Q2: The stoichiometric reaction of 516 g of dimethyldichlorosilane with water results in a tetrameric cyclic product X in 75% yield. The weight (in g) of X obtained is _______.
[Use, molar mass (g mol−1):H = 1, C = 12, O = 16, Si = 28, Cl = 35.5 ] [JEE Advanced 2023 Paper 1]
Ans: 222
No. of moles = Given mass / Molar mass = 516 / 129 = 4
∴ Percentage yield = 75/100 = 0.75
∴ Mole formed of cyclic tetramer = 0.75
∴ Weight = 0.75 x 296 = 22g
Number of moles of sulphur precipitated (X) = 0.01
Mass of sulphur precipitates (X) = 0.01 × 32 = 0.32 gm
Q2: To check the principle of multiple proportions, a series of pure binary compounds (PmQn) were analyzed and their composition is tabulated below. The correct option(s) is(are):
(a) If empirical formula of compound 3 is P3Q4, then the empirical formula of compound 2 is P3Q5.
(b) If empirical formula of compound 3 is P3Q2 and atomic weight of element P is 20 , then the atomic weight of Q is 45 .
(c) If empirical formula of compound 2 is PQ, then the empirical formula of the compound 1 is P5Q4.
(d) If atomic weight of P and Q are 70 and 35 , respectively, then the empirical formula of compound 1 is P2Q. [JEE Advanced 2022 Paper 2]
Ans: (b) & (c)
(A) If emperical formula of compound 3 is P3Q4 then its molar ratio will be 40/3: 60/4
=40 / 3 × 4 / 60 = 16 / 18 = 0.88
If empirical formula of compound 2 is P3Q5, then its molar ratio
Since molar ratio of both the compound is not equal
So, option (A) is not correct.
(B) If empirical formula of compound 3 is P3Q2, i.e.,
and MP = 20 (given)
So, MQ / 20 = 9/4
MQ = 45
So, option (B) is correct.
(C) If empirical formula of compound 2 is PQ, So the molar ratio is
Empirical formula of compound 1 is P5Q4
so the molar ratio is 50/5 : 50/4.
= 50 / 5 × 4 / 50 = 4 / 5 = 0.8
Since, molar ratio of both the compound is equal hence, state (C) is correct.
So, option (C) is correct.
(D) MP = 70, MQ = 35
Molar ratio of compound 1 is
Hence, empirical formula of compound PQ2.
So, option (D) is incorrect.
M(NaOH) = 1/9
= 0.11
[∵ Moles of water = 900/18 = 50]
= 881.57 mL
Now, molarity
Number of moles of solute x 1000 / Volume of solution (in mL)
=
= 2.98 M
Q2: The amount of water produced (in g) in the oxidation of 1 mole of rhombic sulphur by conc. HNO3 to a compound with the highest oxidation state of sulphur is ..............
(Given data : Molar mass of water = 18 g mol−1) [JEE Advanced 2019 Paper 2]
Ans: 288
When rhombic sulphur (S8) is oxidised by conc. HNO3 then H2SO4 is obtained and NO2 gas is released.
1 mole of rhombic sulphur produces = 16 moles of H2O
∴ Mass of water = 16 × 18 (molar mass of H2O) = 288 g
(equation not balanced).
Few drops of concentrated HCl were added to this solution and gently warmed. Further, oxalic acid (225 mg) was added in portions till the colour of the permanganate ion disappeared. The quantity of MnCl2 (in mg) present in the initial solution is ____________.
(Atomic weights in g mol−1: Mn = 55, Cl = 35.5 ) [JEE Advanced 2018 Paper 2]
Ans: 126
Also,
Hence,
Oxalic acid taken = 225 mg
= 225 / 90
= 2.5 millimoles
Hence, MnCl2 = 1 millimole
= (55 + 71)
= 126 mg
352 videos|596 docs|309 tests
|
1. What are some basic concepts of chemistry covered in the JEE Advanced exam? |
2. How can I prepare for the basic concepts of chemistry for the JEE Advanced exam? |
3. What are some important topics related to the basic concepts of chemistry that I should focus on for the JEE Advanced exam? |
4. Are there any common misconceptions or traps to be aware of while studying the basic concepts of chemistry for the JEE Advanced exam? |
5. Can you suggest some online resources or study materials for the basic concepts of chemistry for the JEE Advanced exam? |
352 videos|596 docs|309 tests
|
|
Explore Courses for JEE exam
|