Waec gce chemistry 2023 Questions and Answers

Waec gce chemistry 2023 questions and answers

(4ai)
(i) Carbon: A filter with granular activated carbon is used to remove certain chemical mostly Organic chemicals which gives odor or taste to the water, such as Hydrogen Sulfide.
(ii) Chlorine: This is added to water during treatment in order to kill parasites, bacterias and viruses. This process is called chlorination

(4aii)
(i) Coagulation: Coagulation is often the first step in water treatment. During coagulation, chemicals with a positive charge are added to the water. The positive charge neutralizes the negative charge of dirt and other dissolved particles in the water. When this occurs, the particles bind with the chemicals to form slightly larger particles. Common chemicals used in this step include specific types of salts, aluminum, or iron.

(ii) Flocculation
Flocculation follows the coagulation step. Flocculation is the gentle mixing of the water to form larger, heavier particles called flocs. Often, water treatment plants will add additional chemicals during this step to help the flocs form.

(iii) Sedimentation: Sedimentation is one of the steps water treatment plants use to separate out solids from the water. During sedimentation, flocs settle to the bottom of the water because they are heavier than water.

(4bi)
When humans burn fossil fuels, sulfur dioxide (SO2) and nitrogen oxides (NOx) are released into the atmosphere. Those air pollutants react with water, oxygen, and other substances to form airborne sulfuric and nitric acid. These pollutants causes acid rain

(4bii)
Acid rain can ruin buildings and statues by stripping away the material and corroding metal that makes up these structures.

(4ci)
Allotropy is the existence of a chemical element in two or more forms, which may differ in the arrangement of atoms in crystalline solids or in the occurrence of molecules that contain different numbers of atoms

(4cii)
In a graphite molecule, one valence electron of each carbon atom remains free, Thus making graphite a good conductor of electricity. Whereas In diamond, they have no free mobile electron. That is why diamond are bad conductor electricity.

(4ciii)
Animal Charcoal

(4di)
Water is called a 'universal solvent' because water can dissolve much more substances than any other liquid found in nature but water cannot dissolve every substance.

(4dii)
(Pick Any TWO)
(i) Hard water is unfit for washing as it is difficult to form lather with soap.
(ii) Scum may form in a reaction with soap, wasting the soap.
(iii) Furring of tea kettles will take place due to the formation of carbonates of calcium and magnesium.

(4diii)
Due to hydrogen bonding in water which is not in Hydrogen sulphide, water will have the stronger intermolecular force and hence, more temperature will be required to boil it.

(4div)
(Pick Any ONE)
(i) It is used in the production of Ammonia by producing hydrogen.
(ii) It is used in welding and glass making.
(iii) It is used for several organic compound synthesis in industries like the production of several hydrocarbons.
(iv) Water gas helps in the removal of Carbon dioxide from fuel cells.