Chemistry - November 2007

MnO has either the NaCl type structure or the CsCl type structure. The edge length of the MnO unit cell is 4.47*10^-8 cm and the density of MnO is 5.28 g/cm^3.
a) Does MnO crystalize in the NaCl or CsCl structure?
b) assuming that the ionic radius of oxygen is 140 pm. estimate the ionic redius of manganese.

For the structures it refered mo to this question....The CsCl structure is a simple cubic array of chloride ions with a cesium ion at the center of each cubic array. Given that the density of cesium cholride is 3.97 g/cm^3 and assuming that the chloride and cesium ions touch along the body diagonal of the cubic unit cell. calculate the distance between the centers of adjacent Cs+ and Cl- ions in the solid. Compare this value with the expected distance based on the sized of the ions. The ionic radius of Cs+ is 169 pm and the ionic radius of Cl- is 181 pm.

Thanks im trying to review and don't know what to do for this one...if you could help it would be great :]

2007-11-15 15:45:36 · 2 answers · asked by kayedge27 2

2007-11-15 15:31:02 · 1 answers · asked by Anonymous

Given these equations in order:
4MnSO4 + 8KOH --> 4Mn(OH)2
4Mn(OH)2 + O2 + H2O --> 4Mn(OH)3
4Mn(OH)3 + 6H2SO4 --> 2Mn2(SO4)3 + 12H2O
2 Mn2(SO4)3 + 4 KI --> 4MnSO4 + 2K2SO4 + 2I2
2I2 + 2I- --> 2I3-
3Na2S2O3 + 2I3- --> Na2S4O6 + 4 Na+ + 6 I-

and given Molarity of Na2S2O3 is .0000855 mol/L, how many moles of O2 are present?

Tell me what stoichiometry steps to work with this please!

2007-11-15 15:24:42 · 1 answers · asked by Anonymous

What factors in foods affects its amount of calories?

2007-11-15 15:20:27 · 1 answers · asked by sophesticatedsophia 1

2007-11-15 15:20:23 · 1 answers · asked by Anonymous

2007-11-15 15:18:57 · 4 answers · asked by Anonymous

every site online talking about this is 99% some school thing

i'm good with math and it's probably incredibly simple
but
i don't understand how to turn absorbance vs time data into usable information
every thing i read on it lightly talks about it and then goes straight to the other equations
i've yet to see what exactly they are doing with this

i'm pretty sure i believe it has something to do with the slopes
but i need to actually see it done out in as many steps

i don't know why it's mystifying me so much
i know for nonlinear plots i should find the tangent buti was told just find the slope at a flat point haha
but a 2nd order regression line fits perfect and i wouldn't mind relating that into it
but
first things first
my retardedness at seeing the connection beyond this

2007-11-15 15:08:56 · 1 answers · asked by Anonymous

....representitive elements

2007-11-15 15:05:58 · 1 answers · asked by tinygirl0207 1

A couple of problems I couldn't get on my homework. Any help appreciated!!

Write rxn like this: Ox(1) + Red(2) + other -> Red(1) + Ox(2) + other

1. Write net equation for the spontaneous redox reaction and determine the standard cell potential that results when each of the following redox couples are connected in an electrochemical cell.

a. H1+/H2 and Cu2+/Cu E˚ =
b. Cr/Cr3+ and Ag1+/Ag E˚ =

2. Write net equations for the spontaneous redox reactions that occur during the following:

A copper wire is added to nitric acid

2007-11-15 14:37:18 · 1 answers · asked by crazygirl0630 2

I know N is +5
and O is -2

But why? I mean, there are 3 O's, so that'd be -6 right? And why is N +5?

2007-11-15 14:36:42 · 1 answers · asked by Caramel 2

2007-11-15 14:31:55 · 4 answers · asked by Song Cry 2

es para quimica...
me lo dejaron d tarea y no lo encuentro..

podria ser permaganato potasico de calcio?

2007-11-15 14:29:59 · 1 answers · asked by Anonymous

AP chemistry question- thermal energy

2007-11-15 14:23:48 · 4 answers · asked by chaniquana 1

Chemistry and Percent yield...can anyone help?
1.LiOH + CO2 → Li2CO3 + H2O

If the percent yield of the above reaction is found to be 92.52 %, how many grams of Li2CO3 are produced from the complete reaction of 88.02 g of CO2 ?

2.What is the percentage of sulfur in NiSO4 by mass ?

3. 65.45 % C
5.49 % H
29.06 % O

4.13 g of the compound fills a 179.0 ml bottle with a pressure of 2593.4 mm Hg at a temperature of 24.6oC. What is the molecular formula of this compound ?

