Analysis of the Earth and Environment Lecture 4: Water Chemistry Flashcards
Describe covalent bonding and the process of covalent bonding in water molecules(h20)
One oxygen atom, two hydrogen atom. The oxygen atom and the two hydrogen atoms share electrons in their outermost shell. Since electrons used in the covalent bond no longer contribute to the charge of the atom, and since the hydrogen atoms do not have any other electrons in their shell, the side of the molecule with the hydrogen atoms bonded has a slightly positive charge. Whilst the other side of the molecule where there is just the oxygen atom the charge is slightly more negative (as the oxygen atom has remaining electrons keeping its charge negative).
Water molecules have an uneven distribution of charge, each side of the molecule is either slightly positively charged or slightly negatively charged, What is the term for this?
These are called the polar regions of the molecule. Water molecules have permanent polar regions.
The oxygen side is the negative pole/δ−/Delta negative
The hydrogen side is the positive pole/δ+/Delta positive
Water is considered a universal solvent, what does this mean?
Since water molecules have a differing charge across their molecule, It is a universal solvent ( meaning it can dissolve more substances than any other liquid)
Describe the process of why and how ionic compounds dissolve in water
The process of ionic compounds dissolving in water is when the negatively charged pole/ oxygen atom side of the water molecule easily pulls cations away from the ionic lattice of the ionic compounds.
Whilst the positively charged pole/ hydrogen atom side easily pulls anions away from the ionic lattice of the ionic compound.
These two processes continue until all the ionic salt is dissolved.
Describe hydrogen bonding
In groups of water molecules, the negative pole/negatively charged oxygen side of molecule is attracted to the positive pole/hydrogen side of neighbouring water molecules.
These strong attractions/bonds are called hydrogen bonds
Describe the shape of a water molecule
Because the two lone electron pairs are closer to the oxygen atom, these exert a stronger repulsion against the two covalent bonding pairs, effectively pushing the two hydrogen atoms closer together.
The result of this is a distorted tetrahedral arrangement, in which the H-O-H angle is 104.5
O
/ \
H (104.5°) H
Why is water denser than ice (10% denser)and how does it relate to hydrogen bonding?
In ice/cooler temperatures, hydrogen bonds are more stable, they are not constantly breaking and reforming, as a result the oxygen atoms hold the hydrogen atoms rigidly at the 104.5° angle. Since all of the molecules are holding the hydrogen atoms at this angle, the molecules assume a crystal lattice with a hexagon shape.
Whereas in liquid water/ higher temperatures the hydrogen bonds become less rigid and they are regularly broken and reformed. As a result the molecules do not form a rigid lattice and are more tightly, randomly packed. Thus making them more dense.
Describe what an ionic compound is and explain the concept of when water is an ionic compound
An ionic compound is a chemical compound (which a positive or negative charge) created through a form of ionic bonding.
Occasionally when two water molecules collide, a hydrogen atom(H+) may be transferred between the two molecules.
Resulting in a hydronium ion(the ion which lost a hydrogen atom) and a hydroxide ion(the ion which gained a hydrogen atom).
Hydronium ion = OH-
Hydroxide ion = H3O+
Define a redox reaction
A redox reaction is a chemical reaction in which there is oxidation and reduction. Meaning that different atoms/ions/molecules in the chemical reaction are either gaining or losing electrons simultaneously.
