Answer: There are various indicators like litmus paper, phenolphthalein, universal indicator etc. that changes its colour to show the difference between acid and alkali.
Answer: I disagree. Elements form all pure substances, but some pure substances include elements bonded together to form molecules and compounds.
Explanation:
Pure substances are those that have a uniform and constant (invariable) composition.
That condition is met by both elements and compounds.
Elements are pure substances of one only kind of atoms. For example, gold, oxygen, sodium, hydrogen, are pure substances that arer elements. There are 118 elements known and they are all listed in the periodic table.
Compounds are pure substances formed by two or more different kind of atoms. Water (H₂O), table salt (NaCl), and ethanol (CH₃-CH₂OH), are examples of pure substances that are compounds. There are pratically infinite different compounds.
In conclusion, compounds are also pure substances, since every sample of a given compound has always the same kind of elements bonded in the same way.
AlPO4----> Al+3 + PO4-3
Ksp= [Al+3] x [PO4-3]= 9.84 x 10^-21
Ksp= (x) (x)= x^2
X^2= 9.84x10-21
x= 9.92 x 10^-11
The molar solubility is 9.92 x 10^-11
I would say it should be Einstein's famous equation of e=mc^2 which means energy =mass x the speed of light squared. With this equation Einstein showed that energy comes from a mass travelling at the speed of light squared which is a fundamental equation to explain physical phenomena.
