Acids and bases Flashcards
The PH scale
How acidic or alkaline a substance is (the pH of the substance) can be measured using the pH scale, a continuous range that stretches from below 0 to above 14. Most common pH values occur between 0 and 14
What does each ph scale number mean
0-7 = Acids
7 = neutral
7-14 = Alkaline
What is the PH a measure of?
The pH is a measure of the concentration of hydrogen ions in a solution
How can an acid solution be formed?
An acidic solution can be formed when a non-metal oxide is dissolved in water
How can an alkaline solution be formed?
Alkalis are soluble bases. An alkaline solution can be formed when a metal oxide is dissolved in water
Hydrogen and hydroxide ions solubility
Alkalis are soluble bases. An alkaline solution can be formed when a metal oxide is dissolved in water
What happens when an acid is diluted
When an acid is diluted the concentration of H+ ions is decreased and the pH increases towards 7.
What happens when an acid or alkaline is more concentrated
The more concentrated an acid or alkali the better it conducts. When an alkali is diluted the concentration of OH- ions is decreased and the pH decreases towards 7.
What can water molecules do?
Water molecules can break down into hydrogen ions and hydroxide ions.
This is a reversible reaction. A small proportion of water molecules break up to form hydrogen ions and hydroxide ions. Some of these hydrogen and hydroxide ions then react together again to form water molecules.
This is called an equilibrium and is present in water and all aqueous solutions.
What is the concentration of hydrogen ions compared to hydroxide ions in a neutral solution
In water and neutral solutions, the concentration of hydrogen ions is equal to the concentration of hydroxide ions.
What is the concentration of hydrogen ions compared to hydroxide ions in an acidic solution?
All acidic solutions contain more hydrogen ions than hydroxide ions.
What is the concentration of hydrogen ions compared to hydroxide ions in an alkaline solution?
All alkaline solutions contain more hydroxide ions than hydrogen ions.
What happens when you add water to an acidic base?
Adding water to an acid or base will change its pH. Water is mostly water molecules so adding water to an acid or base reduces the concentration of ions in the solution.
When an acidic solution is diluted with water the concentration of H+ ions decreases and the pH of the solution increases towards
What happens when you add water to an alkaline solution?
Similarly, when an alkali is diluted with water the concentration of OH- ions decreases. This causes the pH of the alkali to fall towards 7, making the solution less alkaline as more water is added.
Neutralisation
Neutralisation is the reaction of an acid with a base that results in the pH moving towards 7.
It is a useful process that occurs in everyday life such as in the treatment of acid indigestion and the treating of acidic soil by adding lime.
Neutralisation also moves the pH of an alkali down towards seven.
Several different bases can neutralise acids, and water is always produced as a result of these reactions.
What are the 2 bases?
Metal oxides and alkalis are two types of base. Basic substances neutralise acids, resulting in the pH of the acid increasing towards 7, and water being produced. A soluble base dissolves in water to form an alkaline solution.
Naming salts
To name the salt, the metal ion from the alkali (or base) replaces the hydrogen ion from the acid - (alkali to front, acid to back)
During neutralisation the H+ ion from the acid joins with the OH- ion from the alkali. This is why water is formed in these reactions.
This is true in all neutralisation reactions
How are acids neutralised by metal carbonates?
In the neutralisation reaction between an acid and a metal carbonate, there are three products. The hydrogen ions (H+) from the acid react with the carbonate ions (CO32-) to form water and carbon dioxide gas. A salt is also produced
