Write equations to represent the following processes. The standard enthalpy of f

Question

Write equations to represent the following processes. The standard enthalpy of formation of CH_3Br_(I) The standard enthalpy of formation of CH_3COC_2H_5(I) The standard enthalpy of formation of NaNO_3(s) All elements are assigned a value for enthalpy of formation equal to zero. Why? Standard Enthalpy of Combustion (delta H_C degree) Standard Enthalpy of Combustion is defined as the enthalpy change when one mole of a substance is completely burned in oxygen (since energy is usually released in such a reaction delta H_c will usually be negative). For example, delta H_c [C_2 H_6(g)] = -1565 kJmol^-1 means that when the reaction below is carried out, 1565 kJ of energy are released. C_2H_6(g) + 3 1/2 O_2(g) rightarrow 2CO_2(g) + 3H_2 O_(I) delta H degree = -1565 kJmol^-1

Explanation / Answer

Q1.

CH3Br = Carbon, Hydrogen, Bromine

so..

C(s) and H2(g), and Br2(l)

C(s) + H2(g) + Br2(l) = CH3Br(l)

balance

C(s) + 3/2H2(g) + 1/2Br2(l) = CH3Br(l)

Q2.

CH3COC2H5(l) ... C H and O

so

4C(s) + 1/2O2(g) + 4H2(g) = CH3COC2H5(l)

Q3.

NaNO3 = Na and N, O

Na(s) N2(g) and O2(g)

so

Na(s) + 1/2N2(g) + 3/2O2(g) = NaNO3 (s)

Q4.

Because it is an easy reference to get, elemental material... also it is pretty common in earth so it is easier

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