Chemistry - Periodic table

bonkysleuth SG

you are provided with the following substances.

magnesium metal
copper metal
aqueous chlorine
aqueous iodine
aqueous copper (II) sulphate
aqueous magnesium nitrate
aqueous potassium chloride
aqueous potassium iodide

use substances from the list to show that

(i) copper is less reactive than magnesium.

include details of observation.

I ain’t sure how to go about doing this. can someone help? thanks. =)))

FirePig SG

more reactive one will becomes ions. Less reactive one becomes the metal.

So judging from the list you get, use

copper (2) sulphate + magnesium metal ---> magnesium sulphate + copper metal

bonkysleuth SG

thanks.

by the way do you know how to know an ionic equation from lead carbonate and hydrochloric acid reaction?

is the charge for lead 2?

if thats the case, shouldnt you get

PbCO3 (s) + HCl (aq) -> CO2 (g) + H2O (l) + PbCl2 (s)

you can't cancel anything from this! did i make a mistake somewhere? even if i get the charge correct, the equation stil cant be cancelled. for carbonates, sodium, potassium and ammonium and mostly grp 1 metals are soluble while the rest are not. so i'm pretty sure PbCO3 is insoluble. and only Pb2+ and Ag+ are insoluble in halogen compounds of halide solutions. so PbCl is insoluble too. is there anything wrong?

secondly, the ionic equation for sulphuric acid and calcium hydroxide.

H2SO4 (aq) + Ca(OH)2 (aq) - > H2O(l) + Ca(SO4) (s)

cant cancel anything from this equation too... strange. by the way, my tb says Ca(OH)2 is soluble in water while my notes say only grp 1 (alkalis metals) hydroxides are soluble in water. i'm confused by all these! can someone clarify?

next, basic oxides are said to be mostly insoluble in water with the exception of other metal oxides like sodium potassium, etc. but calcium oxide dissolves in water to form calcium hydroxide. so does this mean substance that are insoluble in water doesn't mean they cant react in water?

i'm rather addled by all these. god damn confusing. please help!

Oceane SG

thanks.

by the way do you know how to know an ionic equation from lead carbonate and hydrochloric acid reaction?

is the charge for lead 2?

if thats the case, shouldnt you get

PbCO3 (s) + HCl (aq) -> CO2 (g) + H2O (l) + PbCl2 (s)

secondly, the ionic equation for sulphuric acid and calcium hydroxide.

H2SO4 (aq) + Ca(OH)2 (aq) - > H2O(l) + Ca(SO4) (s)

i'm rather addled by all these. god damn confusing. please help!

2nd equation: Neutralization reaction.

So ionic equation should be the formation of water.

ALL carbonates are insoluble except your Group I carbonates.

SPCA hydroxides are soluble.

Darkness_hacker99 SG

Lead(II) carbonate reaction with Hydrochloric Acid to produce Carbon dioxide, Water and Lead(II) Chloride.

Your equation got careless mistake.--> You left out the coefficient for HCl..

It's:

PbCO3 (s) + 2HCl (aq) -> CO2 (g) + H2O (l) + PbCl2 (s)

What you explained are correct.

The ionic equation for this reaction is:

PbCO3 (s) + 2H+ 2Cl- (aq) -> CO2 (g) + H2O (l) + PbCl2 (s)

Why? Cos the Carbonate ions will accept 2 H+, to form carbonic acid, which decomposes to carbon dioxide, water, and lead(II) chloride is insoluble.

Probability of O level coming out this question is almost zero.

bonkysleuth SG

more reactive one will becomes ions. Less reactive one becomes the metal.

So judging from the list you get, use

copper (2) sulphate + magnesium metal ---> magnesium sulphate + copper metal

thanks guys for trying to explain. But Oceane i still don't get the part about calcium hydroxide being a substance in aqueous state. can anyone elaborate ?

wishboy SG

Calcium hydroxide, Ca(OH)2, is an alkali, meaning it is a soluble base, which makes it aqueous
is tat wad u trying to ask?

bonkysleuth SG

o, and i ain't sure about how to determine the oxidation state of oxygen in a particular compound, etc.

take for example superoxide.

in KO2. the oxidation state is -1.

and for Na2O2, think its peroxide blah. the oxidation state is -1 too. this i understand through a series of mathematical statement. i just cant deduce the oxidation state by mere glance at the formulae.

I got the answer for Na2O2 through :

Na has a charge of +1. take oxidation state of O as X

2(+1) + 2(X) = 0

the 2 in the first part refers to the sodium atoms while the 2 before the X refers to the oxygen atoms. can someone help me look whether this method is correct in deriving the answer?

the answer's 0 cuz we needa balance the charge.

2+2(-1) = 0

so the oxidation state is -1 then. but i can't get the answer using this for superoxide oxidation state - KO2.

ooo, and lastly, ions formulae for superoxide (KO2) is O2 -. don't understand this part. the 2 is written at the bottom of the O as a subscript.

bonkysleuth SG

Calcium hydroxide, Ca(OH)2, is an alkali, meaning it is a soluble base, which makes it aqueous
is tat wad u trying to ask?

something close to that. eh, but isn't it that ONLY alkali metals (grp1) hydroxides are soluble? calcium is group 2. so are alkali are hydroxides?

wishboy SG

this is 'O' lvl ar?

bonkysleuth SG

this is 'O' lvl ar?

yea

wishboy SG

something close to that. eh, but isn't it that ONLY alkali metals (grp1) hydroxides are soluble? calcium is group 2. so are alkali are hydroxides?

ok...
A base is any metal oxide or hydroxide. (can be soluble or insoluble)
An alkali is a soluble base. (must be soluble)

Alkalis include KOH, NaOH, NH4OH, Ca(OH)2, Ba(OH)2, NH3 according to my tb. NH3 is a special case.

bonkysleuth SG

ok...
A base is any metal oxide or hydroxide. (can be soluble or insoluble)
An alkali is a soluble base. (must be soluble)

Alkalis include KOH, NaOH, NH4OH, Ca(OH)2, Ba(OH)2, NH3 according to my tb. NH3 is a special case.

one question. is calcium oxide soluble in water? it's a solid and a basic oxide. basic oxides are mostly insoluble. so if CaO is soluble, is it an exception of the basic oxides being insoluble statement?

wishboy SG

according to wiki

it reacts with water to from calcium hydroxide

CaO + H2O ---> Ca(OH)2

2nd qn i dunno

^tamago^ SG

partially soluble. forms lime water. yes, it is an exception. the other 2 soluble oxides here are potassium and sodium.

UltimaOnline SG

TS/OP asked about oxidation state of superoxide ion, eg. in KO2.
(+1) + 2(x) = 0
x = – 1/2
O.S. of superoxide ion is – 1/2.

UltimaOnline SG

(above post was truncated because I accidentally hit the ‘tab’ key and the cursor jumped to ‘save reply’ and auto-clicked before I finished typing).

To add to Tamago’s post about Ca(OH)2, as he said, it’s partially soluble. There are different names for when it is solid, and when it is aqueous.

Ca(OH)2 (aq) is called limewater.
Ca(OH)2 (s) is called slaked lime.