$I=0,k=6\mathrm{.}50{10}^{9}d{m}^{3}mo{l}^{-1}{s}^{-1}$

$I=0\mathrm{.}9M,k=6\mathrm{.}35{10}^{9}d{m}^{3}mo{l}^{-1}{s}^{-1}$When the subatomic species muonium $($Mu$)$ was first discovered in $1960,$ it was not known whether it bore an electric charge. The answer was provided by a kinetic study of the ionic strength effect on the reaction Mu $+$ Cu$2+$ in aqueous solution. The following rate constants were measured at two ionic strengths:

$\backslash (\backslash$begin$\{$array$\}\{$ll$\}$I$=0$ & k$=6\mathrm{.}50\backslash$times $10^\{9\}\backslash$mathrm$\{$dm$\}^\{3\}\backslash$mathrm$\{$~mol$\}^\{-1\}\backslash$mathrm$\{$~s$\}^\{-1\}\backslash \backslash$ I$=0\mathrm{.}9$ M & k$=6\mathrm{.}35\backslash$times

Suppose that muonium had a single negative charge; what would k be expected to be at an ionic strength of $0\mathrm{.}9$ M$?$ What do you deduce about the actual charge on muonium?