In this Thread (https://tex.stackexchange.com/a/301036/229635) it was explained how to make the small vertical lines between two cells disappear by using tabularx and \columncolor and changing the overhang parameters within a multicolumn.
Now I am looking for a way how to create a Table like shown in the picture attached to this post.
The reason why I am asking for your help is that the code updated on August 7th 2020 by Bernard (see link above) doesn't create a table fitting to the text width of my document.
In other words: Is there a way to get rid of all the absolute values and the multicolumn used in the m{} parameters so that the table fits still the textwidth no matter how many columns the table has while still implementing the overhang parameter for color fill to avoid the thin white lines between the cells? I Want to create a Table having no gridlines and a light gray head row without the small vertical lines between color filled cells while using \cellcolor.
Thanks a lot in advance, Benson_G
Picture Reference: Worm, M.; Leibig, D.; Dingels, C.; Frey, H. Cleavable Polyethylene Glycol: 3,4-Epoxy-1-butene as a Comonomer to Establish Degradability at Physiologically Relevant pH.ACS Macro Letters2016,5(12), 1357–1363
\documentclass[a4paper,10pt, enabledeprecatedfontcommands]{scrartcl} %Art des Dokuments, Schriftgröße etc.
\usepackage[utf8]{inputenc}%Direkte Angabe von Umlauten möglich
\usepackage[left=3cm,right=2cm,top=2cm,bottom=2cm,includehead]{geometry}%Maße für die wissenschaftliche Arbeit
\usepackage[parfill]{parskip} %Bessere Seitenumbrüche
\usepackage[onehalfspacing]{setspace} %Zeilenabstand
\usepackage[T1]{fontenc} %Silbentrennung
\usepackage[english]{babel} %Sprachanpassungen
\usepackage{graphicx} %Einfügen von Bildern
\usepackage{tabularx} %Tabellen
\usepackage{booktabs} %Weitere Möglichkeiten für Tabellen
\usepackage{here} %Lage von Tabellen und Bildern
\usepackage{units}
\usepackage{physics}
\usepackage{amsmath}
\usepackage{textgreek}
\usepackage{textcomp}
\usepackage{amssymb}
\usepackage[labelformat=simple]{subcaption}
\usepackage{float}
\usepackage{pdfpages}
\usepackage{lmodern}
\usepackage{enumitem}
\usepackage[hyphens]{url} %% be sure to specify the option 'hyphens'
% \usepackage[pdftex,bookmarksnumbered,hidelinks,breaklinks]{hyperref}
\usepackage[superscript]{cite}
\usepackage[scaled]{helvet}
\renewcommand\familydefault{\sfdefault}
\usepackage[version=3]{mhchem} %Summenformeln angeben
\usepackage[labelsep=period]{caption}
\usepackage[per-mode = reciprocal, output-decimal-marker={,}, exponent-product = {\cdot}]{siunitx} %Si-Einheiten
% \usepackage[colorlinks,
% pdfpagelabels,
% pdfstartview = FitH,
% bookmarksopen = true,
% bookmarksnumbered = true,
% linkcolor = black,
% plainpages = false,
% hypertexnames = false,
% citecolor = black]{hyperref}
\usepackage{color}
\usepackage{colortbl}
\definecolor{hellgrau}{rgb}{0.90,0.90,0.90}
\newcommand{\RM}[1]{\MakeUppercase{\romannumeral #1{.}}}
\renewcommand\thesubfigure{\thefigure.\arabic{subfigure}}
\addtokomafont{captionlabel}{\bfseries}
\DeclareNewTOC[
type=scheme, % Name der Umgebung
types=schemes, % Erweiterung (\listofschemes)
float, % soll gleiten
floatpos=tbp, % voreingestellte Gleitparameter
name=Scheme, % Name in Überschriften
listname={Verzeichnis der Schemata}, % Listenname
% counterwithin=chapter
]{los}
\begin{document}
\begin{table}[H]
\vspace{-1.8 \baselineskip}
\centering
\setlength\belowcaptionskip{5 pt}
\caption{\textbf{Reaction mixture used for the synthesis of cyclohexanone 4-nitrophenylhydrazone.}}
\begin{tabular}{cccccc}
\cellcolor{hellgrau} chemicals &\cellcolor{hellgrau} \textit{M} $^a$ (g mol$^{\text{-1}}$) &\cellcolor{hellgrau} \textit{n} $^a$(mol 10$^{\text{-4}}$) &\cellcolor{hellgrau} \textit{V} $^a$ (mL) &\cellcolor{hellgrau} \textit{m} $^a$ (g) &\cellcolor{hellgrau} $\varrho$ $^a$ (g mL$^{\text{-1}}$)\\
Cyclohexanone & 98.14 & \multicolumn{4}{c}{0.5 mL of the destillate} \\
4-Nitrophenyl hydrazine & 153.14 & 26 & - & 0.4 & - \\
Sulfuric acid & 98.08 & 372 & 2 & 3.68 & 1.84 \\
Water & 18.02 & 1664 & 3 & 3 & 1.00 \\
Ethanol & 47.07 & 1678 & 10 & 7.9 & 0.79 \\
\end{tabular}
\vspace{0.6 \baselineskip} \\
\raggedright
$^a$Molecular mass \textit{M}, amount of substance \textit{n}, volume \textit{V}, mass \textit{m}, density $\varrho$.
\label{tab:ReactionMixtureCyclohexanone4-nitrophenylhydrazone}%
\vspace{-1.8 \baselineskip}
\end{table}
\end{document}