Chemistry - March 2007

A student weighs out 5.00 g of potassium iodide to react with an excess of lead II nitrate souliton. When the reaction is finished, weighs out the precipitate to a mass of 5.50 g. Calculate the student's percentage error. Help me with this one. Will be greatly appreciated.

2007-03-11 17:57:09 · 3 answers · asked by midian88 1

2007-03-11 17:45:25 · 5 answers · asked by substance 2

2007-03-11 17:43:57 · 1 answers · asked by substance 2

WRite a full chemical equation for tje reaction that would mark the end point for the reaction of the phosphoric acid with an aqueous soltion of sodium hydroxide using methyl violet indicator??

When a compund binds more strongly to the stationary phase that does what to the rf value??

A sample of Brass contains 64% copper by mass. zinc will react with the dilute acid but not copper. what volume of hydrogen gas would be expected to be formed at SLC when a 3.567g powered sample of brass is allowed to react with excess dilute hydrochloric acid??
(I have four alternatives for this answer so i can establish if ur well off or not))

Thanks heaps everyone... My tutor is struggling which is a worry, I know. If you can please show valid explanations to solutions

2007-03-11 17:41:24 · 2 answers · asked by mayeham7 1

2007-03-11 17:30:59 · 16 answers · asked by Anonymous

Kb = 1.10e-8

2007-03-11 17:16:36 · 1 answers · asked by alveenad 1

2007-03-11 17:11:10 · 6 answers · asked by jsjmlj 5

what is the temperature change of 100.0 ml of water when it absorbs 1365 joules of heat?

2007-03-11 17:01:53 · 3 answers · asked by Anonymous

A 25.00g sample of sodium carbonate-10-water was heated in an oven to remove all its water of crrystallisation. Calculate:
a) moles of sodium carbonate-10-water present in the original sample

Note: How do I do this? I just worked out the molar mass of sodium carbonate-10-water (Na2CO3.10.H2O) which=286.15
What is the answer? Do I need to refer to the 25.00g sample size? What do I do?

b) mass of water driven off in the oven
c) mass of anhydrous sodium carbonate remaining after heating

Please help me and show working before the answer. Thankyou.

2007-03-11 17:00:38 · 4 answers · asked by Anonymous

I really need help with this equation though

I have been crackin my noggin on this one. Thanks for looking.


Mo2O3 +(Mn2O4)1- ---------->>>>>MoO3 + (Mn2)1+

2007-03-11 16:53:56 · 2 answers · asked by Anonymous

which of the following statements are true?


a) For an acid H-A : the greater the electronegativity of A, the weaker the acid HA

b) For an acid H-A : the weaker the H-A bond, the stronger the acid H-A

c) HBr is a stronger acid than HF

d) H2SO3 is a weaker acid than H2SO4

e) HBrO is a stronger acid than HClO

f) For carboxylic acids : the smaller the electronegativities of the atoms in the group bonded to the carboxyl group, the stronger the acid

2007-03-11 16:53:47 · 4 answers · asked by joe p 1

identify the hybridization of the carbon atom(s) in Cl2CO

Also give the number of π bonds in the molecule or ion


An example of an answer would be:

sp3 2

2007-03-11 16:51:22 · 3 answers · asked by Ray W 1

Identify the hybridization of the central atom for both





ICl4- and ICl3





You give two answers here.
For example if the hybridization of the central atom for the first molecule or ion is sp3, and on the second is sp3d
you enter:
sp3 sp3d

2007-03-11 16:48:24 · 2 answers · asked by Ray W 1

Use the following letters corresponding to the molecular geometries to answer parts A. and B.


a) triangular planar b) tetrahedral



c) triangular pyramidal d) octahedral



e) triangular bipyramidal f) linear g) angular



A. What is the molecular geometry of a SiF6−2 molecule ?



B. Predict the molecular geometry of N2O

2007-03-11 16:46:14 · 3 answers · asked by Ray W 1

Use the following letters corresponding to the molecular shapes to answer part III and IV


a) triangular planar b) tetrahedral



c) triangular pyramidal d) octahedral



e) triangular bipyramidal f) linear g) angular



h) square planar i) seesaw



j) T shaped k) square pyramidal





For the molecule SbF5


I) How many lone pairs of electrons are on the central atom?


