Chemical Equations/Oxidation Numbers

Chemical equations represent the reaction between two or more (a)   atoms, molecules, or compounds. The (b)   represent the starting materials in the reaction and are listed on the left side of the equation. The (c)   represent the substances that form during the reaction and are listed on the right side of the equation. The arrow reads as " (d)   ," so reactants yield products.

• elemental
• reactants
• products
• yields

Tags

NGSS.MS-PS1-1

Reactants react to make a product.

• Reactants react to make a product.
• Reactants do not interact.
• Products react to make reactants.
• Reactants are products.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Chemical equations also include the physical state of each substance. Each state has an associated abbreviation and is listed in italics after the chemical formula:

• 
  

• • solid (s)

• • liquid (l) 

• • gaseous (g)

• • aqueous (aq): substances dissolved in water 

For example, in the following reaction, both reactants are aqueous, and combine to form a solid precipitate, barium chloride, and an aqueous solution of sodium nitrate: 

2NaCl(aq)+ Ba(NOX3​)X2​(aq) → BaClX2​(s) + 2NaNOX3​(aq)

• fale

• True

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

​ (a)   illustrate the law of ​ (b)   , so both the reactant and the product sides of the ​ (c)   have the same number of each atom. ​ (d)   utilize coefficients to represent a balanced number of each of the molecules or compounds. Coefficients are placed directly in front of the substance that they modify.

• reaction
• Chemical equations
• conservation of matter
• Reactions

Tags

NGSS.MS-PS1-5

Subscript vs Coefficient

• Coefficient shows the number of atoms; subscript shows the type of atoms in a molecule.
• Coefficient indicates the type of molecule; subscript indicates the total number of molecules.
• Coefficient is used for balancing equations; subscript is irrelevant in chemical formulas.
• Coefficient indicates quantity of molecules; subscript indicates number of atoms in a molecule.

Tags

NGSS.HS-PS1-7

In a chemical equation, a (a)   is a number written in front of a chemical formula that indicates how many molecules of that substance are involved in the reaction, while a (b)   is a small number written below an element symbol within a chemical formula that shows how many (c)   of that element are present in a (d)  

• coefficient
• subscript
• atoms
• molecule

you can change ​ (a)   to balance an equation, but you cannot change ​ (b)   as it would alter the identity of the substance itself

• coefficients
• subscripts

Tags

NGSS.HS-PS1-7

An ______ is used to keep track of how many electrons an atom has at the moment.

• mass number
• oxidation number

• neutron count
• electron affinity

To determine if electrons are lost or gained, the oxidation number must first be identified following these rules:

• All free elements, such as H₂, S₈, and Mg, have an oxidation number of 0

• Monatomic ions have an oxidation number equal to their charge

  • For example, K⁺ has a charge of +1

• True

• False