## Latest Posts

### Reversible Reaction

A reversible reaction ($\rightleftharpoons$) is a reaction that can take place in both directions – i.e. forward reaction and backward reaction. When the rate of forward reaction is equal to the rate of backward reaction, the reaction is said to have reached a state of dynamic equilibrium. When a chemical reaction reaches a state of dynamic equilibrium: the rate of…

### Preparation of Soluble Salts & Insoluble Salts

Preparation of Soluble Salts The methods of preparing soluble salts are categorised into: Solution + Solid Solution + Solution Solution + Solid In the “solution + solid” method, a solid and solution are reacted together to form soluble salt. You may follow the following procedures to prepare soluble salts: Add solid, a little at a time into warm solution. Stir….

### Salts

A salt is an ionic compound formed when the hydrogen atom in an acid is replaced by a metal ion or ammonium ion. Note: Please do not restrict your thinking/interpretation of “salt” to the normal “table salt” in your kitchen. Neutralization is one common reaction whereby a salt is produced. An acid reacts with a base (neutralization reaction) to produce…

### Oxides

Elements react with oxygen (aka. burn in oxygen) in the atmosphere to form oxides. Oxides are classified as: Acidic Basic Amphoteric Neutral   Acidic Oxides Acidic oxides react with water to form acids. Recall: Solutions of these acids in water have a pH value of less than 7. Acidic oxides are oxides of non-metals, which is also known as non-metallic…

### pH Scale & Indicators

The pH scale (as shown in the figure above) is used to measure the acidity or alkalinity of an aqueous solution. The pH scale is numbered between 0 to 14. For reference, the equation for pH is given by: $$\text{pH} =-\text{lg} [\text{H}^{+}]$$ pH is given by the negative logarithm of the concentration of hydrogen ions ($[\text{H}^{+}]$). You can see that…

### Physical & Chemical Properties of Alkalis

Physical Properties of Alkalis Alkalis have the following properties: Alkalis have bitter taste and a slippery soapy feel. Alkaline solutions have pH values greater than 7. (More about pH value in the next sub-topic) Alkaline solutions turn red litmus paper blue. Chemical Properties of Alkalis There are four common reactions of alkalis: Neutralisation reaction Reaction with ammonium salt Precipitation of…

### Introduction To Bases

A base is a compound which, when dissolved in water, dissociates to produce hydroxide ions, $\text{OH}^{-}$ Alternative definition: A base is a metal oxide or hydroxide which reacts with an acid to form water and a metal salt only. Several examples of bases are as follows: Sodium hydroxide: $\text{NaOH} \rightarrow \text{Na}^{+} + \text{OH}^{-}$ Potassium hydroxide: $\text{KOH} \rightarrow \text{K}^{+} + \text{OH}^{-}$…