We can consider a chemical to be safe if it does not contain any harmful substances such as nitrogen, harmful acids, or even excessive heat. Other chemicals such as the chemicals used in food products like, for example, citric acid, is not so harmful.
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Answer:
Explanation:
Reactions occur when two or more molecules interact and the molecules change. Bonds between atoms are broken and created to form new molecules
Atoms are generally neutral because they have an equal amount of protons and electrons.
<u>a) Answer: </u>
<em>Number of molecules in 1 mole</em>
<u>Explanation:</u>
a) Whether we take any of the substance among all three of the given substances they will have the same number of molecules in 1 mole of the substance is considered and the value for this will be 
<u>b) Answer: </u>
<em>In the given question </em><em>mass of the substance</em><em> which is </em><em>greatest</em><em> is asked for </em><em>one mole</em><em> and we also know that </em><em>mass of one mole is given by molar mass. </em>
<u>Explanation:</u>
b) It is known that 
is the molar mass for oxygen which is greater than that of hydrogen while fluorine has a molar mass of 
which on comparison shows that, it is the highest amongst all three.
Chemical change because it cannot be reversed
