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May 5, 2016

# Homework Help: Chemistry

Posted by Zacky on Wednesday, May 12, 2010 at 5:48am.

(1) Why are fractional coefficients permitted in a balanced thermochemical equation?

In thermochemical reactions, only small amounts of matter are considered.

If fractional coefficients were not used, the scale of the reaction would be excessively large.

Fractional coefficients are permitted because the enthalpy change for the reaction is dependent on the amount of matter present.

Fractional coefficients are permitted in order to have the smallest possible set of coefficients for a given reaction.

Fractional coefficients are permitted because the enthalpy change for the reaction is independent of the amount of matter present.

If a thermochemical equation has a coefficient of 1/2 for a formula, it signifies that----?-------.

(2) A body of water with a mass of 732 g changed in temperature from 24.62 to 19.47 °C (Its specific heat is 4.184 J·g-1·K-1).

What would have to be done to cause such a change ? ------?---

How much energy (in kilojoules) is involved in this change?
----?-----kJ
• Chemistry - DrBob222, Wednesday, May 12, 2010 at 11:00am

(1) Why are fractional coefficients permitted in a balanced thermochemical equation?

In thermochemical reactions, only small amounts of matter are considered.

If fractional coefficients were not used, the scale of the reaction would be excessively large.

Fractional coefficients are permitted because the enthalpy change for the reaction is dependent on the amount of matter present.

Fractional coefficients are permitted in order to have the smallest possible set of coefficients for a given reaction. I think this is the one you want.

Fractional coefficients are permitted because the enthalpy change for the reaction is independent of the amount of matter present.

If a thermochemical equation has a coefficient of 1/2 for a formula, it signifies that----?-------.

(2) A body of water with a mass of 732 g changed in temperature from 24.62 to 19.47 °C (Its specific heat is 4.184 J·g-1·K-1).

What would have to be done to cause such a change ? ------?---

How much energy (in kilojoules) is involved in this change?
----?-----kJ
I would need to be cooled but that may be obvious
Second part:
mass x specific heat x delta T = q.

• Chemistry - DrBob222, Wednesday, May 12, 2010 at 11:00am

It would need .....