Chemistry, 05.11.2019 05:31, litwork5885

Given the reactions
a.) n2(g)+o2(> 2no(g) delta h= -180.5
b.) n2(g) + 3h2(g) ——> 2nh3(g) delta h= -91.8
c.)2h2(g)+ o2(g) —-> 2h2o(g) delta h= -486.6

what is the delta h for the reaction below
4nh3(g)+5o2(> 4no(g)+6h2o(g)

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answered: dilly1190

The answer to your question is: ΔH = 1637.8

Explanation:

Hess' law: This law states that the enthalpy change can be calculated even if it is not calculated directly.

"if a chemical change takes place by several routes, the overall enthalpy change is the same regardless the route".

Process

A) N2(g)+O2(g)—->2NO(g) Δ H= -180.5

B) N2(g) + 3H2(g) ——> 2NH3(g) Δ H= -91.8

C)2H2(g)+ O2(g) —-> 2H2O(g) Δ H= -486.6

The result must be:

4NH3(g)+5O2(g)—->4NO(g)+6H2O(g)

Turn letter B and multiply it by 2

4NH3 ⇒ 2N2 + 6H2 ΔH = 183.6

Multiply letter A by 2

2N2 + 2O2 ⇒ 4 NO ΔH = -361

Multiply letter C by 3

6H2 + 3O2 ⇒ 6H2O ΔH = -1459.8

Finally we add the equations up and simplify then:

4NH3 + 5O2 ⇒ 4NO + 6 H2O

And we add the ΔH = 183.6 - 361 - 1459.8

= -1637.8

answered: Guest

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.

answered: Guest

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.

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Given the reactions
a.) n2(g)+o2(> 2no(g) delta h= -180.5
b.) n2(g) + 3h2(g) ——>...