Answer:
Several principal emissions result from coal combustion: Sulfur dioxide (SO2), which contributes to acid rain and respiratory illnesses.
Explanation:
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The average speed is calculated using the following formula
Where

T = 298 K [room temperature]
m = mass of each molecule of oxygen
mass of one mole of oxygen molecules = 32 g / mol
mass of one molecule of oxygen will be = 
mass of one molecule of oxygen will be = 
putting values
average speed = 
Average speed = 482.19 m / s
average speed = 1735.8 km / h
so approx = 1700 km/h
Answer is 3
because on the periodic table, the small number above every element is the number of protons
Answer:
Dmitri Mendeleev
Explanation:
He was a Russian Scientist who decided to reorganize the periodic table after other notable scientists such as Antoine-Laurent Lavoisier had also tried to organize it based on the states of matter of the elements.
Mendeleev reorganized the period in the order of increasing atomic mass although there were some other modifications by modern scientists.