11.8.3 Can you answer these questions?

11.8.3.1 Arrow not appearing correctly

https://tex.stackexchange.com/landing/r/digest?cta=question&id=736218

When trying to present the results of a reaction, I don't understand why the arrow doesn't appear correctly: 
\documentclass{article} 
\usepackage[modules={all}]{chemmacros} 
\usepackage{chemfig} 
\... 
[chemfig] [chemmacros]
 

asked by Nicolas https://tex.stackexchange.com/landing/r/digest?cta=user&id=231550 Score of 3

11.8.3.2 Letterspacing resets \Umathquad

https://tex.stackexchange.com/landing/r/digest?cta=question&id=736394

The following MWE is to be compiled with LuaLaTeX: 
\documentclass{scrartcl} 
\usepackage{unicode-math} 
\usepackage{microtype} 
\begin{document} 
\Umathquad\textstyle=.3em 
$\langle a,b\rangle = 0$ 
... 
[luatex] [unicode-math] [microtype] [letterspacing]
 

asked by FKranhold https://tex.stackexchange.com/landing/r/digest?cta=user&id=70834 Score of 4

11.8.3.3 Drawing dashed curves with tikz

https://tex.stackexchange.com/landing/r/digest?cta=question&id=736286

I'm trying to draw these pictures with tikz, but I'm having some trouble with these two curves. 
\documentclass{article} 
\usepackage{tikz} 
\usepackage{amsmath} 
\usetikzlibrary{angles, quotes} 
\begin{... 
[tikz-pgf] [vector] [curves]
 

asked by Ismael Joaquim https://tex.stackexchange.com/landing/r/digest?cta=user&id=375141 Score of 1

answered by MS-SPO https://tex.stackexchange.com/landing/r/digest?cta=user&id=245790 Score of 0