WAEC GCE CHEMISTRY OBJ;-ExamgrandComNg
A solution of ammonia is basic, hence it turns red litmes blue.
A catalyst, concentrated tetraoxosulphate(vi) acid must be used to speed up the reaction.
CaC₂(s) + H₂0(l) —> C₂H₂(g) + CaO(s)
It is used in the production of oxy-acetylene flame used for welding.
(iii) Saturation level.
(i) Rusting requires moisture but burning does not.
(ii) Burning requires heat while rusting does not.
The K₂Cr₂O7 is reduced.
Hydrogen gas is geven off with the formation of iron(11) Chloride (green).
(i) Carbon(1V)Oxide, CO₂
(iii) Heat energy
CxHy + (x + Y/A) —-> xC0₂ + y/₂ H₂0.
CH4 + 20₂ —-> CO₂ + 2H₂0
Law of constant composition which states that equal volumes of all gases contain equal quantities of Particles at constant temperature and pressure.
M of CaCO3 = 40 + 12 + (3×16)
= 40 + 12 + 48
n = Mass / molar mass
n = 10 / 100
n = 0.1 mole
2C₂H₂ + 2Na —> 2C₂HNa + H₂
C₂H5OH + Na —-> C₂H5ONa + H+
(SEE DIAGRAM ABOVE)
Mg —> mg²+ + 2e-
2H+ + 2e- —> H₂(g)
Mg + 2H+ —> Mg²+ + H₂(g)
(CHOOSE ONLY TWO)
(i) Homogenous in Nature
(ii) Mixed in any proportion
(iii) Components that make up a mixture can be separated by any physical means
(iv) Does not have a chemical Formula
(i) May be Homogeneous Or Heterogeneous
(ii) Elements or components are in simple whole number ratio
(iii) Elements that make up a compound cannot be separated by any physical means
(iv) It has a chemical Formula
• An Element : Gold
• A Mixture : Soil
• A Compound : Quick Lime
Atoms are modified when they undergo chemical reactions or when they are combined with other atoms to form new compounds or molecules. In a chemical reaction, atoms can gain or lose electrons, forming ions, or they can share electrons to form chemical bonds with other atoms. When atoms combine to form compounds or molecules, they are modified by the formation of these new structures, which have different chemical properties than the individual atoms that make them up.
The resulting compounds have different chemical properties than the individual atoms that make them up, so they are considered to be modified versions of the atoms that compose them. For example, when hydrogen and oxygen atoms combine to form water, the resulting compound has different chemical properties than the individual atoms, such as a different boiling point and different reactivity with other chemicals.
Atoms of the same element can be modified by gaining or losing electrons, which changes their chemical properties. For example, an atom of sodium can lose an electron to become a sodium ion with a positive charge, while an atom of chlorine can gain an electron to become a chlorine ion with a negative charge. These ions have different chemical properties than the neutral atoms they were derived from. Additionally, atoms of the same element can be modified by forming chemical bonds with other atoms to create compounds or molecules, which have different chemical properties than the individual atoms that make them up.
While atoms can be modified by undergoing chemical reactions or by forming chemical bonds with other atoms to create compounds or molecules, the fundamental building blocks of these new structures are still atoms. The atoms themselves are not destroyed or created in these processes, they are simply rearranged or combined in different ways. This is the basis of the law of conservation of mass, which states that mass can neither be created nor destroyed in a chemical reaction.
X = RCLO3
I = petroleum refining
I = Sugar refining
II = Garring production
I = Magnetism
= Mettalic Solid
II = Size of particles
= Solid at room Temperature
III = Boiling
n = Mass / Molar Mass
n = 11/12
n = 0.92Mol
Number of Molecules = No of moles x Avogadro’s number
= 0.92 × 6.02 × 10²³
= 5.54 ×10²⁵ molecules
A mole is 22.4dm³
0.92mole = xdm³
X dm³ = 22.4 × 0.92
= 20.6 dm³
(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
(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.
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.
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
Acid rain can ruin buildings and statues by stripping away the material and corroding metal that makes up these structures.
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
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.
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.
(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.
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.
(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.
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