When ammonia burns in air, nitrogen dioxide and water are produced according to the reaction below:
4 NH₃(g) + 7 O₂(g) → 4 NO₂(g) + 6 H₂O(l)
At 0 °C and 1 atm pressure, burning 44.8 L of ammonia requires:

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Quizplus · Accepted Answer

11ecba4c_d863_c226_99fe_27472ca731fe_MD0008_00 Under conditions of standard temperature and pressure (STP), which is defined as 0 °C and 1 atm of pressure, a gas occupies a volume of 22.4 L for every 1 mole of gas molecules. The moles of a gas present in a given volume at STP can be determined by using this relationship. In a reaction, the moles of gas can be related to the moles of other chemical species by applying stoichiometric mole ratios obtained from the coefficients of a balanced reaction equation. Because the ammonia in the given reaction was burned at 0 °C and 1 atm (STP), the number of moles of NH₃ present in 44.8 L of gas is given by: 11ecba4d_9da8_8d47_99fe_010ba0ac3010_MD0008_11 According to the balanced equation, 7 moles of O₂ are required for every 4 moles of NH₃ that are burned. Using this molar ratio, the required number of moles of O₂ can be found: 11ecba4e_872d_bda9_99fe_f9354fd1e23e_MD0008_11 (Choice A) This is the stoichiometric ratio of the moles of H₂O to the moles of O₂. The molar ratio between H₂O and O₂ cannot be used for the molar proportions between NH₃ and O₂. (Choice B) This value is obtained if the stoichiometric ratio of the moles of NH₃ burned to the moles of O₂ consumed is mistakenly inverted during the second step of the calculation. (Choice C) This is the correct stoichiometric ratio between the moles of NH₃ and the moles of O₂, but this ratio alone does not account for the actual number of moles of ammonia burned during the reaction. Educational objective: Under conditions of standard temperature and pressure (STP), which is defined as 0 °C and 1 atm of pressure, 1 mole of gas occupies a volume of 22.4 L. Mole ratios from balanced chemical reactions can be used to relate the moles of a given gas to the moles of other reaction species.

When Ammonia Burns in Air, Nitrogen Dioxide and Water Are