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...
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...
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...
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??
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
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...
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...
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...
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]
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?
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...
Homework Statement
integrate 1/(1+e^x) dx
Homework Equations
The Attempt at a Solution
firstly i let t=1+e^x
and then i come to : integrate 1/(t^2-1)
and then i put t=secx
.
.
.
but then the final ans is -1/2 ln | 2/e^x +1 |
it should be 1 instead of 2, i hv checked for the steps for so...
Homework Statement
1007n+1703m=1 when n and m are integers
Homework Equations
The Attempt at a Solution
i hv tried for so many times, but i cant find it
the GCD of 1007 and 1703 is 1, so it is possible to find n and m
Homework Statement
find the last digit of 3^101 X 7^202
Homework Equations
The Attempt at a Solution
i have cal. that the last digit is 7 by...:
[147]mod10 X ([3^4]mod10)^25 X ([7^4]mod10)^25 = [7]mod10 X [1]mod10 = [7]mod10
so the last digit is 7
is it correct?
Ka values of the 1st and 2nd dissociation of phthalic acid (HO2C-C6H4-CO2H) are
given below. Estimate the pH value for highest buffer capacity when a buffer is
prepared from 1:1 mixture of phthalic acid and sodium hydrogen phthalate (HO2CC6H4-
CO2Na) in water?
HO2C-C6H4-CO2H <=> H+...
Homework Statement
a boy is sliding down a curved slide, another boy with same mass is sliding down a straight slide. if both slides have the same height, which of them will reach the bottom first?
Homework Equations
The Attempt at a Solution
i m thinking if it is related to 1/2 mv^2 = mgh...
i m thinking of this...
area bounded by x=0, y=0, y=x^2, y=4-x^2 and x=2
why the region bounded by the below three cases are the same
1. x=0, y=0, y=x^2, y=4-x^2
2. y=0, y=x^2, y=4-x^2
3. and x=0, y=x^2, y=4-x^2
but after i add x=2 and compute the bounded region, it's different?
i am just...
if the centripetal force can be only provided by normal contact force.
centripetal velocity is Vs. If V<Vs, then it will lose contact of the road?
Or it will lose contact when n=0? Or when n<0?
THX