Chemistry (II)
What is a chemical reaction?
A chemical reaction occurs whenever bonds between atoms and molecules are created or destroyed.
Define acidic oxides
Acidic oxides are the oxides of non-metals and form acids with water Acidic Oxide + Base → Salt + Water (SO2+2NaOH→Na2SO3+H2O)
Classification of Acids
Acids are often classified on the basis of concentration, strength, source, the presence of oxygen, etc. Acids are found in the laboratory and at home.
What is the difference between base and alkali?
Alkali- dissolves in water Base- neutralizes with acids All alkali are a base but not all bases are alkali
define amphoteric oxides
Amphoteric oxides will react with both acids and bases to form a salt and water Amphoteric Oxide + Acid → Salt + Water Amphoteric Oxide + Alkali → Salt + Water
What are acids?
An acid is a chemical species that donates protons or hydrogen ions and/or accepts electrons. Most acids contain hydrogen.
radioactive isotope
An isotope whose nucleus decays spontaneously, giving off particles and energy.
Isotopes
Atoms with the same number of protons but different numbers of neutrons
define basic oxides
Basic oxides are the oxides of metals. If soluble in water, they react with water to produce hydroxides. Alkali is a water-soluble base. Basic Oxide + Water → Alkali (CaO+H2O→Ca(OH)2) Basic Oxide +Acid → Salt + Water (MgO+2HCl→MgCl2+H2O)
what are some examples of oxides?
CO 2 , SO 2 , CaO, CO, ZnO, Fe 2 O 3, etc.
Work out chemical formulae of the following bases: cesium(l)hydroxide Strontium(ll) hydroxide
CeOH, Sr(OH)2
oxidation reactions
Chemical reactions involving oxygen Corrosion and combustion are two examples of oxidation reactions.
corrosion and combustion
Corrosion and combustion are two examples of oxidation reactions. Metals can undergo both corrosion and combustion reactions, depending on the type of metal and the reaction conditions.
activation energy
Energy needed to get a reaction started
Exothermic and endothermic reactions
Exothermic- heat is produced and exits (more common)(energy down). Endothermic- heat is absorbed (less common)(energy up)
How do indicators change their color in alkali solution?
In an alkali solution alkali turns red litmus paper blue.
What is a salt?
In chemistry, salts are ionic compounds, which when dissolved in water, break up completely into ions. They arise by the reaction of acids with bases(alkalis). Another product of this reaction is always water. Salts always contain either a metal cation (positively charged ion) or a cation derived from ammonium (NH 4 + ) and an acid anion. In solid form, salts have a neutral charge.
What are metals?
Metals can react with a variety of substances, including acids, salts, water, and oxygen. Metals react by losing electrons to form positive metal ions; they then combine with negative ions to form ionic compounds.
define neutral oxides
Neutral oxides don't react with either acids or bases Neutral oxides are neither acidic nor basic they don't show acidic or basic properties. E.g. CO and NO
What are oxides?
Oxides are chemical compounds with one or more oxygen atoms combined with another element. They are binary compounds of oxygen with another element
Classification based on the Strength of the acid
Strong Acids: An acid that can be dissociated completely or almost completely in water is known as a strong acid. For e.g. sulfuric acid, nitric acid, hydrochloric acid, etc. Weak Acids: An acid that doesn't dissociate completely or dissociate negligibly in water is known as a weak acid. For example, those that we usually consume on daily basis - citric acid, acetic acid, etc.
what is a base?
The base is a substance that has to react with water in order to create OH ions.
combustion reaction
a chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light
Law of Conservation of Mass
all the atoms present at the start of the reaction are still present at the end.
reactivity series of metals
an order of reactivity, giving the most reactive metal first, based on results from a range of experiments involving metals reacting with oxygen, water, dilute hydrochloric acid and metal salt solutions
pH scale
measurement system used to indicate the concentration of hydrogen ions (H+) in solution; ranges from 0 to 14
whether a metal will react depends...
not only on the other substance but also on the type of metal. Only some metals react with water. Most metals react with acids. Almost all metals react with oxygen
decomposition reaction
reactions occur when a molecule decomposes, or breaks apart, into two or more molecules. AB= A+B
displacement reaction
reactions occur when one atom kicks another atom out of a molecule. AB+C=CB+A
exchange reaction
reactions occur when one atom trades places with another atom. AB+CD=BD
combination reaction
reactions occur when two or more molecules combine with each other to make a new molecule. A+B=AB
neutral atom
same number of protons and electrons
reactants and products
the substances that enter chemical reactions are called reactants, the substances that result are products.
Corrosion reactions
wearing away due to chemical reactions, mainly oxidation Corrosion reactions are generally very slow
A chemical change can usually be identified because ...
• They are usually very hard to reverse. • There is a large energy change (energy given out or taken in). • There might be a color change. • There might be evidence of a new chemical being made (e.g. bubbles).
