back to directory
NEET CHEMISTRYSome Basic Concepts of ChemistryMedium

Question

4.74 g of an inorganic compound contains 0.39 g of K, 0.27 g of Al, 1.92 g of SO4SO_4 radicals and 2.16 g of water. If molar mass of the compound is 948 g mol1948 \text{ g mol}^{-1}, the molecular formula of the inorganic compound is:

A

KAl(SO₄)₂·12H₂O

B

K₂Al₂(SO₄)₆·12H₂O

C

K₂SO₄·Al₂(SO₄)₃·24H₂O

D

K₂SO₆·Al₂(SO₄)₃·12H₂O

Step-by-Step Solution

  1. Calculate Moles of Constituents:
  • Moles of K = 0.3939=0.01 mol\frac{0.39}{39} = 0.01 \text{ mol}
  • Moles of Al = 0.2727=0.01 mol\frac{0.27}{27} = 0.01 \text{ mol}
  • Moles of SO4SO_4 = 1.9296=0.02 mol\frac{1.92}{96} = 0.02 \text{ mol}
  • Moles of H2OH_2O = 2.1618=0.12 mol\frac{2.16}{18} = 0.12 \text{ mol}
  1. Determine Empirical Formula: Divide by the smallest number of moles (0.01):
  • K : Al : SO4SO_4 : H2OH_2O = 1:1:2:121 : 1 : 2 : 12
  • Empirical Formula = KAl(SO4)212H2OKAl(SO_4)_2 \cdot 12H_2O
  1. Calculate Empirical Formula Mass: Mass=39+27+2(96)+12(18)=66+192+216=474 g mol1\text{Mass} = 39 + 27 + 2(96) + 12(18) = 66 + 192 + 216 = 474 \text{ g mol}^{-1}

  2. Determine Molecular Formula:

  • n=Molar MassEmpirical Mass=948474=2n = \frac{\text{Molar Mass}}{\text{Empirical Mass}} = \frac{948}{474} = 2
  • Molecular Formula = 2×[KAl(SO4)212H2O]=K2Al2(SO4)424H2O2 \times [KAl(SO_4)_2 \cdot 12H_2O] = K_2Al_2(SO_4)_4 \cdot 24H_2O
  • This can be rewritten in the standard double salt notation as: K2SO4Al2(SO4)324H2OK_2SO_4 \cdot Al_2(SO_4)_3 \cdot 24H_2O (Potash Alum).

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Some Basic Concepts of Chemistry. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYSome Basic Concepts of Chemistryinorganiccompoundcontainsradicalscompound

More Some Basic Concepts of Chemistry Questions

View all

At S.T.P. the density of $\text{CCl}_4$ vapour in $\text{g/L}$ will be nearest to:

A.$6.84$
B.$3.42$
C.$10.26$
D.$4.57$
MediumSolve

Calculate the mass of 95% pure $CaCO_3$ that will be required to neutralize 50 mL of 0.5 M HCl solution according to the following reaction: $$ CaCO_3(s) + 2HCl(aq) \rightarrow CaCl_2(aq) + CO_2(g) + 2H_2O(l) $$ [Calculate up to the second place of decimal point]

A.9.50 g
B.1.25 g
C.1.32 g
D.3.65 g
MediumSolve

The molar mass of a compound (X), whose $2.6 \text{ mol}$ weighs $312 \text{ g}$, is:

A.312 g mol⁻¹
B.120 g mol⁻¹
C.60 g mol⁻¹
D.811.2 g mol⁻¹
EasySolve

Calculate the mole fraction of the solute in a $1.00 \text{ m}$ aqueous solution.

A.0.177
B.0.771
C.0.0534
D.0.0177
MediumSolve

A compound X contains 32% of A, 20% of B and remaining percentage of C. Then, the empirical formula of X is: (Given atomic mass of A = 64; B = 40; C = 32 u)

A.ABC₃
B.AB₂C₂
C.ABC₄
D.A₂BC₂
EasySolve

When $50\text{ mL}$ of a $16.9\%\text{ (w/v)}$ solution of $\text{AgNO}_3$ is mixed with $50\text{ mL}$ of $5.8\%\text{ (w/v) NaCl}$ solution, then the mass of precipitate formed is: ($\text{Ag} = 107.8$, $\text{N} = 14$, $\text{O} = 16$, $\text{Na} = 23$, $\text{Cl} = 35.5$)

A.$28\text{ g}$
B.$3.5\text{ g}$
C.$7\text{ g}$
D.$14\text{ g}$
MediumSolve

The density of a $2 \text{ M}$ aqueous solution of $NaOH$ is $1.28 \text{ g/cm}^3$. The molality of the solution is: [molecular mass of $NaOH = 40 \text{ g mol}^{-1}$]

A.$1.20 \text{ m}$
B.$1.56 \text{ m}$
C.$1.67 \text{ m}$
D.$1.32 \text{ m}$
MediumSolve

How many moles of lead (II) chloride will be formed from a reaction between $6.5\text{ g}$ of $\text{PbO}$ and $3.2\text{ g}$ of $\text{HCl}$?

A.$0.044$
B.$0.333$
C.$0.011$
D.$0.029$
MediumSolve

This neet chemistry practice question is part of the TopperSquare free question bank. TopperSquare offers 15,000+ chapter-wise NEET MCQs across Physics, Chemistry, and Biology with detailed step-by-step explanations, full mock tests, NEET PYQs (2010–2024), and an AI-powered performance analytics dashboard. browse all neet practice questions → · practice chemistry sets →