Waec Chemistry Answers 2022

Waec Chemistry Answers 2022

Here is the waec Chemistry Answers 2022

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Chemistry+Obj!

1ABACCABBCD

11DCDBCCDCDB

21BDCADAABCA

31CBDCCDCBBD

41CACCCDADCA

 

(5a)

(i) It melts to clear mobile liquid

(ii) A brownish gas is evolved.

 

(5bi)

(i) Carbon(ii)oxide

(ii) Lead(ii)oxide

 

(5bii)

Methane(CH₄)

 

(5biii)

(i) It leads to erosion

(ii) It causes pollution

 

(5biv)

This is because it has more surface area than it occupies leading to a faster rate of reaction.

 

(5bv)

Ammoniacal liquor

 

(5ci)

When water is added to white anhydrous CuSO₄ it turns blue.

 

(5cii)

(i) It removes the hardness by precipitating the trioxocarbonate(iv)

 

(ii) It removes the hardness by removing the calcium or magnesium ion and precipitating trioxocarbonate(iv).

 

(5ciii)

Ca(HCO₃)₂ → CaCO₃ + H₂O + CO₂

(3ai)

This can be defined as the number of atoms or molecules in one mole of a substance which is equal to 6.02 ×10²³

 

(3aii)

Mass/m.m = no. of molecules/Avogadro’s number

(2.30/m.m) × (3.01×10²²/6.02×10²³)

m.m = (2.30×6.02×10²³)/3.01×10²²

m.m = 46g/mol

 

(3aiii)

Since the molar mass = 46g/mol

The formula is NO₂

:. 14+(16×2)

14+32 = 46g/mol

:. NO₂

 

(3bi)

(i) There is no reaction but rather forms a layer underneath the water

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(ii) It reacts violently with water forming white silicon dioxide and hydrogen chloride gas.

 

(3bii)

The reaction is different because CCl₄ is an organic substance while SiCl₄ is not.

 

(3ci)

Extraction of copper

 

(3cii)

(i) CuSO₄

(ii) CuCl₂

 

(3ciii)

Cu²⁺ + 2e⁻ —> Cu

 

(3civ)

Using; m = ZIt

Z = m/It

Z = 3.2/(50x(3×60)+13)

Z = 3.2/(50×193)

Z = 3.2/9650

Z = 0.000332g/Asec

 

(3d)

[https://i.imgur.com/wnfOVYP.jpg]

 

Oxygen can be prepared by heating KClO₃ in the presence of manganese(iv)oxide which acts as a catalyst to produce KCl and oxygen gas. The reaction takes place at a lower temperature and much faster rate.

KClO₃ (MnO₂)heat—–> KCl + O₂

(2ai)

Ionization energy can be defined as the energy required to remove a loosely bound electron from the outermost shell of a gaseous covalently bonded atom.

 

(2aii)

This is because B has more shells than Be which makes the valence electrons to be far from the nucleus making it require less energy due to lesser nuclear attraction.

 

(2b)

I = 0.12A, t = 500seconds

m = 0.015g, F =96500C

M = 48.0, Charge = ?

Using;

m = MIt/CF

C = MIt/mF

C = (48×0.12×500)/(0.015×96500)

C = 2

 

(2ci)

Al₂O₃

 

(2cii)

(i) Electricity supply

(ii) Nearness to source of material

 

(2di)

This can be defined as a property of metal which are weakly attracted to an applied magnetic field

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(2dii)

(i) I → ₂₄Cr²⁺ → 2

₂₄Cr⁶⁺ → 0

 

(ii) ₂₄Cr²⁺

 

(iii) It has unpaired electrons.

*CHEMISTRY*

 

(1a)

(i)An acid is any compound which, in a chemical reaction is able to attach itself to an unshared pair of electrons in another molecule-a base, to form a new compound.

 

(ii)

Alcl₃

 

(1b)

Salting out is the process of adding concentrated sodium chloride solution to soap, to decrease the solubility of the soap. It consequently separates out as a hard cake on the surface or cooling.

 

(1c)

Reagent: {Ammonical solution of Silver trioxonitrate(v) [AgNo₃]}

Condition: {At room temperature}

 

(1d)

The percentage abundance of an isotope is the percentage of all naturally occurring atoms with a specific atomic mass of an element.

 

(1e)

(i)The element with atomic number 18 has electronic configuration 2,8,8. It has a completely filled valence shell. It is therefore inert. Hence it cannot have an oxide.

 

(ii)Being a covalent compound, the intermolecular forces between the Cl₂O molecules are weak and easily overcome.

 

(1f)

Add barium chloride solution to H₂SO₄ and HNO₃ separately. A white precipitate is formed in H₂SO₄ and no such precipitation is formed in HNO₃.

 

(1g)

(i)The main difference is that electrochemical cell does not need any external current for operation whereas electrolytic cells need external current to operate.

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(ii)Also, Oxidation occurs at the positive electrode and reduction at the cathode, in the electrolytic cell. While the reverse is the case in electrochemical cells.

 

(1h)

As we go down group 1 from top to bottom, it gets easier to remove the valence electron and form the positively charged cation. Hence group 1 elements increase in chemical reactivity as we go down the group

 

(1i)

Molecular formula is a chemical formula that gives the total number of atoms of each element in each molecule of a substance.

 

(1j)

(i)Ammonia, NH₃ will deviate more than hydrogen gas H₂

 

(ii)

-Ammonia have stronger intermolecular forces than H₂

-Ammonia has more volume than H₂ at the same concentration

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One Response

  1. abiola mayowa June 8, 2022

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