# number

1. ### Quantum number at n=3 and l=2

Hello, From my understand, at n=3, it is possible to have l=2 (since the maximum l is n-1). However, at n=3, it think it is impossible to have l=2, since that is the d orbital, which only exists from n=4. Can someone explain this to me? It would be great if you can give an element that fits that...
2. ### Calculating number of moles from Keq

Hello, I am having trouble with a question on my lab report that is as follows: "Calculate the number of moles of reactants and products in an equilibrium mixture. Complete the ICE table below." I am given the Keq which is 3 and the initial amount of acid and alcohol which are (0.25/V) each...
3. ### Cannot grasp how to find number of moles & mass of a solute

I'm in week 2 of college chemistry and I am completely lost on how to work out one of my chapter problems. :confused: It's: Calculate the number of moles and the mass of the solute in each of the following solutions: (a) 325 mL of 8.23 × 10^−5 M KI, a source of iodine in the diet (b) 75.0 mL...
4. ### Number of Samples

The determination of iodine in sea water gave a mean value of 48.56 μg/L and a sample standard deviation ss of 1.35 μg/L. What is the minimum number of samples (N) which must be analyzed to have 95% confidence that the mean value differs from the true value by no more than 2.0%? n=? I'm...
5. ### What is the oxidation number of As in the compound K(NH4)2AsO4•6H2O?

What is the oxidation number of As in the compound K(NH4)2AsO4•6H2O? (A) –3 (B) +1 (C) +3 (D) +5
6. ### What is the number of molecules in 500 cm^3 of oxygen under room conditions?

And how do we solve this kind of problem?

The question goes like this: 10.0ml of a 0.1M K2Cr207 solution is added to 10.0ml of a 0.1M Pb(NO3)2 solution. What mass of PbCr207 is formed?? 0.1 = number and of moles of K2Cr207 divided by 0.01L, and number of moles is given mass divided by 294g/mol (molar mass), which gives 2.94g and with...
8. ### Determining number of atoms?

Had these 2 questions for chemistry homework and it is really frustrating me. Here is the information: The radius of an atom of gold (Au) is about 1.35 Angstroms, How many gold atoms would have to be lined up to span 9.0mm ? If the atom is assumed to be a sphere, what is the volume in cm^3 of a...
9. ### oxidation number quick help

Im finding oxidation numbers and am in a jam. N2O2 - find the oxidation number of N I worked it out giving a -4 for oxygen (-2 valence x 2 oxygen present) Then i needed something times 2 to balance the reaction to 0, and N only has -3 or +5 how could that work? The same goes for C4H10O, and...
10. ### QUICK HELP APPRECIATED! Numbering hydrocarbon branches

Hi! I've been given the alkane "3-ethyl-4-propylheptane". I found nothing wrong in the name, however, the 4-prefix (before propyl) is unnecessary since if the propyl would be sitting on ANY other carbon, the longest carbon chain would change and it would no longer be a heptane. My question is...
11. ### About oxidation number of halogens

when i can consider that oxidation number of halogens is +7 not -1 ???
12. ### Oxidation number of water

ok so i am trying to figure out this ion-electron method and so far no one has been able to help me figure out why in the equation K + H2O ----> KOH + H2 why does water have an oxidation number of 1? Shouldn't it be zero? thanks!