4.
A certain compound was found to have a molar mass of 74.122 g. A 1.512 g sample of this compound was burned in pure oxygen gas. The measured amount of CO2 produced was 3.591 g, while that of H2O was 1.837 g. No other products were produced in the reaction. How many moles of carbon were in the original sample that underwent combustion ?

2007-11-15 13:25:52 · 2 answers · asked by matt b 1

LiOH + CO2 → Li2CO3 + H2O



If the percent yield of the above reaction is found to be 92.98 %, how many grams of Li2CO3 are produced from the complete reaction of 119.75 g of LiOH ?

2007-11-15 12:46:35 · 2 answers · asked by done 2

Two substances, W and X, react to form the products Y and Z. The following data shows the # of moles of the reactants and products involved. Use the data to determine the coefficients that will balance the equation:

W + X => Y + Z

Reaction Data:
Moles of reactants -- W: 0.90, X: 0.30
Moles of products -- Y: 0.60, Z: 1.20

2007-11-15 12:41:33 · 4 answers · asked by jacobib713 1

2007-11-15 11:50:38 · 4 answers · asked by Anonymous

2007-11-15 11:28:43 · 2 answers · asked by Ramaswamy S 2

thnx.

2007-11-15 11:11:05 · 2 answers · asked by Jessica 3

2007-11-15 11:06:55 · 1 answers · asked by Jessica 3

TeCl4
(IF4)-
(PtCl4) 2-
XeF4
SeF4

2007-11-15 10:49:01 · 1 answers · asked by mightyfiiiine 1

2007-11-15 10:20:29 · 5 answers · asked by jr 1

i have electricity class and have problem answering these questions please help me the chapter were on is Sources of electricity , Chemical Energy

6) DC is an abbreviation for ___________________

7) As discussed in previous units Electrons travel from _____________ to ______________


8)The flow of electrons in a circuit is called ______________


9) Childern's toy, cell phone use _________________
as a source of electricity.

10)An instrument used to test for broken wires or burned out (open) fuses in ___

2007-11-15 10:18:05 · 4 answers · asked by babygirl 1

A weather balloon has a volume of 52.5 liters at a temperature of 295K. The balloon is released and rises to an altitude where the temperature is 252k.

2007-11-15 10:15:17 · 1 answers · asked by Anonymous

Dear Yahoo Answers,
This is a really hard chem question and I am having difficulty with it. Please Help.

An Acid spill involves 2000 Litres of HCl solution that has a concentration of 6 moles of HCl per litre. Solid Ca(OH)2 is used to neutralize the spill. Calculate the mass of the calcium hydroxide required to do the job according to the equation;
Ca(OH)2 +2HCl = 2H2O + CaCl2 (4 marks)

I really need to figure this out and see the process that needs to be taken so any contribution will be appreciated.

Thanks.

2007-11-15 10:12:29 · 2 answers · asked by Anonymous

Chemistry: Multiple Choice Help?
Hello. I need help with the following Chemistry Multiple Chocie Questions. Culd you help me please.

The following information is related to questions 7, 8 and 9.
25 grams of calcium carbonate is treated with excess hydrochloric acid and the reaction is described by the following equation:

CaCO3 +2HCl = CO2 + H2O + CaCl2

7) The number of moles of hydrochloric acid consumed is:
a) 0.10
b)0.25
c)0.50
d)0.75
e)1.00

8) The volume of CO2 formed at STP is
a)2.8L
b)5.6L
c)11.2L
d)22.4L
e)44.8L

9) The mass of water produced is:
a) 4.5 Grams
b)9.0 Grams
c) 18.0 Grams
d) 36.0 Grams
e)50.0 Grams


Any Contribution will be appreciated. Thanks.

2007-11-15 10:09:24 · 1 answers · asked by Anonymous

My AP Chem teacher gave us this assignment to do, and i don't know how to do it, so help me please.

The assignment says:
"The best buffers consist of half-neutralized weak acid. When that happens the buffer can resist the greatest amount of added acid or base, and pH=pKa, as shown in the H-H equation.

However, fairly effective buffers can be made where [A-]/[HA] is not exactly 1.00, but farily close (0.20-5.00).

Your task is to select an appropriate weak acid and give directions to make one liter of buffer that will have a pH equal to a given value.

Your buffer can be 0.5-1.0M HA with and appropriate amount of A-."

The pH value given to me was 6.00

Please help me do this.

2007-11-15 09:42:51 · 1 answers · asked by Curtis D 1

of an atom which has half as many protons as Si (mass no. 28) and 6 fewer neutorns than atom of Si (mass no 28).

Give symbol, mass no, and atomic no

2007-11-15 09:39:14 · 2 answers · asked by Anonymous

and what would the electron configuration look like? well even if you can only the first question that would help thanks

2007-11-15 09:35:37 · 7 answers · asked by rst41 2

2007-11-15 09:16:17 · 2 answers · asked by mightyfiiiine 1