For JEE 2025 Aspirants...
Doubt to nahi hai par chemical kinetics ke PYQs revise kar raha tha and I realised....
Is question ke liye ye
t₉₉ = 10 ⨯ t₁/₂ = 3 ⨯ t₉₀
t₁/₂ = 120 de rakha tha to
t₉₉ = 1200 ho gaya so
t₉₀ = 1200 / 3 = 400
But pata chala ki jin jin logo ne 400 mark kiya tha sablo -1 mila... So formula laga ke kar lena bas... yahi kehna tha...
7 Replies
@Dexter
Note for OP
+solved @user1 @user2... to close the thread when your doubt is solved. Mention the users who helped you solve the doubt. This will be added to their stats.this is first order according to r = k[A]
so t 1/2 = ln2 / K
=> K = ln2 / t(1/2)
putting t(1/2) as 120, you get K approx = 5.78 * 10^(-3)
or if you don't want to approximate that much then roughly 5.776 * 10^(-3)
t = ln(Ao/A) / K
for 90% decomposition, A = Ao / 10
so you get t = ln(10) / k = 2.303 / 5.776 * 10^(3)
after all of that i'm getting 398.71 which is roughly = 399
pretty ass question ngl
i'd skip and do it if i had enough time for 3 digit decimal precision at the very end
main formula lagane ke baad bhi ganda question hai
if i'd used 5.78 instead of 5.776 i would've gotten 398 as the answerthey should gave range
sad q
damn even w formula im gettig 400 ig my log values r less accuraye
+solved @Nimboi @iTeachChem @simplybear
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