Important formulae :

1. \(No\ of\ moles =\frac{mass}{Molar\ mass}\)
2. \(No\ of\ moles\ of\  gas=\frac{Volume\ at\ STP}{22.4}\)
3. \(No\ of\ moles\ of\  Particles=\frac{No\ of\  Particles}{6.023\times 10^{23}}\)
4. \(No\ of\ moles\ of\ solute=Molarity \times  Vol(L)\)
5. \(Eq.\ wt.\ of\ a\ salt=\frac{M.W.\ of\ salt}{Total\ +ve\ \ charge\ of\ metal\ ion}\)
6. \(Eq.\ wt.\ of\ element=\frac{Atomic\ Weight}{Valency}\)
7. \(Avg.\ atomic\ mass=\frac{m\times a+n\times b}{m+n}\) where, a + b are atomic masses and m + n are precentage.
8. \(\%\ of\ element\ in\ compound =\frac{n(at\ mass\ of\ element)}{MW\ of\ compound}\times 100\) where, n= No. of atoms of that element
9. \(Molarity=\frac{w\times 1000}{M.W.\times V(ml)}\)
10. \(Normality=\frac{w\times 1000}{E.W.\times V(ml)}\)
11. \(Molality=\frac{w\times 1000}{M.W.\times W(g)}\) W = Weight of solvent
12. \(Mole\ fraction(X)=\frac{n}{n+N}\)
13. \(\%W/W=\frac{W\times 100}{W+W_{0}}\)
14. \(ppm=\frac{weight(vol)\ of\ solute\times 10^{6}}{weight(vol)\ of\ solution}\)
15. \(Molecalar\ weight =2\times V.D.\)
16. \(Eq.\ wt.\ of\  metal=\frac{Wt.\ of\ metal}{wt.\ of\ H_{2}\ displaced}\times 1.008\)
17. \(Eq.\ wt.\ of\  metal=\frac{Wt.\ of\ metal\times 11200}{Vol\ of\ H_{2}\ displaced\ at\ STP  (mL)}\)
18. \(Eq.\ wt.\ of\  metal=\frac{Wt.\ of\ metal\times 35.5}{Wt.\ of\ Chlorine\ combined}\)
19. \(Eq.\ wt.\ of\  metal=\frac{Wt.\ of\ metal\times 11200}{Vol\ of\ Cl_{2}\ combined\ at\ STP (mL)}\)
20. \(Eq.\ wt.\ of\  metal=\frac{Wt.\ of\ metal\times 8}{Wt.\ of\ oxygen\ combined}\)
21. \(Eq.\ wt.\ of\  metal=\frac{Wt.\ of\ metal\times 5600}{Vol\ of\ O_{2}\ displaced\ at\ STP (mL)}\)
22. \(Molority=\frac{\%W/W\times density\times 10}{Molecular\ weight}\)
23. \(M_{1}V_{1}=M_{2}V_{2}\ (Molarity\ equation)\)
24. \(N_{1}V_{1}=N_{2}V_{2}\ (Normality\ equation)\)
25. \(n=\frac{Molecular\ weight}{Empirical\ formula\ Weight}\)
26. \(^{\circ}F=\frac{9}{2}(^{\circ}C)+32\)
27. \(K=^{\circ}C+273.15\)
28. \(1L=1dm^{3},\ 1mL=1cm^{3}\)

Important Facts :

1. Antoine Lavoisier - Law of conservation of mass
2. Joseph proust - Law of definite proportions
3. John Dalton - Law of Multiple proportions
4. Richter - Law of combining weights.
5. Gay Lussac - Law of combining Volumes.
6. \(1\ amu=1.6605\times 10^{-23}\ gram\)
7. \(Mass\ of\ C\ atom=1.9926\times 10^{-23}\ gram\)
8. \(Avogadro's\ number(N_{A})=6.022\times 10^{23}\)
9. AZT = Azido thymidine,drug used for aids victims.
10. The limiting reagent is the reagent that is entirely consumed when a reaction goes to completion. Its amount limits the amount of the product formed.

Precision and Accuracy.

The term precision refers for the closeness of the set of values obtained form identical measurements of a quantity.

Accuracy refers to the closeness of a single measurement to its true value.

Let us take an example to illustrute. this. Three students were asked to determine the mass of a piece of metal where mass is known to be 0.520g. Data obtained by each Student are recorded in table below

The data for student A are neither, precise nor accurate. The data for student B are precise but not accurate. The data for student C are both precise and accurate.