The "Dawn horses" were actually not related to horses! Recent studies of fossils found that "Dawn Horses" were buried in the same rock layers as modern horses! evolutionists were shocked at first but then decided that the "Dawn horse" was related to rabbits! Now to answer your question no one really knows why they went extinct. Evolutionist believe they changed into rabbits and Creationists (people who believe God created the universe and that evolution is incorrect) believe they died out due to climate changes after the global flood of Noah.
C. 18.0g. all you really have to do is add both of them together and you get your answer.
Answer:
100 g
Explanation:
From the question given above, the following data were obtained:
Original amount (N₀) = 400 g
Time (t) = 4 years
Half-life (t½) = 2 years
Amount remaining (N) =?
Next, we shall determine the number of half-lives that has elapse. This can be obtained as follow:
Time (t) = 4 years
Half-life (t½) = 2 years
Number of half-lives (n) =?
n = t / t½
n = 4 / 2
n = 2
Thus, 2 half-lives has elapsed.
Finally, we shall determine the amount remaining of the radioactive isotope. This can be obtained as follow:
Original amount (N₀) = 400 g
Number of half-lives (n) = 2
Amount remaining (N) =?
N = 1/2ⁿ × N₀
N = 1/2² × 400
N = 1/4 × 400
N = 0.25 × 400
N = 100 g
Thus, the amount of the radioactive isotope remaing is the 100 g.
Copper substance cannot be decomposed by a chemical change.
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- When heated, the copper to carbonate breaks down into copper to oxide. The copper carbonate, which is dark in colour, releases carbon dioxide as well.Because they are the simplest chemically, elements cannot be broken down by chemical processes.
- Elements are those pure compounds that cannot be broken down by reactions, heating, electrolysis, or other common chemical processes. Examples of elements are oxygen, gold, and silver. Its makeup stays the same, though. One instance of a physical change is melting. A physical change is when a sample of matter experiences a change in some of its qualities but not in its identity. Water turns into water vapour when it is heated.
Learn more about copper here:
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Answer : The entropy change for the surroundings of the reaction is, -198.3 J/K
Explanation :
We have to calculate the entropy change of reaction 
.
![\Delta S^o=[n_{NH_3}\times \Delta S^0_{(NH_3)}]-[n_{N_2}\times \Delta S^0_{(N_2)}+n_{H_2}\times \Delta S^0_{(H_2)}]](https://tex.z-dn.net/?f=%5CDelta%20S%5Eo%3D%5Bn_%7BNH_3%7D%5Ctimes%20%5CDelta%20S%5E0_%7B%28NH_3%29%7D%5D-%5Bn_%7BN_2%7D%5Ctimes%20%5CDelta%20S%5E0_%7B%28N_2%29%7D%2Bn_%7BH_2%7D%5Ctimes%20%5CDelta%20S%5E0_%7B%28H_2%29%7D%5D)
where,
= entropy of reaction = ?
n = number of moles
= standard entropy of 
= standard entropy of 
= standard entropy of 
Now put all the given values in this expression, we get:
![\Delta S^o=[2mole\times (192.5J/K.mole)]-[1mole\times (191.5J/K.mole)+3mole\times (130.6J/K.mole)]](https://tex.z-dn.net/?f=%5CDelta%20S%5Eo%3D%5B2mole%5Ctimes%20%28192.5J%2FK.mole%29%5D-%5B1mole%5Ctimes%20%28191.5J%2FK.mole%29%2B3mole%5Ctimes%20%28130.6J%2FK.mole%29%5D)
Therefore, the entropy change for the surroundings of the reaction is, -198.3 J/K