II) How many bonds (counting multiple bonds as one)
are on the central atom?


III) What is the molecular geometry of the molecule? (use the above letters


IV) What is the electron-pair geometry? (use the above letters)

2007-03-11 16:22:58 · 1 answers · asked by Ray W 1

I've searched alot I really need help.

2007-03-11 16:22:55 · 1 answers · asked by SinghisKing794 2

2007-03-11 16:20:57 · 3 answers · asked by Anonymous

a) For an acid H-A : the greater the electronegativity of A, the stronger the acid HA

b) For an acid H-A : the stronger the H-A bond, the stronger the acid H-A

c) HBr is a stronger acid than HF

d) H2SO3 is a weaker acid than H2SO4

e) HClO is a stronger acid than HBrO

f) For carboxylic acids : the greater the electronegativities of the atoms in the group bonded to the carboxyl group, the stronger the acid

2007-03-11 16:12:24 · 3 answers · asked by suraiya a 2

how many formula units are present in 9.71*10^-2 moles of NaF?
and how did you get the answer

2007-03-11 16:06:57 · 1 answers · asked by lynsey 2

2007-03-11 15:59:59 · 1 answers · asked by Teddy JJ 1

What is the Carbon -14 and what is its use?
Thanks!

2007-03-11 15:58:29 · 6 answers · asked by That girl... 6

A 9.54g sample of a compound containing only copper and oxygen was converted into copper by a reduction process involving hydrogen gas. The mass of the copper that remained after the reaction was 7.62g.
Determine
a) the empirical formula for the compound
b) if the relative formula mass of the substance is 79.55, what is its true formula and its proper name?

Note: Please help me answer these questions...I can't work out either a or b. Please explain the steps and processes involved if possible. Please be 100% certain of your answers and show working. Thanks

2007-03-11 15:57:14 · 2 answers · asked by Anonymous

how much heat is raised when 275 grams of water cools from 85.2 degrees C to 38.4 degrees C?

2007-03-11 15:56:12 · 2 answers · asked by Anonymous

2007-03-11 15:46:20 · 2 answers · asked by Anonymous

Heat can be considered a "product" in exothermic reactions.
If a reaction is endothermic and has a negative entropy change, we can assume that it is nonspontaneous.
If a reaction is exothermic and has a positive entropy change, we can assume that it is spontaneous.
If two moles of gas react to form one mole of liquid, we can assume that the reaction is spontaneous.

2007-03-11 15:28:24 · 5 answers · asked by Heavy Metal 3

most scientist thinks it's a chemical reaction (and can partially prove it) but others believe it occors naturally.

2007-03-11 15:16:50 · 7 answers · asked by Anonymous

A match burning
snow melting
sugar dissolving in water
water freezing

2007-03-11 15:02:44 · 4 answers · asked by Heavy Metal 3

2007-03-11 14:36:53 · 2 answers · asked by Anonymous

I have this lab to do, but I don't really understand. My question is what is the polarity of p-dichlorobenzene, silicon dioxide, and tin. Thanks.

2007-03-11 14:24:59 · 2 answers · asked by Anonymous

A compound that only contains the elemens nitrogen and hydrogen can be catalytically oxidised to form nitrogen gas and water. When a sample of this compound is completely oxidised by this process the mass of water formed was found to be 3.07g and the volume of dry nitrogen gas collected at SLC was 2.69L.
a) calculate the mass of nitrogen atoms present in this sample of the compound.
b) calculate the mass of hydrogen atoms present in this sample of the compund
c) determine the empirical formula for this compund.

2007-03-11 14:24:01 · 2 answers · asked by mayeham7 1