<span>A means of solving a problem or dealing with a difficult situation.
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The producers of an ecosystem make energy available to all the other living parts of an ecosystems. Consumers like humans eat the food that producers like plants made decomposers decompose dead plants and animals when they die like bacteria is a decomposer
Answer:
21. Erosion causes physical changes. For example - Land degradation, deforestation.
20. B statement is closely related to climate.
hope it helps!
Answer:
The correct order of increasing reactivity toward nucleophilic acyl substitution is E < D < C < A < F < B.
Explanation:
The stability of the leaving group best determines the manner of reactivity of carboxylates to nucleophilic substitution after the substitution of the nucleophile to the leaving group. The leaving group should, therefore, be protonated with hydrogen ion in the solution to form a stable molecule. From the given list: The leaving group for A, Ethyl thioacetate will be ethanethiol. For B, Acetyl chloride will be Hydrochloric acid. For C, Sodium acetate will be Sodium Hydroxide. For D, Ethyl acetate will be Ethanol. For E, Acetamide will be Ammonia, and for F, Acetic anhydride will be Ethanoic acid. The reactivity of the substitution reaction is dependent on the stability of these leaving groups. The stability of these leaving groups depends on their pKa, and the more the pKa, the lesser the acidity of the leaving group, and the lower the reactivity. Therefore, considering their pKa: A is 8.5, B is -7, C is 13.8, D is 15.9, E is 36, and F is 4.8. When we rearrange this pKa in descending order, we have E, D. C, A, F, B. Which is also the increased reactivity of the nucleophilic acyl substitution.
it small because that bond is not very polar notice that all of those arrows they cancel. because they point in opposite directions. that's why BH 3 is nonpolar if we were to draw the Lewis structure of bf3. ... so even though the boron fluorine bond is polar the molecule as a whole is nonpolar.