Module 2:Foundations In Chemistry

Question 1

Carbon-12

Answer 1

The standard isotope which is used to base all atomic masses .The international standard for the measurement of atomic masses

Question 2

Relative isotopic mass

Answer 2

Relative isotopic mass is the mass of an isotope relative to 1/12 th of an atom of carbon-12

Question 3

Relative atomic mass

Answer 3

Is the weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12

Question 4

Mass to charge ratio formula

Answer 4

Mass to charge ratio M/Z = relative mass of ion / relative charge on ion

Question 5

Binary compound

Answer 5

Contains two elements only

Question 6

Polyatomic ions

Answer 6

An ion may contain more than one element bonded together.

Question 7

Avogadro constant

Answer 7

6.02 x 10^23

Question 8

Mole / Amount

Answer 8

Amount n = mass m/molar mass M

Question 9

Molecular formula

Answer 9

The number of atoms of each element in a molecule e.g. H2,F2

Question 10

Empirical formulae

Answer 10

The empirical formula is the simplest whole number ration of atoms of each event in a compound e.g. C2H6 would become CH3

Question 11

Relative molecular mass

Answer 11

Compares the mass of a molecule with the mass of an atom of carbon-12

Question 12

Relative formula mass

Answer 12

Relative formula mass compares the mass of a formula unit with the mass of an atom of carbon-12

Question 13

Standard solution

Answer 13

A solution of a known concentration

Question 14

Molar gas volume

Answer 14

The volume per mole of gas molecules at a stated temperature and pressure

Question 15

Mole formula

Answer 15

Mole=conc x volume

Question 16

What are the assumptions for the molecules making up an ideal gas

Answer 16

-random motion
-elastic collisions
-negligible size
-no intermolecular forces

Question 17

Ideal gas equation and values

Answer 17

pV=nRT
T:temperature (+273K)
R:ideal gas constant (8.31Jmol^-1K^-1)
n:amount of gas molecules (mol)
V:volume(m^3)
p:pressure(Pa)

Question 18

Conversions for ideal gas equation

Answer 18

Cm^3 to M^3 = x10^-6
dm^3 to m^3 = x 10^-3
Degrees Celsius to K(kelvins)=+273
kPa to Pa = x10^3

Question 19

Stoichiometry

Answer 19

In a balanced equation , the balancing numbers give the ratio of the amount in moles of each substance.This ratio is called stoichiometry of the reaction

Question 20

Percentage yield equation

Answer 20

Percentage yield = )
(actual yield / theoretical yield) x 100

Question 21

Limiting reagent

Answer 21

The reactant that is not in excess will be completely used up first and stop the reaction

Question 22

Atom economy

Answer 22

Atom economy=(sum of molar masses of desired products/ sum of molar masses of all products) x 100

Question 23

Strong acid

Answer 23

A strong acid like HCl releases all its hydrogen atoms into a solution as H+ ions and completely dissociated in aqueous solution

Question 24

Weak acid

Answer 24

A weak acid such as ethanoic acid , CH3COOH , only releases a small proportion of its available hydrogen atoms into solutions as H+ ions .A weak acid partially dissociates in aqueous solution

Question 25

Bases

Answer 25

A base neutralises an acid to form a salt

Question 26

Alkali

Answer 26

An alkali is a base that dissolves in water releasing hydroxide ions (OH-) into the solution

Question 27

Name the Salts of the following acids : hydrochloride acid , sulfuric acid , ethanoic acid, nitric acid

Answer 27

HCl: chloride H2SO4:sulfate HNO^3:nitrate CH3COOH:ethanoate

Question 28

What is titration

Answer 28

A technique used to accurately measure the volume of one solution that reacts exactly with another solution.It can be used to: -Finding the concentration of a solution -identification of unknown chemicals -finding the purity of a substance

Question 29

Oxidation number

Answer 29

It is based on a set of rules that apply to atoms and can be thought of as the number of electrons involved in bonding to a different element .

Question 30

Rules for elements oxidation number

Answer 30

The oxidation number is always zero for elements -in a pure element any bonding to atoms of the same element -So in H2, O2, P4 and Fe the oxidation number of each of the elements is 0

Question 31

Rules for compounds and ions oxidation number

Answer 31

-Each atom in a compound has an oxidation number -An oxidation number has a sign , which is placed before the number

Question 32

Oxidation number for O

Answer 32

-2

Question 33

Oxidation number for H

Answer 33

+1

Question 34

Oxidation number for F

Answer 34

-1

Question 35

Oxidation numbers in special cases

Answer 35

H in metal hydrides : -1 O in peroxides: -1 O bonded to F : +2

Question 36

Oxidation and reduction definition in terms of reactions involving oxygen

Answer 36

Oxidation: addition of oxygen Reduction: removal of oxygen

Question 37

Redox in terms of electrons

Answer 37

Reduction: gain of electrons Oxidation:loss of electrons OILRIG

Question 38

What are electron shells

Answer 38

Shells are regarded as energy levels The energy increases as the shell number increases The shell number or energy level is called the principle quantum number

Question 39

What is an orbital

Answer 39

An atomic orbital is a region around the nucleus that can hold up to two electrons with opposite spin