dyes

Question 1

cellulose fibres

Answer 1

amine groups (-NH2) enable dye molecules to form hydrogen bonds with cellulose fibres (cotton, rayon, linen) because these fibres contain lots of OH groups

Question 2

wool, silk and nylon

Answer 2

acidic groups like carboxylic acid or sulfonic acid (-SO3H) help dyes to bind to alkaline -NH- links
H+ ions move from dye to fibre molecule, and ionic interactions then hold them together

Question 3

ionic salt groups

Answer 3

-SO3NA
allow the dyes to bind with -NH- links
the salt groups dissociate when you dissolve the dye in water to give -SO3 - groups
to make the NH2+ groups, you need to add acid to provide H+ ions to the -NH- links. The SO3- groups will then bind to the -NH2+- links

Question 4

fibre reactive dyes

Answer 4

most permanent type of dye
have a functional group that will react with the OH of NH group in the fibre, forming strong covalent bonds

Question 5

chromophores

Answer 5

the structures in molecules that give them their colour

Question 6

what molecular features do chromophores contain?

Answer 6

double or triple bonds, lone pairs of electrons, benzene rings
usually form part of a delocalised electron system

Question 7

what functional group makes a dye more soluble?

Answer 7

SO3- Na+ (sulfate ion usually in the form of its sodium salt)