) and (delta G) were correct.

Answer 2

It is called the heat of crystallization,the 5H2O is the water of crystallization.

Answer 3

ok it helps if you have a balanced equation. i'm not gonna look it up for you. open the CRC and figure it out yourself.

the crystal is getting hydrated, but it's done wrong.

Answer 4

you can dissolve your salt in water and find out if by measuring temperature change,, if its getting cold and the temperature low its endo and if its getting hot and the temperature high its exo.and i think its endothermic

Answer 5

write the question clearly