# 4 g of carbon was heated with 8 grams of Sulphur. How much CS2 was formed when the reaction is completed.

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4 g of carbon was heated with 8 grams of Sulphur. How much CS2 was formed when the reaction is completed. Find out the amount of reactant left unreacted.

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$4C + S_8 \rightarrow 4CS_2$

$\therefore$ Number of moles of carbon = $\frac 4{12} = 0.33 \,mol$

Number of moles of sulphur = $\frac 8{256.8} = 0.031\, mol$

$\because$ 1 mole of S8 react with =  4 mole of carbon

$\therefore$ 0.031 mole of S8 react with = (4 x 0.031) mole of carbon

= 0.12 mol of carbon

but we have 0.33 moles of carbon

$\therefore$ S8 is a limiting reagent.

$\therefore$ Number of moles of CS2 formed = 0.031 x 4

$\therefore$ Weight of CS2 =  0.031 x 4 x 76 = 9.42 g

Number of moles of carbon left = 0.33 - 0.12 = 0.21 mol

or

= 0.21 x 12 g

= 2.52 g

Hence, 9.42 g CS2 will formed and 2.52 g carbon left unreacted.