Chemistry Chapter 2: Reactions and Stoichiometry

What is a chemical reaction? Give an example.  

A chemical reaction is the behaviour of matter when it comes into contact with other matter. For example, the tarnishing of sodium metal when it is exposed to air.  

What happens to atoms during a chemical reaction? 

Atoms are rearranged, forming new substances while preserving mass.

What is the “law of conservation of mass”? 

Matter can not be created or destroyed. 

What is a Skeleton Equation?

A skeleton equation is a chemical equation that shows the reactants and products of a reaction without indicating their relative amounts or coefficients. It is a basic representation of the compounds involved in the reaction.

Why is a skeleton equation incomplete?

A skeleton equation is incomplete because it does not provide the coefficients needed to balance the equation, thus lacking information about the relative amounts of reactants and products.

Law of definite proportions

A principle stating that a chemical compound always contains its constituent elements in fixed ratio by mass, regardless of the sample size or source.

Why is classification of reaction important in chemistry?

1. Predicting Products 

2. Understanding Reaction Behaviour

How do we know a reaction has happened?

A new substance is obtained.

Synthesis Reaction

Type of reaction where a more complex substance is produced from simpler reactants. A+B——> AB

Decomposition reaction

Type of reaction where a complex substance is broken down into simpler products. AB———> A+B

Single Displacement Reaction

Type of reaction where one element replaces another in a compound. AB+ C————> AC+ B

Double Displacement Reaction

Type of reaction where two compounds exchange ions or bonds to form two new compounds. AB+CD———> AC+ BD

Limiting Reagent

Reagent that runs out first, causing the reaction to stop.

Excess Reagent

Leftover reagent that has not had a chance to react. Present in greater quantity than necessary for a reaction to complete.