Answer:
- <em><u>Mendeleev produced the first orderly arrangement of known elements.</u></em>
- <em><u>Mendeleev used patterns to predict undiscovered elements.</u></em>
Explanation:
- <u>Mendeleev produced the first orderly arrangement of known elements and used patterns to predict the undiscovered elements.</u>
Those two statments are true.
For the time being there were some 62 known elements. Before Medeleev some schemes to order part of the elements were proposed, but Medeleev showed the relationship between the atomic mass and the properties of the elements (supports second choice). This arrangement is known as the periodic table.
More importantly, Mendeleev predicted correctly the existance and properties of unknown elements, which is his major contribution: he left blanket spaces which where gradually filled when new elements where discovered (this supports the fourth choice).
The first modern chemistry book was written by Antoine Lavoisier (this discards first option).
Mendeleev ordered the elements by increasing mass number (this discards third choice), which was corrected later by the scientist Henry Moseley, who ordered the elements by increasing atomic number (number of protons).
Isotopes were not known by Mendeleev times, so this discards the last option.
Answer:
Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids and gases from contaminated water. The goal is to produce water fit for a specific purpose. Most water is purified for human consumption (drinking water), but water purification may also be designed for a variety of other purposes, including meeting the requirements of medical, pharmacological, chemical and industrial applications. In general the methods used include physical processes such as filtration,sedimentation, and distillation, biological processes such as slow sand filters or biologically active carbon, chemical processes such asflocculation and chlorination and the use of electromagnetic radiation such as ultraviolet light.
Extreme lack or loss of water may lead to dehydration of the body and other health complications. For this reason, governments ensure that citizens have access to clean and safe water for domestic use. Clean water is essential in ensuring that no pathogens or impurities are ingested by people, either through direct drinking or through food.
To attain these standards of water, purification is important. Water purification involves physical and chemical processes, which are carried out stepwise to ensure the water is safe and free from any harm. This directional process essay synthesizes the steps, which have to be followed to achieve this task.
In essence, water purification denotes the process used to free water from impurities like bacteria and contaminants. Since the process is aimed at eliminating all the impurities present in the water, it is necessary to apply chemical and physical methods of separation in an orderly manner.
Explanation:
Answer:
2.1 x 10^24 Cr ions
Explanation:
You need to multiply the 3.5 mol by the Avogrado's number (6.022 x 10^23) to get your answer.
Answer:
carbon
Explanation:
tbh im not sure just guessing
Answer:
After 2 half-lives there will be 25% of the original isotope, and 75% of the decay product. After 3 half-lives there will be 12.5% of the original isotope, and 87.5% of the decay product. After 4 half-lives there will be 6.25% of the original isotope, and 93.75% of the decay product.
Explanation:
