Chem paper 1 ques + others

[Saturation]

CAn someone pls explain to mw how to do qsuestion 11?

http://www.xtremepapers.net/CIE/Cambridge IGCSE/0620 - Chemistry/0620_w07_qp_1.pdf

I dont unerstand it! :? :? :?

And if Aluminium is placed in an acid, will it react? I m guessing no, because of the protective oxide coating on the surface? If so, how come metals such as magnesium react with acid? Why dont their oxides coating protect them?

And finally, is Calcium hydroxide soluble?. Can someone please tell me which metal oxides and hyroxides are solubale, cause i'm really confused with solubility

Thanks a million, and good luck!

 

[PN94]

About question 11, it was kinda confusing at first, but then u've got to read more than once ... anyhow it tells u tht ONE molecule of organic compound need EIGHT molecules of O2 to form complete combustion... so basically its got to do with balancing, so unfortunately u've got to try each one, nd try to balance the equation so tht ... in the end u would have only 1 mol of the compound nd 8 of the O2 but the CO2 nd H2O can vary ... srry if its not clear how i explained ... but try nd see if it works out

 

[LoayTYS]

CAn someone pls explain to mw how to do qsuestion 11?

http://www.xtremepapers.net/CIE/Cambridge IGCSE/0620 - Chemistry/0620_w07_qp_1.pdf

I dont unerstand it! :? :? :?

And if Aluminium is placed in an acid, will it react? I m guessing no, because of the protective oxide coating on the surface? If so, how come metals such as magnesium react with acid? Why dont their oxides coating protect them?

And finally, is Calcium hydroxide soluble?. Can someone please tell me which metal oxides and hyroxides are solubale, cause i'm really confused with solubility

Thanks a million, and good luck!

Q1) You need to try and balance each and every equation in the 4 answers (Fuel+Oxygen----->Carbon dioxide+Water)
Q2)Aluminium will react with acid because the oxide layer can be removed and when we right equations we assume so
Magnesium is less reactive because once you remove the oxide layers and compare its reactivity with Aluminium you will find Aluminium more reactive which justifies the position of Aluminium in the reactivity series.
Q3)All hydroxides are insoluble except Sodium,Potassium,Ammonium and Calcium thus Calcium hydroxide is soluble

I hope I have clarified all your doubts

 

[Saturation]

Thanks for both of ur replies! but when you add NaOH to a calcium containing compound, a white precipitate of calcium hydroxide is formed. So doesn't that mean it's insoluble?

 

[LoayTYS]

Thanks for both of ur replies! but when you add NaOH to a calcium containing compound, a white precipitate of calcium hydroxide is formed. So doesn't that mean it's insoluble?

Yes but you also have to consider the fact that Calcium hydroxide can exist as aqeous solution dissolved in water moreover Calcium hydroxide is lime water which is a liquid and not a precipitate.

Hope it is clearer now