This is called bond energy, or bond enthalpy, and is measured in units of kilojoules per mole (kJ/mol).
Answer:
Explanation:
1:faringe:es un conducto que permite la comunicación entre las fosas nasales (el paso del aire por la nasofaringe a la laringe) y la cavidad bucal
Laringe:es una cavidad formada por cartílagos que presenta una saliente comúnmente llamada "nuez" en la laringe se encuentra las cuerdas vocales que al vibrar con el aire produce la voz
Tráquea:es un conducto de doce centímetros de longitud,situado delante del estómago.la tráquea brinda una vía abierta al aire que entra y sale se los pulmones
18. c
19. A
20. decomposition reaction
21. 4
22. 0.04%
Answer:
Explanation:
All three lighter boron trihalides, BX3 (X = F, Cl, Br), form stable adducts with common Lewis bases. Their relative Lewis acidities can be evaluated in terms of the relative exothermicities of the adduct-forming reaction. Such measurements have revealed the following sequence for the Lewis acidity: BF3 < BCl3 < BBr3 (in other words, BBr3 is the strongest Lewis acid).
This trend is commonly attributed to the degree of π-bonding in the planar boron trihalide that would be lost upon pyramidalization (the conversion of the trigonal planar geometry to a tetrahedral one) of the BX3 molecule, which follows this trend: BF3 > BCl3 > BBr3 (that is, BBr3 is the most easily pyramidalized). The criteria for evaluating the relative strength of π-bonding are not clear, however. One suggestion is that the F atom is small compared to the larger Cl and Br atoms, and the lone pair electron in the 2pzorbital of F is readily and easily donated, and overlaps with the empty 2pz orbital of boron. As a result, the [latex]\pi[/latex] donation of F is greater than that of Cl or Br. In an alternative explanation, the low Lewis acidity for BF3 is attributed to the relative weakness of the bond in the adducts F3B-L.
