WAEC GCE CHEMISTRY ANSWER
*WAEC GCE CHEMISTRY THEORY ANSWERS*
*===========================*
*===========================*
(1a)
A solution of ammonia is basic, hence it turns red litmes blue.
(1bi)
Methylmethanoate.
(1bii)
A catalyst, concentrated tetraoxosulphate(vi) acid must be used to speed up the reaction.
(1ci)
CaC₂(s) + H₂0(l) —> C₂H₂(g) + CaO(s)
(1cii)
It is used in the production of oxy-acetylene flame used for welding.
(1d)
(i) Motarity
(ii) Masses
(iii) Saturation level.
(1e)
(i) Rusting requires moisture but burning does not.
(ii) Burning requires heat while rusting does not.
(1fi)
The K₂Cr₂O7 is reduced.
(1fii)
Hydrogen gas is geven off with the formation of iron(11) Chloride (green).
(1gi)
(i) Carbon(1V)Oxide, CO₂
(ii) Steam,
(iii) Heat energy
(1gii)
CxHy + (x + Y/A) —-> xC0₂ + y/₂ H₂0.
CH4 + 20₂ —-> CO₂ + 2H₂0
(1h)
Law of constant composition which states that equal volumes of all gases contain equal quantities of Particles at constant temperature and pressure.
*===========================*
*===========================*
(2a)
M=10g
M of CaCO3 = 40 + 12 + (3×16)
= 40 + 12 + 48
= 100g/Mol
n = Mass / molar mass
n = 10 / 100
n = 0.1 mole
(2bi)
2C₂H₂ + 2Na —> 2C₂HNa + H₂
(2bii)
C₂H5OH + Na —-> C₂H5ONa + H+
Na
(2c)
(SEE DIAGRAM ABOVE)
(2di)
Mg —> mg²+ + 2e-
2H+ + 2e- —> H₂(g)
(2dii)
Mg + 2H+ —> Mg²+ + H₂(g)
(2ei)
-TABULATE-
(CHOOSE ONLY TWO)
*UNDER MIXTURE*
(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
*UNDER COMPOUND*
(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
(2eii)
• An Element : Gold
• A Mixture : Soil
• A Compound : Quick Lime
*===========================*
“` TEAM CHEETAH “`?
*===========================*
(3ai)
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.
(3aii)
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.
(3aiii)
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.
(3aiv)
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.
*===========================*
*===========================*
(4a)
To determine the number of atoms in 10.0 g of CaCO3, we need to first convert the mass of the compound to moles using the molar mass of CaCO3, which is 100.09 g/mol.
10.0 g CaCO3 / 100.09 g/mol = 0.1000 mol CaCO3
We can then use Avogadro’s constant to convert the number of moles of CaCO3 to the number of atoms it contains.
0.1000 mol CaCO3 x (6.02 x 10^23 atoms/mol) = 6.02 x 10^22 atoms CaCO3
Therefore, there are 6.02 x 10^22 atoms of CaCO3 in 10.0 g of the compound.
(4b)
(I) C2H2 + 2 Na –> 2 NaH + C2H2
In this reaction, the sodium reacts with the hydrogen atoms in C2H2 to produce sodium hydride (NaH), which is a strong base. The resulting product is acidic due to the presence of hydroxide ions (OH-), which are produced when the alkali metal sodium reacts with the hydrogen atoms in C2H2.
(II) C2H5OH + Na –> NaOH + C2H5
In this reaction, the sodium reacts with the hydroxyl group (-OH) in C2H5OH to produce sodium hydroxide (NaOH), which is a strong base. The resulting product is acidic due to the presence of hydroxide ions (OH-), which are produced when the alkali metal sodium reacts with the hydroxyl group in C2H5OH.
(2a)
M=10g
M of CaCO3 = 40 + 12 + (3×16)
= 40 + 12 + 48
= 100g/Mol
n = Mass / molar mass
n = 10 / 100
n = 0.1 mole
(2bi)
2C₂H₂ + 2Na —> 2C₂HNa + H₂
(2bii)
C₂H5OH + Na —-> C₂H5ONa + H+
Na
(2c)
(SEE DIAGRAM ABOVE)
(2di)
Mg —> mg²+ + 2e-
2H+ + 2e- —> H₂(g)
(2dii)
Mg + 2H+ —> Mg²+ + H₂(g)
(2ei)
-TABULATE-
(CHOOSE ONLY TWO)
*UNDER MIXTURE*
(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
*UNDER COMPOUND*
(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
(2eii)
• An Element : Gold
• A Mixture : Soil
• A Compound : Quick Lime
CHEMISTRY OBJ
1-10: DABBBBABDC
11-20: BADBCCACAC
21-30: BAACBACAAA
31-40: BDADBAACBA
41-50: BACCBBACBC
(4ai)
(i) Carbon : A filter with granular activated Carbon is used to remove Certain chemical mostly Organic chemicals from water Carbon is used to remove com chemicals which gives Odors or taste to the water Such as Hydrogen Sulfide.
(ii) chlorine is added to water during treatment in order to kill Parasites bacterias and Viruses and the Process a Called chlorination
(4aii)
(i)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.
(ii)Filtration: Once the flocs have settled to the bottom of the water, the clear water on top is filtered to separate additional solids from the water. During filtration, the clear water passes through filters that have different pore sizes and are made of different materials (such as sand, gravel, and charcoal).
(iii) Disinfection: After the water has been filtered, water treatment plants may add one or more chemical disinfectants (such as chlorine, chloramine, or chlorine dioxide) to kill any remaining parasites, bacteria, or viruses.
