Definitions:

Question 1

Atomic number

Answer 1

Total number of protons in an atom of an element

Question 2

Mass number

Answer 2

Total number if protons and neutrons in an atom of an element

Question 3

Isotope

Answer 3

An atom of an element with the same number if protons but different number of neutrons

Question 4

Relative atomic mass

Answer 4

Average mass of an atom in comparison to 1 12th of an atom of carbon 12

Question 5

Releative molecular mass

Answer 5

Average mass of 1 formula of that compound in comparison to 1 atom of carbon 12

Question 6

Electronegativity

Answer 6

Power of an atoom to attract a pair of electrons inna covalent bond

Question 7

Molecular formula

Answer 7

Actual number of atoms of each element in a compound

Question 8

Empirical formula

Answer 8

Simplest whole number ratio of atoms of each element present in a compound

Question 9

standard state

Answer 9

substance most stable state under standard conditions - h2o is liquid Na is a solid

Question 10

standard enthalpy of a reaction :

Answer 10

enthalpy change that accompanies a reaction in mo0lar quantities shown in a chemical equation under standard conditions with all reactants and products in their standard state .

Question 11

standard enthalpy of formation :

Answer 11

the enthalpy change that takes place when 1 mole of a compound id formed from its elements under standard conditions with all the reactants and products in their standard state

Question 12

enthalpy change :

Answer 12

change in energy under constant pressure

Question 13

standard enthalpy of combustion :

Answer 13

the enthalpy change that takes place when 1 mole of a substance reacts completely with oxygen under standard conditions , with all reactants and products in their standard state .