**Step 1. **Mass of C in the first sample

$\begin{array}{rcl}{\mathbf{m}}_{\mathbf{HCN}}& \mathbf{=}& {\mathbf{m}}_{\mathbf{H}}\mathbf{+}{\mathbf{m}}_{\mathbf{C}}\mathbf{+}{\mathbf{m}}_{\mathbf{N}}\\ {\mathbf{m}}_{\mathbf{C}}& \mathbf{=}& {\mathbf{m}}_{\mathbf{HCN}}\mathbf{-}{\mathbf{m}}_{\mathbf{H}}\mathbf{-}{\mathbf{m}}_{\mathbf{N}}\\ & \mathbf{=}& \mathbf{7}\mathbf{.}\mathbf{74}\mathbf{}\mathbf{g}\mathbf{-}\mathbf{0}\mathbf{.}\mathbf{287}\mathbf{}\mathbf{g}\mathbf{-}\mathbf{4}\mathbf{.}\mathbf{01}\mathbf{}\mathbf{g}\end{array}$

A 7.74 g sample of HCN is found to contain 0.287 g of H and 4.01 g of N.

Find the mass of carbon in a sample of HCN with a mass of 3.43 g.

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