Answer:
ESCALAS MAYORES (D, E, G, A, B) Porfavor necesito ayuda,te lo agradecería muchísimo!!
Es urgente 
 
        
             
        
        
        
 Answer:
8. the answer is B.
9. the answer is A.
Explanation:
Hello!
8. In this case, by bearing to mind that the limiting reactant is always completely consumed and the excess one remain as a leftover at the end of the reaction, we can also infer that as all the limiting reactant is consumed, it must determine the maximum amount of product as the excess reactant will hypothetically produce a greater mass than expected; thus, the answer to this question is B.
9. In this case, since the mole ratio of oxygen to water is 1:2, the following proportional factor is used to calculate the produced mass of water:

Thus, the answer is this case is A.
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Answer;
(3) Substance A is an element and substance Z is a compound.
Explanation; 
-A compound is a substance formed when two or more chemical elements are chemically bonded together, such as water, carbon dioxide, methane, etc while an element is a pure chemical substance made of same type of atoms, such includes, oxygen, potassium, hydrogen, carbon, etc. 
- Compounds can be broken
down or decomposed into simpler substances: elements cannot be broken down chemically into simpler substances . 
 
        
                    
             
        
        
        
TMS stands for Tetramethylsilane 
Formula : Si(CH₃)₄
It is used as internal standard for chemical shift
In TMS all the four methyl groups are similar thus all the 12 hydrogen are chemically equivalent. They will show proton NMR at same level and which will appear as a singlet.
We have defined this singlet to be as reference set as zero. 
Generally the other organic compounds show chemical shift downfield.So have positive chemical shift with respect to TMS shift.