Answer: the following are essential factors to be considered when choosing a solvent for crystallization
1. The crystallization solvent should not dissolve the substance to be purified at room temperature, but it should dissolve it well at the solvent’s boiling point
2. The solvent should dissolve soluble impurities well at room temperature.
3. The solvent should not dissolve insoluble impurities even at the solvent’s boiling
point.
4. The solvent must not react with the substance to be purified .
I think that's right like this
Answer:
50distance and 10minutes time
Explanation:
because it's the best object
Answer: 
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
The balanced chemical equation for reaction of potassium superoxide with carbon dioxide to produce oxygen and potassium carbonate will be:

Atomic number is same as the number of protons in the element which is further equal to the number of electrons. As the number of electrons increases in the element, the atomic number of the element also increases.
In periodic table, elements are arranged in the groups, and these groups are columns starting from 1 to 18, elements are arranged in increasing order of atomic number. Elements are placed with difference of one atomic number.
First four elements present in the periodic table is:
atomic number is one (1).
atomic number is two (2).
atomic number is three (3).
atomic number is four (4).
Thus, the series of atomic numbers that represents the ordering of consecutive elements within the periodic table is the last option - 1, 2, 3, 4...