Question

What is an acid? Write four properties of acids by giving examples.

Answer 1

Hint: The \[pH\] scale ranges from \[0{\text{ }}to{\text{ }}14\] , and most solutions fall within this range. Any solution lying below \[7.0\] is considered to be acidic while above \[7.0\] is alkaline. If the solution has a pH of \[7.0\] then it is considered to be neutral.

Complete step by step answer:
An acid can be defined as a chemical which releases hydrogen ions in water thereby forming salts by integrating with specific metals. \[pH\] scale can be used to measure acidity. On the \[pH\] scale, value of \[7.0\] is considered to be neutral, whereas, a value from \[7.0\] to \[0\] indicates increasing acidity. The properties of acids are listed below:
1) Acids react with the active metals and yield hydrogen gas. An example is shown below:
$Zn(s) + {H_2}S{O_4}(aq) \to ZnS{O_4}(aq) + {H_2}(g)$
2) When an acid reacts with a base, they have the tendency to form a salt. An example is shown below:
$NaOH + HCl \to NaCl + {H_2}O$
3) Acids have the tendency to change the colour of specific acid-base indicators. Most common indicators include litmus paper and phenolphthalein. Example: Blue litmus paper turns into red colour in the presence of an acid, whereas phenolphthalein turns colourless.
4) Acids possess a sour taste. Examples: Lemons containing citric acid, vinegar containing acetic acid
5) Aqueous solutions of acids are considered to be electrolytes, as they conduct an electrical current.

 Note: There are certain factors that influence acidity which are: (i) Electronegativity: Acidity goes on increasing as you move from left to right in a periodic chart. (ii) Anion size: Acidity goes on increasing as you move from top to down in a periodic chart. (iii) Resonance: Anions having resonance structures are more acidic in comparison to anions which don't have.