AP Chemistry Exam Review

atomic number CORRECT ANSWER The same as the number of protons in the nucleus of an element; it is also the same as the number of electrons surrounding the nucleus of an element when it is neutrally charged. mass number CORRECT ANSWER The sum of an atom's neutrons and protons isotopes CORRECT ANSWER Atoms of an element with different numbers of neutrons Avogadro's number CORRECT ANSWER 6.022×10²³ particles per one mole Moles CORRECT ANSWER grams/molar mass Standard Temperature and Pressure (STP) CORRECT ANSWER Pressure = 1 atm Temperature = 273 K Converting from moles to liters CORRECT ANSWER I mole of gas = 22.4 L Moles and Solutions CORRECT ANSWER Moles = (molarity)(liters of solution) percent composition (mass percents) CORRECT ANSWER The percent by mass of each element that makes up a compound. It is calculated by dividing the mass of each element or component in a compound by the total molar mass for the substance.