Thermodynamics ...

What can be used in combination with a calorimeter to compare the specific heats of two substances?

Statement 1: The $$\Delta H_{reaction}$$ of a particular reaction can be arrived at by the summation of the $$\Delta H_{reaction}$$ values of two or more reactions that, added together, will give the $$\Delta H_{reaction}$$ of the particular reaction.
Statement 2: Hess's Law conforms to the First Law of Thermodynamics, which states that the total energy of the universe is a constant.

The heat of formation of $$CO(g)$$ and $$CO_2(g)$$ are $$\Delta H=-110$$ and $$\Delta H=-393kJmmol^{-1}$$ respectively. What is the heat of reaction$$(\Delta H)$$ (in kJ $$mol^{-1}$$) for the following reaction?
$$CO(g)+\displaystyle\frac{1}{2}O_2(g)\rightarrow CO_2(g)$$

The spontaneity of a reaction is indicated by:

The reverse of a spontaneous reaction is ......... .

What is the necessary condition for the sponataneity of a process?

The important considerations in deciding if a reaction will be spontaneous are :

What is the value of $$\Delta H$$ for the reaction $$X + 2Y \rightarrow 2Z$$?
$$ W+X\rightarrow  2Y$$ ;                                  $$\Delta H=-  400 $$ kcal/mol
$$ 2W + 3X \rightarrow  2Z + 2Y$$  ;                  $$\Delta H=- 150 $$ kcal/mol