The chemical formula of a compound is a symbolic representation of its chemical composition. Chemical formulas reveal the elements that comprise a compound’s molecules, as well as the proportions in which the atoms of those elements combine to form those molecules. Quicklime and slaked lime have different proportions of atoms present in them.
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Definition: A chemical formula is a method of expressing information about the chemical quantities of atoms in a chemical compound or molecule using chemical element symbols, numbers, and other symbols such as dashes, parentheses, commas, brackets, and plus (+) and minus (-) signs. |
Write the chemical formula of quicklime and slaked lime questions Chemistry Questions with Solutions
Q-1: The chemical name of slaked lime is
a) Calcium oxide
b) Calcium hydroxide
c) Magnesium oxide
d) Magnesium hydroxide
Answer: b) Calcium hydroxide is the chemical name of slaked lime.
Q-2: What is another term for slaked lime?
a) Caustic lime
b) Lime water
c) Hydrated lime
d) All of the above
Answer: d) All of the above
Explanation: Calcium hydroxide, also known as caustic lime, hydrated lime, builders’ lime, slaked lime and pickling lime.
Q-3: CaO is the empirical formula for calcium oxide. Determine the oxygen percentage by mass in this compound. Atomic weights: Ca= 40 g/mol, O = 16 g/mol
Answers:
Q-4: Which of the following is the correct chemical formula for quick lime?
a) Ca(OH)2
b) CaO
c) Na2O
d) NaOH
Answer: b) CaO
Explanation: CaO is the correct chemical formula for quick lime.
Q-5: How many grams of hydrogen are present in 2 moles of slaked lime?
Answer: The chemical formula for slaked lime is Ca(OH)2.
1 mole of Ca(OH)2 contains 2 Hydrogen atoms
2 moles of Ca(OH)2 contains 4 Hydrogen atoms
1 atom of hydrogen has a mass of 1g.
Thus, 4 hydrogen atoms will have a mass of 4g.
Q-6: In the reaction
CaCO3 + heat → A + CO2
a) Predict A and the valency of atoms present in it.
b) Identify the name of A
Answer:
a) The reaction is: CaCO3 + heat → CaO + CO2
Thus, A is CaO.
The charge on the atoms in the compound is referred to as valency. Calcium is in the +2 oxidation state (charge) and O is in the -2 oxidation state in the compound CaO. As a result, the valency of both atoms is 2.
b) The name of A is calcium oxide or quicklime.
Q-7: Match column I with column II
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Column I |
Column II |
|---|---|
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A) Milk of magnesia |
i) NaOH |
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B) Slaked lime |
ii) NaHCO3 |
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C) Caustic Soda |
iii) Ca(OH)2 |
|
D) Baking Soda |
iv) CaO |
|
E) Quick lime |
v) Mg(OH)2 |
Answers: A)-v), B)-iii), C)-i), D)-ii) , E)-iv)
Q-8: How much slaked lime would be needed to completely decompose 8 grams of ammonium chloride?
Answer: The equation representing the decomposition of NH4Cl by slaked lime, that is, Ca(OH)2 is
Ca(OH)2 + 2NH4Cl → CaCl2 + 2NH3 + 2H2O
Molar mass of Ca(OH)2 = 74 g
Molar mass of NH4Cl = 107 g
From the above equation, we can see that
107 g of NH4Cl are decomposed by 74 g of Ca(OH)2
8 g of NH4Cl are decomposed by Ca(OH)2 = (8×74)/107 = 5.53 g
Q-9: Quick lime contains
a) only covalent bonds
b) only ionic bonds
c) one covalent and one ionic bond
d) one ionic and one coordinate bond
Answer: b) only ionic bonds
Explanation: In quick lime(CaO), Ca2+ ion is bonded to O2- via an ionic bond. It is an ionic compound.
Q-10: The Ca2+ ion constituent in quicklime’s chemical formula is isoelectronic with
a) Chlorine
b) Neon
c) Argon
d) Potassium
Answer: c) Argon
Explanation: There are 18 electrons in the Ca2+ ion. Argon is the only element in here with 18 electrons. As both have the same number of electrons,therefore they are isoelectronic species.
Q-11: Write the atomicity of different constituent ions in slaked lime’s chemical formula.
Answer: Slaked lime contains the constituent ions OH– and Ca2+. Ca2+ is a monatomic cation because it only has one atom, whereas OH– is a diatomic anion because it has two atoms- oxygen and hydrogen.
Q-12: The chemical formula for slaked lime is Ca(OH)2. How many electrovalent bonds does it contain?
Answer: Ca+2 ion form one ionic bond with each OH– ion in slaked lime. Thus it contains two electrovalent bonds(ionic bonds).
Q-13: When one mole of calcium phosphide reacts with an excess of water, it produces
a) 1 mol of slaked lime
b) 2 mol of phosphine
c) 3 mol of slaked lime
d) 1 mol of phosphoric acid
Answer: c) 3 mol of slaked lime
Explanation: The balanced chemical reaction between calcium phosphide(Ca3P2) and excess of water is
Ca3P2 +6H2O → 3Ca(OH)2 +2PH3
Hence, we can clearly see that 3 moles of Ca(OH)2( slaked lime) are formed.
Q-14: Is quick lime hygroscopic in nature? If yes, write the reaction involved?
Answer: Yes, quick lime is hygroscopic in nature. It readily absorbs moisture from the environment. The reaction involved is:
CaO + H2O → Ca(OH)2
Q-15: Milk of lime is formed when slaked lime is added in water. It is a
a) Mixture
b) suspension
c) Colloid
d) Homogenous mixture
Answer: b) suspension
Explanation: When slaked lime is added to water it forms a suspension called milk of lime.
Practise Questions on Write the chemical formula of quicklime and slaked lime
Q-1: Slaked lime is a
a) covalent compound
b) Ionic compound
c) coordinate compound
d) coordination compound
Q-2: In the chemical formula of the quick lime, CaO, the O2- ion is
a) polyatomic
b) Monoatomic
c) diatomic
d) triatomic
Q-3: Calculate the amount of slaked lime required to remove the hardness of 60,000 litres of well water which has been found to contain 1.62 g of calcium bicarbonate per 10 litre.
Q-4: Which of the following has the largest number of oxygen atoms?
1 mole of quick lime or 1 mole of slaked lime
Q-5: Which of the following correctly represents the cation, anion and chemical name of quick lime?
a) Ca2+ , OH2-, calcium dihydroxide
b) Ca2+, O22-, calcium oxide
c) O22-, Ca+, dioxycacide
d) Ca2+,O2-, calcium oxide
Click the PDF to check the answers for Practice Questions.
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