d- and f-Block Elements · JEE Main previous year questions

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2020 8 questions

Q552020 · 6 Sept 2020 · Shift 1
The species that has a spin-only magnetic moment of $5.9 BM$ , is : ( $T_{d} = tetrahedral$ )
1. A. $[MnB r_{4}]^{2 -} (T_{d})$
2. B. $[NiC l_{4}]^{2 -} (T_{d})$
3. C. $Ni (CO)_{4} (T_{d})$
4. D. $[Ni (CN)_{4}]^{2 -} (square planar)$
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Answer: A
Q712020 · 3 Sept 2020 · Shift 2· Numerical answer
An acidic solution of dichromate is electrolyzed for 8 minutes using 2A current. As per the following equation $C r_{2} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2C r^{3 +} + 7 H_{2} O$ The amount of $C r^{3 +}$ obtained was $0.104 g$ . The efficiency of the process(in%) is (Take : $F = 96000 C$ , At. mass of chromium $= 52$ ) ____.
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Answer: 60
Q682020 · 2 Sept 2020 · Shift 2
Cast iron is used for the manufacture of :
1. A.wrought iron, pig iron and steel
2. B.wrought iron and pig iron
3. C.wrought iron and steel
4. D.pig iron, scrap iron and steel
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Answer: C
Q712020 · 2 Sept 2020 · Shift 2· Numerical answer
The oxidation states of transition metal atoms in $K_{2} C r_{2} O_{7}$ , $KMn O_{4}$ and $K_{2} Fe O_{4}$ , respectively, are x, y and z. The sum of x, y and z is _______.
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Answer: 19
Q642020 · 9 Jan 2020 · Shift 1
Complex X of composition $Cr (H_{2} O)_{6} C l_{n}$ has a spin only magnetic moment of 3.83 BM. It reacts with $AgN O_{3}$ and shows geometrical isomerism. The IUPAC nomenclature of X is :
1. A.Hexaaqua chromium (III) chloride
2. B.Tetraaquadichlorido chromium(IV) chloride dihydrate
3. C.Tetraaquadichlorido chromium (III) chloride dihydrate
4. D.Dichloridotetraaqua chromium (IV) chloride dihydrate
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Answer: C
Q742020 · 9 Jan 2020 · Shift 2· Numerical answer
The sum of the total number of bonds between chromium and oxygen atoms in chromate and dichromate ions is ____________.
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Answer: 18
Q742020 · 8 Jan 2020 · Shift 1· Numerical answer
Ferrous sulphate heptahydrate is used to fortify foods with iron. The amount (in grams) of the salt required to achieve 10 ppm of iron in 100 kg of wheat is _______. Atomic weight : Fe = 55.85; S = 32.00; O = 16.00
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Answer: 4.95 to 4.97
Q692020 · 7 Jan 2020 · Shift 1
The purest from of commercial iron is :
1. A.pig iron
2. B.wrought iron
3. C.cast iron
4. D.scrap iron and pig iron
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Answer: B