The second one is endothermic as endothermic reactions require energy for the reaction to take place.
The number above the symbol is the atomic mass (or atomic weight). This is the total number of protons and neutrons in an atom. The number below the symbol is the atomic number and this reflects the number of protons in the nucleus of each element's atom. Every element has a unique atomic number.
Answer:
The correct answer is - C) a different number of neutrons per atom.
Explanation:
Isotopes of an element are the same element and same atomic number but with different atomic mass and physical properties. The difference in their atomic mass occurs due to isotopes of an element have a different number of neutrons per atom.
The number of protons and the numbers of electrons are the same in the isotopes but only change occurs in the numbers of the neutrons. In isotopes of uranium U-233, U-235, and U-238 have the same number of protons but a different number of neutrons per atom.
Answer:
of acetic anhydride is needed
Explanation:
According to balanced equation, 1 mol of salicylic acid completely reacts with 1 mol of acetic anhydride
Number of moles = (mass)/(molar mass)
Molar mass of acetic anhydride = 102.09 g/mol
Molar mass of salicylic acid = 138.121 g/mol
So, 
of salicylic acid = 
of salicylic acid
Hence, of salicylic acid reacts completely with of acetic anhydride.
So, mass of acetic anhydride needed = 
=
