# Recent content by cloveryeah

1. ### Spectrum of Tandem MS

Homework Statement There are four scan modes for tandem MS: Product ion, Precursor ion, Neutral loss scan mode and MRM. e.g. In MRM, the result of graph is Intensity versus time, but NOT versus m/z. What does the "time" in the graph refers to? Homework Equations The Attempt at a Solution...
2. ### TLC Rf order

Homework Statement arrange the following eluents in an increasing order of Rf of aspirin ethyl acetate, n-hexane, n-butanol, methanol Homework Equations The Attempt at a Solution my order is n-hexane < n-butanol < ethyl acetate < methanol but the order is wrong. i am thinking: aspirin is...
3. ### Rank the acidity

Homework Statement BCl3, BF3, B(CH3)3, B(CH3O)3 Rank the acidity of these compounds. Homework Equations The Attempt at a Solution I dont know how to determine the acidity of B(CH3O)3 and how the acidity of BF3 and BCl3 is higher than B(CH3)3 because of F and Cl high electronegativity. How...
4. ### Recrystallization process

is it for the compound to have a better contact with the solvent?
5. ### Recrystallization process

In the mix solvent of recrystallization, why it is better to add the second solvent dropwise instead of by one-portion? i think...is it to improve the purification? but why?? is it increase the time of contacting the solvent so as to achieve a better dissolution??
6. ### Find local maximum value

Homework Statement y=(8/5)sint + (4/5) cost - (9/5)e^(-t/2) find its local max Homework Equations The Attempt at a Solution i have differentiated it and found out dy/dx, in order to find the local max, i have to find out the value t when dy/dx=0 but i cant solve this equation
7. ### Series converge or diverge

Homework Statement summation n from 1 to inf, 1/ln(n+5) converge or diverge Homework Equations The Attempt at a Solution 1/ln(n+5) > 1/n (from n=2 to inf) and i proved that it diverges by comparison test, am i correct? i am thinking that as my prove is n from 2 to inf not from 1 to inf...
8. ### Galvanic cell

Homework Statement A is an aqueous solution of KCl(aq) with unknown concentration. The following experiment was carried out at 25°C to determine the concentration of Cl- (aq) in A, and the Ksp of AgCl(s) Step 1: A half-cell was made by dipping a silver strip into 100.0 cm3 of A. Step 2: A...
9. ### Convergence or divergence

Homework Statement ∞ ∑ tan(1/k) k=5 show that it is convergent or divergent Homework Equations The Attempt at a Solution i used ratio test, but it's equal to 1, it means no works... i used divergence test, it equals to 0, no work too... so what should i do? i dont know how to use...
10. ### Summation series

Homework Statement ∞ Σ ( x^n/ln(n+5) ) n=1 find the value of x that the above series converges Homework Equations The Attempt at a Solution i cal. it by ratio test and i found that |x|<1 but when i input (-1,1) into my webwork...it said it's wrong[/B]
11. ### Calculate lim n->inf (n^2/n!)

lim→∞ 1/ [ (1⋅2⋅3⋅⋅⋅/n)(1-1/n)] = 1/0 = inf ??
12. ### Calculate lim n->inf (n^2/n!)

why not n / [1X2X3...(n-1)]
13. ### Calculate lim n->inf (n^2/n!)

what is wrong?
14. ### Calculate lim n->inf (n^2/n!)

Homework Statement calculate lim n->inf (n^2/n!) 2. Homework Equations The Attempt at a Solution i just calculated, and i got inf as the ans... n^2/1X2X3...Xn n/1X2X3...X(n-1) 1/[(1X2X3...)/n](1-1/n) when n->inf, it will go to inf am i correct? or there is something wrong?
15. ### Acid dissociation constant

Homework Statement when 10 cm3 of a monoprotic acid C3H6O3, with concentration of 7.2g/dm3, was titrated against against 0.05M NaCl, the equivalence point reached when 15.75cm3 (ph8) of NaOH was used. Calculate the acid dissociation constant Ka for C3H6O3. Homework Equations The Attempt at...