a) Why oxygen exists in a fixed ratio 21% in the atmosphere? b) The role of the atmosphere on Earth. 相关知识点: 试题来源: 解析 a) 氧气在大气中以固定比例21%存在的原因主要是由于生物地球化学循环的平衡。植物和其他光合作用生物通过光合作用释放氧气,而动物和微生物通过呼吸作用消耗氧气。此外,...
Oxygen is a colourless gas that exists in large quantities in the air. All plants and animals need oxygen in order to live. e.g. The human brain needs to be without oxygen for only four minutes before permanent damage occurs. 人的大脑缺氧4分钟后便会造成永久性损伤。
Symbol O A nonmetallic element that exists in its free form as a colorless, odorless gas and makes up about 21 percent of the Earth's atmosphere. It is the most abundant element in the Earth's crust and occurs in many compounds, including water, carbon dioxide, and iron ore. Oxygen comb...
Energy (light) may also activate oxygen, generating the so-called singlet oxygen forms. All these reactive oxygen forms are called “ROS.” In the lay press these forms are regularly indicated as oxygen radicals. This is not correct because not all of these intermediate oxygen species contain ...
Oxygen (O) is an odorless, colorless, gaseous elementthat belongs to group 16 (formerly group VI) of thePeriodic Table. It is the most abundant elementin the earth's crust (49.2% by weight), is present in theatmosphere (20% by volume) and is a constituent ofwater. It exists in three...
Symbol O A nonmetallic element that exists in its free form as a colorless, odorless gas and makes up about 21 percent of the Earth's atmosphere. It is the most abundant element in the Earth's crust and occurs in many compounds, including water, carbon dioxide, and iron ore. Oxygen comb...
Oxygen is the third most common element in the universe and the most common in the Earth’s crust (49%). However, because oxygen is highly reactive, most of it is bound to other elements to form chemical compounds. Elementary oxygen in its two allotropes O2 and O3 (ozone) o...
The fire that killed the Apollo 1 crew on a test launchpad spread so rapidly because the pure oxygen atmosphere was at normal atmospheric pressure instead of the one third pressure that would be used during an actual launch. Read more on oxygen in water Back to periodic table. see also oxy...
They focused on studying the diffusion kinetics of Zn2+ ions and found that there exists a low energy barrier of the order of 0.24 eV for Zn atom mobility close to the vacancy in comparison to the existence of higher Zn mobility energy barrier in optimal ZnMn2O4, which is of the order ...
Symbol O A nonmetallic element that exists in its free form as a colorless, odorless gas and makes up about 21 percent of the Earth's atmosphere. It is the most abundant element in the Earth's crust and occurs in many compounds, including water, carbon dioxide, and iron ore. Oxygen comb...