Class 12th

First, the number of unit cells in the given mass is determined. In an HCP structure, there are 6 atoms and 18 total voids (6 octahedral + 12 tetrahedral) per unit cell. Multiplying the number of unit cells by 18 gives the total number of voids. The result is14.9 x 10²¹, which is rounded.

Using the integrated rate laws for both reactions and solving for time 't' yields a value of 108.

Urea-formaldehyde resin is used for wood laminates because of its durable and unbreakable properties.

In proteins, the secondary structure (such as α-helices and β-sheets) is stabilized by hydrogen bonds formed between the carbonyl oxygen of one peptide bond and the amide hydrogen of another.

The magnetic moment of an ion is determined by its number of unpaired electrons (n). For the given lanthanide ions:

o   Ce? has 0 unpaired electrons (4f? ).

o   Eu³? has 6 unpaired electrons (4f? ).

o   Gd³? has 7 unpaired electrons (4f? ).
Gd³? has the highest number of unpaired electrons and therefore the highest magnetic moment.

Solubility of CdSO? is water ; S = 8 * 10? M
Using Ksp = S²
Ksp = 64 * 10? M
Now,
CdSO? Cd²? + SO? ²?
in H? SO? (0.01M)
Ksp = [Cd²? ] [SO? ²? ]
64 * 10? = S? (S? + 0.01)
S? << 0.01
So, S? = 64 * 10? M.

Moles of benzoic acid = 6.1 / 121 = 0.05
Theoretical moles of m- bromobenzoic acid = 0.05
Observed moles of m- bromobenzoic acid = 7.8 / 200 = 0.039
% yield = (0.039 / 0.05) * 100 = 78%

Half life, t? /? = 1min
Let, time of 99.9% completion of reaction be 't' min
Let the reaction is of first order
K = (2.303/t) log? ( [R]? / [R])
[R] = 0.001 [R]?
t = (2.303 * 3 min) / 0.693
t = 9.99 min
the nearest integer is 10.

λ° (BaCl? ) = 280 Scm²mol? ¹
λ° (H? SO? ) = 860 Scm²mol? ¹
λ° (HCl) = 426 Scm²mol? ¹
λ° (BaSO? ) = λ° (BaCl? ) + λ° (H? SO? ) - 2λ° (HCl)
= 280 + 860 - 2 * 426
= 288 Scm² mol? ¹