Answer:
Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen: 2 H2O → 2 H2 + O. Efficient and economical photochemical water splitting would be a technological breakthrough that could underpin a hydrogen economy.
Explanation: 2 H2O → 2 H2 + O.
Answer:
Four possible isomers (1–4) for the natural product essramycin. The structure of compound 1 was attributed to essramycin by 1H NMR, 13C NMR, HMBC, HRMS, and IR experiments.
Explanation:
Three synthetic routes were used to prepare all four compounds (Figure 2A). All three reactions utilize 2-(5-amino-4H-1,2,4-triazol-3-yl)-1-phenylethanone (5) as the precursor, whereas each uses different esters (6–8) to construct the pyrimidinone ring. Isomer 1 was prepared by reaction A, which used triazole 5 and ethyl acetoacetate (6) in acetic acid. This was the reaction used in syntheses of essramycin by the Cooper and Moody laboratories.3,4 Reaction B produced compound 2 (minor product) and compound 3 (major product), which were separated chromatographically. This reaction allowed reagent 5 to react with ethyl 3-ethoxy-2-butenoate (7) in the presence of sodium in methanol, under reflux for 24 h. Compound 4 was prepared by reaction C, which was obtained by reflux of 5 and methyl 2-butynoate (8) in n-butanol.
Answer:

Explanation:
Hello!
In this case, when performing mathematical operations with numbers in scientific notation, the first step is to write them in standard notation:
550 - 65.0
Thus, the result without any significant figures-based analysis is:
615.0
However, since 550 is significant to the ones and 65.0 to the tenths, we need to round the result to the bigger significance, in this case to the ones; therefore the appropriate result would be:
615
That in scientific notation would be:

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