Atomic mass+Mole+Stochiometry

Question 1

What is atomic mass unit

Answer 1

Atomic mass unit(u) is defined as 1/12 the mass of an atom of ¹²C(Carbon-12, ¹²C isotope(6 protons and 6 neutrons))

Question 2

What is another name for these units

Answer 2

daltons(Da), 1Da=1u

Question 3

What is avarage atomic mass

Answer 3

Avarage relative mass of all the isotopes of a specific element

Question 4

What is molecular mass and what is alternative for ionic compounds

Answer 4

Molecular mass is the mass of the given compound measured in Da or u. It is calculatesld as the sum pf the atomic mass of the atoms that constitute the molecule
For ionic compounds we talk about formula weight

Question 5

What is a mole

Answer 5

1mol is the amount of substance that contains the same elementary units as that contaoned in 12g of carbon-12

Question 6

What is Avogadro number

Answer 6

NA= number of elementary units(atoms) contained in 12g of carbon-12. NA=6.022×10²³

Question 7

What is relatiomship between mol and NA

Answer 7

A mole of some substance is the amount of substance that contains 6.022×10²³ formula units(atoms,molecules,groups of ions etc)

Question 8

What is molar mass

Answer 8

Molar mass(MM) is mass in g/mol and it is the same as molecular mass

Question 9

What is the unit of NA

Answer 9

Atom/mol

Question 10

What are the most important formulas for n

Answer 10

n=m/MM
n=N/NA

Question 11

What is percentage composition

Answer 11

Ratio of the amount of each element present in the compound to the total amount of individual elements present in the compound multiplied by 100
-in compound AnBm
% of A= n×MM(A)×100/MM(comppund)

Question 12

What sign is used whem the substancenis heated

Answer 12

A triangle /_\

Question 13

What is a catalyst

Answer 13

Substance that increases the reaction rate without changing the compound itself

Question 14

In what ways can chemical reactioms be classified

Answer 14

1.Acid-base reactions=involve transfer of proton(H+) from acid to base
2.Redox reactions=involve transfer of e- in simultaneous oxidation and reduction reactions
3.Precipitation reactions=formation of the solid whem 2 solutions are mixed
4.Complexation reactions=formation of complex ion(or and uncharged complex) in which a central metal ion is surrounded by electron-donating ligands

Question 15

How to balance redox reactions

Answer 15

1. Identify what is oxidized and what is reduced and write half equations
2. Balance all elements except O and H
3. a) Balance O by adding H2O
   b) In acidic solution balance H by adding H+. In alkaline solution balance them by adding H2O on the side that needs H+(1H2O per H+) while adding OH- on the other side. Cancel out surplus water
4. Add e-(on the peft for reduction, on the right for the oxidation)
5. Multiply them(if necessary) till the same number of e-
6. Add the equations
7. Simplify it
8. Check

Question 16

What is stochiometry

Answer 16

Relationship between quantities of the reactants and products. It is based on the chem equation and rp between mass and moles

Question 17

What is limiting reactant

Answer 17

Reactant that will be completly used up. While part of the other reactants are in excess