26-50 ways to pass the regents

26. A solute is the substance being dissolved, while the solvent is the substance that

dissolves the solute. (Water is the solvent in Kool-Aid, while sugar is the solute.)

27. Isotopes are written in a number of ways: C-14 is also Carbon-14, and is also

mass number 14C

atomic number 6

28. The distribution of electrons in an atom is its electron configuration.

29. Electron configurations are written in the bottom center of an element’s box on the

periodic table in your reference tables.

# of electrons in 3rd principal energy level

# of electrons in 2nd principal energy level

# of electrons in 1st principal energy level

30. Use the mole triangle diagram on the next page to help you solve conversions

between moles, grams, numbers of molecules/atoms, and liters of gases at

STP...

31. The electron configurations on Periodic table are ground state configurations, atoms absorb

energy and electrons move to higher energy levels (excited) when the fall back to lower levels

energy is released by the atom, many times in the form of visible light called an emission

spectrum, MAX number of electrons in each level 2(n^2), meaning 2-8-18-32...

32. Polyatomic ions (Table E) are groups of atoms with an overall charge.

NO3

1-, NH4

1+, SO4

2-, etc.

33. Coefficients are written in front of the formulas of reactants and products in

chemical equations. They give us the ratios of reactants and products in a

balanced chemical equation.

34. Chemical formulas are written so that the charges of cations and anions

neutralize one another.

Example: calcium phosphate:

Ca2+ PO4

3- = Ca3(PO4)2

35. When naming binary ionic compounds, write the name of the positive ion (cation)

first, followed by the name of the negative ion (anion) with the name ending in

“-ide.” Example:

KCl MgS

Potassium chloride Magnesium sulfide

36. When naming compounds containing polyatomic ions, keep the name of the

polyatomic ion the same as it is written in Table E.

Example:

NH4Cl NH4NO3

Ammonium chloride Ammonium nitrate

37. Physical changes do not form new substances. They merely change the

appearance of the original material. (The melting of ice)

38. Chemical changes result in the formation of new substances.

(The burning of hydrogen gas to produce water vapor)

39. Reactants are on the left side of the reaction arrow and products are on the right.

40. Endothermic reactions absorb heat. The energy value is on the left side of the

reaction arrow in a forward reaction.

41. Exothermic reactions release energy and the energy is a product in the reaction.

42. Only coefficients can be changed when balancing chemical equations!

43. Synthesis reactions occur when two or more reactants combine to form a single

product. Example: 2H2(g) + O2(g)  2H2O(g)

44. Decomposition reactions occur when a single reactant forms two or more

products. Example: CaCO3(s)  CaO(s) + CO2(g)

The electron configurations on Periodic table are ground state configurations, atoms absorb

energy and electrons move to higher energy levels (excited) when the fall back to lower levels

energy is released by the atom, many times in the form of visible light called an emission

spectrum, MAX number of electrons in each level 2(n^2), meaning 2-8-18-32...

45. Single replacement reactions occur when one element replaces another

element in a compound.

Example: Mg + 2HCl  MgCl2 + H2

46. Double replacement reactions occur when two compounds react to form two

new compounds.

Example: AgNO3 + KCl  AgCl + KNO3

47. The masses of the reactants in a chemical equation is always equal to the masses

of the products. “Law of Conservation of Mass.”

48. The gram formula mass of a substance is the sum of the atomic masses of all of

the atoms in it. H2SO4 = 98 g/mole

2 x H = 2 x 1 g/mole = 2 g/mole

1 x S = 1 x 32 g/mole = 32 g/mole sum = 98 g/mole

4 x O = 4 x 16 g/mole = 64 g/mole

49. Know how to calculate the percentage composition of a compound. (Formula is

on Table T.)

50. Need to know how to do mole to mole stoichiometry. use ratio from balanced equation.