Video Transcript
Which of the following is not a property of nitrogen gas? (A) Its structure is two nitrogen atoms joined by a triple covalent bond. (B) It is a colorless, odorless, tasteless gas. (C) It has a neutral effect on litmus paper. (D) It is heavier than air. Or (E) it is slightly soluble in water.
Atomic nitrogen can be found in group 15 of the periodic table. A neutral atom of nitrogen has seven electrons, five of which are in its outer shell. To satisfy the octet rule, which states that atoms create chemical bonds to have eight valence shell electrons and the same electron configuration as the nearest noble gas, nitrogen forms a strong triple bond. We call this diatomic nitrogen, dinitrogen, or nitrogen gas. As nitrogen is a nonmetal, and the electrons in the triple bond are shared, we can class the bond as a triple covalent bond.
The question asks us which of the following is not a property of nitrogen gas. We have just determined that option (A), its structure is two nitrogen atoms joined by a triple covalent bond, is a property of nitrogen gas. Thus, option (A) cannot be the answer to this question. Option (B) is “It is a colorless, odorless, tasteless gas.” Nitrogen is used in food packaging to provide an inert atmosphere and stop the oxidation of food before it’s eaten. It is chosen for this as it is colorless, odorless, and tasteless. So, option (B) is also a property of nitrogen gas. Thus, it is not the answer to this question.
Option (C) is “It has a neutral effect on litmus paper.” Nitrogen is an inert gas with no acidic or basic properties, so having a neutral effect on litmus paper is a property of nitrogen gas. Thus, option (C) is not the answer to this question either. Option (D) is “It is heavier than air.” Air is composed of approximately 78 percent nitrogen, 21 percent oxygen, and one percent of a mixture of other gases, including water vapor. As there are only around one percent of other gases, the mass of these gases doesn’t affect the overall mass very much. So, we can ignore these for the purpose of answering this question.
Apart from nitrogen, the other main component of air is oxygen. If we find oxygen on the periodic table, we can see that its mass number is larger than the mass number of nitrogen. So, the combination of nitrogen with a heavier gas, oxygen, will be heavier than nitrogen by itself.
Option (D) suggests that nitrogen is heavier than air. This is not a property of nitrogen gas, as nitrogen gas is lighter than air. So, it seems like option (D), it is heavier than air, may be the answer to this question. But to confirm, let’s look at option (E): it is slightly soluble in water. This is true. At 20 degrees Celsius, only 0.002 grams of nitrogen dissolves in 100 grams of water. So, as this is a property of nitrogen gas, Option (E) cannot be the answer to this question.
So, the answer to the question “Which of the following is not a property of nitrogen gas?” is (D), it is heavier than air.
