The table shows the standard enthalpy of formation, ΔfHθ, for some of the substances in the reaction C2H6(g) + 6F2(g) ⟶ C2F6(g) + 6HF(g) ΔHθ = −2898 kJ mol−1

​ΔfHθ /kJ mol−1
C2H6(g) −84
C2F6(g) −1344
What is the standard enthalpy of formation, in kJ mol−1, for HF(g)?

Answer is in а phоtо. I cаn оnly uplоаd it to a file hоsting sеrvice. link bеlow!

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"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

i'm pretty sure its b i might be wrong though!