# What mass of oxygen is required to completely consume 9.20 g of ethanol?

Lupe Tanner, Ph.D. | Certified Educator

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To solve this question, we first need to write the balanced chemical equation for the reaction between oxygen (O2) and ethanol (C2H5OH).

The same can be written as:

C2H5OH + 3 O2 -> 2 CO2 + 3 H2O

As per the balanced chemical reaction, 1 mole of ethanol (C2H5OH) reacts with 3 moles of oxygen (O2) to produce 2 moles of carbon dioxide (CO2) and 3 moles of water (H2O).

Here, we have 9.2 g of ethanol. The molecular mass of ethanol is 46 g/mole.

Hence, the number of moles of ethanol in the given mass is 9.2/46 = 0.2 moles.

Since 1 mole of ethanol needs 3 moles of oxygen for complete reaction, 0.2 moles of ethanol will need 0.6 moles (= 0.2 x 3) of oxygen for complete reaction.

The molecular mass of oxygen is 32 g/mole.

Hence, 0.6 moles of oxygen is equal to 19.2 g (= 0.6 moles x 32 g/mole).

Thus, 19.2 g of oxygen is needed for complete reaction with 9.2 g ethanol.

You may solve any question related to chemical reactions and the amount of reactants needed or products generated similarly. To reiterate, write the balanced chemical reaction for the interaction between given species. Use stoichiometry to determine the molar ratios in which species react or get produced. Then convert the given mass of the species into moles and determine how many moles of the other species will be needed/generated. Then multiply the moles of the species reacted/generated by their molar mass to determine the mass needed or generated.

Hope this helps.

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