1. Basic Concepts Of Chemistry Flashcards
Significant figures
Significant figures are the digits within a number to determine how accurate the data value is .
Rules to determine Significant values.
- All non zero number are significant.
- Zeros between any two non zero number are significant.
- Zeros after the decimal are significant.
- Zero and coefficient of scientific notations are significant.
- Any leading zeros are not significant.
- Zeros in larger numbers are not significant.
Significant values rules for arithmetic operations.
Addition and Subtraction
Look for least amount of decimal places .
Multiplication and Division
Look for least amount of significant figures.
Precision and Accuracy
Precision
The closeness of measurement for a particular quantity.
Accuracy
The particular value closest to the true value of a quantity.
Dimensional analysis
1. Length
-1in = 2•54cm
-1ft = 12in
-1yd = 3ft
-1m = 1•0936yd
-1mi = 1609•3m
-1mi = 1•609km
Dimensional analysis
2. Mass
-1kg = 2•205lb
-1lb = 453•6g
-1oz = 28•3495g
Dimensional analysis
3.Volume
-1L = 1dm³
-1ml = 1cm³
-1dm = 10cm
-1L = 1•057qt(quart)
-1ft³ = 28•317L
-1gal = 4qt
Dimensional analysis
4. Time
-1hr = 60min
-1min = 60sec
-1hr = 3600sec
Law of Conservation of Mass
Mass can neither be created nor be destroyed.
In all physical and chemical changes there is no net change in mass during the process.
Law of Definite Proportion
Irrespective of the source, a given compound contains same element combined together in same proportion by mass.
A given compound always contains exactly the same proportion of elements by weight ,whether the element source is organic or inorganic the proportion remains same .
Law of Multiple Proportion
When two elements combine to form more than one compound then masses of the element combined with a fixed mass of other element are in the ratio of small whole numbers.
Eg.-
H² +O = H²O
2g 16g 18g
H² + O² = H²O² 2g 32g 34g
Here Oxygen (16g and 32g) combine with fix mass of Hydrogen (2g) bears a ratio ( 16:32 i.e 1:2 )
Gay Lussac’s Law of Gaseous Volume
Also known as Law of Definite Proportion by Volume
When gases combine or are produced in a chemical reaction they do so in a simple ratio by volume provided all gases are in same temperature.
Avogadro’s Law
“Gases are equal volumes at same temperature and pressure contains same amount of molecules.”
Atomic mass
“The atomic mass unit is assigned a value exactly equal to the mass of 1/12th of ¹²C atom . ”
So, 1amu = 1.660×10^-24 g
Amu= atomic mass unit
Average Atomic mass
It is the atomic mass used for calculations . All the isotopes relative abundance and atomic mass are taken in accordance to measure the average mass .
**Average Atomic mass “= (relative abundance of isotope)(atomic mass of isotope)+………….
Molecular mass and Formula mass
Molecular mass is the mass of any compound whole formula mass is of ions making compound.
Mole and molar mass
**One mole = atoms in 12g of ¹²C or Carbon-12 **
One mole of any substance, is always same i.e
Na= 6.022×10^23 atoms/mole
Na is avogadro’s constant.
**The mass of one mole of any substance in grams is called it’s molar mass . **
Percentage Composition
It is used to check the purity of an element in a compound.
Mass percent of an element = (Mass of element in compound÷
Molar mass of the compound)×100
Empirical formula
**Empirical formula represents the ratio of atoms present in the elements in the compound in simple whole numbers **
Steps -
1. Convert mass percent into grams if given if grams given ignore
2. Find number of moles of each element
3. Divide the ratio of moles such that they are in simple whole number
4. Use the ratio to write empirical formula
5. Find the empirical formula mass
6. Divide the given molar mass with EFM
7. Multiply the result with empirical formula
8. This is the molecular formula.
Mass per cent
As the name say mass per 100gm
Mass per cent = (mass of solute ÷ mass of solution)×100
Mole Fraction
Ratio of no. Of moles of an element in compound
Say there are two elements whose nom of moles are Na and Nb then,
Mole fraction of A = _____Na______
(Na+Nb)
Mole fraction of B = _____Nb______
(Na+Nb)
Molarity
The number of moles of solute dissolve in 1L of solution. Used to determine how concentrated the solution is.
Molarity= No. of moles of solute ÷
Volume of solution in L
Volume of solution= solute +solvent
Solute remains constant but water or any other solvent is added to it later and made together up to 1 L i.e the mass of solvent is changing with every other solute .
Molarity is affected by temperature since volume depends upon the temperature.
Molality
The number of moles of solute dissolved in 1kg solvent.
Molality= No. of moles of solute ÷
Mass of solvent in kg
The mass of solute and solvent are fixed and mixed as it is .
Molality doesn’t depend upon the temperature since mass remains constant ( it never change to begin with)
Limiting reactant
The reactant in a reaction who gets used up the fastest and produce the least amount of product is called Limiting reactant.
The other reactant in the reaction is excess reactant and the product produced by limiting reactant is called the theoretical yeild.
