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makvit [3.9K]
3 years ago
15

A sample of metal is heated until it melts and begins to glow red. When it cools, it appears the same color as it did before it

was heated. This is evidence that a chemical reaction occurred. is it true or false
Chemistry
1 answer:
frosja888 [35]3 years ago
8 0

Answer:

Explanation:

trueeeeeeeeeeeeeeeeeeeeeeeeeee

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Answer:

It’s twice as much as 9+10

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Describe how oxidation and reduction involve electrons, change oxidation numbers, and combine in
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Redox

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For a process Arightwards harpoon over leftwards harpoonB, at 25 °C there is 10% of A at equilibrium while at 75 °C, there is 80
Lostsunrise [7]

This question is describing the following chemical reaction at equilibrium:

A\rightleftharpoons B

And provides the relative amounts of both A and B at 25 °C and 75 °C, this means the equilibrium expressions and equilibrium constants can be written as:

K_1=\frac{90\%}{10\%}=9\\\\K_2=\frac{20\%}{80\%}  =0.25

Thus, by recalling the Van't Hoff's equation, we can write:

ln(K_2/K_1)=-\frac{\Delta H}{R}(\frac{1}{T_2} -\frac{1}{T_1} )

Hence, we solve for the enthalpy change as follows:

\Delta H=\frac{-R*ln(K_2/K_1)}{(\frac{1}{T_2} -\frac{1}{T_1} ) }

Finally, we plug in the numbers to obtain:

\Delta H=\frac{-8.314\frac{J}{mol*K} *ln(0.25/9)}{[\frac{1}{(75+273.15)K} -\frac{1}{(25+273.15)K} ] } \\\\\\\Delta H=4,785.1\frac{J}{mol}

Learn more:

  • brainly.com/question/10038290
  • brainly.com/question/19671384
5 0
3 years ago
In the reaction shown above , the?
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Answer:

I think option (d) is right answer

8 0
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Which of the following best defines balanced forces?
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Balanced forces are forces that act in opposite directions and cancel each other out

let me know if you have any other questions

6 0
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