According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

The given final reaction is,

$4Al(s)+3MnO_2(s)\rightarrow 2Al_2O_3(s)+3Mn(s)$ $\Delta H=?$

The intermediate balanced chemical reaction will be,

(1) $2Al(s)+\frac{3}{2}O_2(g)\rightarrow Al_2O_3(s)$ $\Delta H_1=-1680kJ/mole$

(2) $Mn(s)+O_2(g)\rightarrow MnO_2(s)$ $\Delta H_2=-520kJ/mole$

First we will multiply reaction 1 by 2 and reverse reaction of reaction 2 by 3 then adding both the equation, we get :

The expression for final enthalpy is,

$\Delta H=[n\times \Delta H_1]+[n\times (-\Delta H_2)]$

where,

n = number of moles

$\Delta H=[2mole\times (-1680kJ/mole)]+[3\times -(-520kJ/mole)]$

$\Delta H=-1800kJ$

Therefore, the enthalpy change of reaction is -1800 kJ

8 0

3 years ago

In our simulation what did the σ (sigma) stand for?

soldier1979 [14.2K]

Answer:

C -The atomic radius

Explanation:

I took the test :)

6 0

3 years ago

Sodium hydroxide is added to many swimming pools to neutralize excess acidity from hydrochloric acid (which is a solution of hyd

Gnom [1K]

Hope this helps you!

7 0

3 years ago

The density of no2 in a 4.50 l tank at 760.0 torr and 25.0 Â°c is ________ g/l.

kap26 [50]

From ideal gas equation that is PV=nRT
n(number of moles)=PV/RT
P=760 torr
V=4.50L
R(gas constant =62.363667torr/l/mol
T=273 +273=298k
n is therefore (760torr x4.50L) /62.36367 torr/L/mol x298k =0.184moles
the molar mass of NO2 is 46 therefore density= 0.184 x 46=8.464g/l

7 0

3 years ago

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