Question

the percent by mass of copper(ii) in cu(no2)2 is %.

Explanation:

Step1: Calculate molar masses

The molar mass of Cu is $M_{Cu}=63.55\ g/mol$. The molar mass of $N$ is $M_N = 14.01\ g/mol$, the molar mass of $O$ is $M_O=16.00\ g/mol$. For $Cu(NO_2)_2$, the molar - mass $M$ is calculated as follows:

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Step2: Calculate mass - percent of Cu

The mass - percent of Cu in $Cu(NO_2)_2$ is given by the formula $\text{Mass}\%=\frac{\text{Mass of Cu in compound}}{\text{Molar mass of compound}}\times100\%$.

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Answer:

$40.85$