Which is defined as the measure of quantity proportional to the number of atoms

Indicate whether the specified alkyl halides will form primarily substitution products, only elimination products, both substitution and elimination products, or no products when they react with sodium methoxide. 1-bromobutane 1-bromo-2-methylpropane 2-bromobutane 2-bromo-2-methylpropane

Which symbol can be used to indicate the pressure at which a chemical reaction is carried out? 25°c 2 atm pa

How many atoms or molecules are there in a mole of a substance?