par 2.3 using chemical formulas

• Science
• Middelbare school
• vwo
• Leerjaar 3

using chemical formulas

Atoms

Atoms are representated by an elementsymbol
.

Cl

H

H

O

O

C

C

O

H

Special elements ( di-atomic)

Claudia Fietst In Haar Ondergoed Naar Breda

Molecules of these atoms consists of two atoms.

-Br₂  : Bromine molecule

-I₂     : Iodine molecule

-N₂   : Nitrogen molecule

-Cl₂  : Chlorine molecule

-H₂   : Hydrogen molecule

-O₂   : Oxygen molecule

-F₂    : Fluorine molecule

 molecules

 Atoms can be combined to molecules

               CO₂                                                                                                          

 

Moleculedrawing

C

O

O

H

H

O

Index: the amount of atoms in a formula, index is in the formula

H₂O

chemical formulas

More molecules are represented by the coëfficiënt. This amount stands in front of the formula.

C

O

O

C

C

C

C

O

O

O

O

O

O

O

O

coëfficiënt 5

so 5CO₂

Assignment

How many molecules and atoms in the following formulas:

O₂

H₂O

4CH₄

7C₆H₁₂O₆

https:

Naming of substances

Systematic names 

Give the systematic name for:

P​2​​Cl​5​​

What is the formula for
(momo)-zwavel-tetra-bromide

1. S​4​​Br
2. SBr​4​​
3. SBr​5​​
4. SBr

2C​6​​Cl​5​​OH

Atomic mass and molecular mass 

The mass of atoms and molecules is very small.

The mass of a hydrogen atom is  1,68x10^-27 kg! 

Not very usefull to work with.

So that why : atomic mass unit  

1 u = 1,67x10-27 kg

Atomic mass en molecular mass

Atomic maas : Periodic table page 47 of your textbook 

Calculate moleuclar mass 

Sum of atomic mass of each seperate atom . 

So molecular mass for NaCl = 1 x 22,990 + 1 x 35,45 = 58,44 u

O (oxygen)

O₂

H₂O

AgCl

C₆H₁₂O₆

32

18

16

143,32

180,16 u

Calculate molecular mass for

KNO​3​​

Mass percentage of an element in a compound 

Calculate  m% C in CO

massa CO= 12,0 + 16,0

= 28,0

M% C = 12,0/28,0 x 100%

M%C = 42 %

Calculate mass percentage of O in

C​9​​H​8​​O​4​​

Par 2.3

read par 2.3, 

do q 2.3