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Give answer! - Thermodynamics - NEET-2

Three thermochemical equations are given below

(i) C_{\left ( graphite \right )}+O_{2}\left ( g \right )\rightarrow CO_{2}\left ( g \right );

                                                             \Delta _{r} H^{o}=xkJmol^{-1}

(ii) C_{\left ( graphite \right )}+\frac{1}{2}O_{2}\left ( g \right )\rightarrow CO\left ( g \right );

                                                               \Delta _{r} H^{o}=ykJmol^{-1}

(iii) CO\left ( g \right )\frac{1}{2}O_{2}\left ( g \right )\rightarrow CO_{2}\left ( g \right );

                                                          \Delta _{r} H^{o}=zkJmol^{-1}

Based on the above equations, find out which of the relationship given below is correct?

  • Option 1)

    x=y-z

  • Option 2)

    z=x+y

  • Option 3)

    x=y+z

  • Option 4)

    y=2z-x

 
Answers (1)
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As we learnt in

Hess's Law -

The total amount of heat change in a chemical reaction is the same whether the reaction is carried  out in one or several steps by one or more methods.

- wherein

C_{(s)}+O_{2(g)}\rightarrow CO_{2(g)}

\Delta H= 393.5\, kj

C_{(s)}+\frac{1}{2}O_{2(g)}\rightarrow CO_{(g)}

\Delta H_{1}= 110.5\, kj

CO_{(g)}+\frac{1}{2}O_{2(g)}\rightarrow CO_{2(g)}

\Delta H_{2}= 283.0\, kj

\Delta H= \Delta H_{1}+\Delta H_{2}

 

 According to Hest law, equation 

(i) is sum of equation (ii) and (iii)

 


Option 1)

x=y-z

This option is incorrect 

Option 2)

z=x+y

This option is incorrect 

Option 3)

x=y+z

This option is correct 

Option 4)

y=2z-x

This option is incorrect 

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