How many molecules of carbon disulfide will react with 4.21 x 1019 molecules of oxygen?

             1.4 × 10¹⁹ molecules of CS₂

Explanation:

The chemical equation is as follow,

                            CS₂  +  3 O₂    →    CO₂  +  2 SO₂

According to this equation,

1.8 × 10²⁴ molecules (3 mole) of O₂ reacts with  =  6.022 × 10²³ molecules (1 mole) of CS₂

So,
         4.21 × 10¹⁹ molecules of O₂ will react with  =  X molecules of CS₂

Solving for X,
                      X  =  (4.21 × 10¹⁹ × 6.022 × 10²³) ÷ 1.8 × 10²⁴

                      X  =  1.4 × 10¹⁹ molecules of CS₂

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