A white sold V is heated strongly. at high temperature, v gives off CO2 and changes to a solid W that begins to glow.
when water is added to W, it begins to fizz, produces heat and crumbles to powder X
X dissolves in water to form an alkaline solution Y.
When carbon dioxide is passed into solution Y, solution turns cloudy. the cloudiness is caused by a white suspension Z and its formation is used as a test for carbon dioxide.
Deduce the identities of unknown alphabets.
Not sure whether mine are correct. But here goes:
v - MgCO3
W - MgO
x - unsure
y - Mg(OH)2
z - calcium carbonate? (please explain)
Will go examine the question again. meanwhile, please do help.
Happy New Year!
Originally posted by anpanman:A white sold V is heated strongly. at high temperature, v gives off CO2 and changes to a solid W that begins to glow.
when water is added to W, it begins to fizz, produces heat and crumbles to powder X
X dissolves in water to form an alkaline solution Y.
When carbon dioxide is passed into solution Y, solution turns cloudy. the cloudiness is caused by a white suspension Z and its formation is used as a test for carbon dioxide.
Deduce the identities of unknown alphabets.
Not sure whether mine are correct. But here goes:
v - MgCO3
W - MgO
x - unsure
y - Mg(OH)2
z - calcium carbonate? (please explain)
Will go examine the question again. meanwhile, please do help.
Happy New Year!
V - CaCO3 (s)
W - CaO (s)
X - Ca(OH)2 (s)
Y - Ca(OH)2 (aq)
Z - CaCO3 (s)
What exactly is your question? Which part do you have doubts or queries?
For instance, why did you choose magnesium? As you yourself said, from the last sentence of the question, they're referring to calcium, so why did you choose magnesium?
And adding water to hot metal oxides produces their hydroxides, which may be in solid or aqueous form, depending on its solubility (eg. Grp I vs Grp II) and on whether water is limiting or in excess (water is needed for two reasons - to combine with oxide to form hydroxide, then later to act as a solvent).
Any further questions?
Originally posted by UltimaOnline:
V - CaCO3 (s)W - CaO (s)
X - Ca(OH)2 (s)
Y - Ca(OH)2 (aq)
Z - CaCO3 (s)
What exactly is your question? Which part do you have doubts or queries?
For instance, why did you choose magnesium? As you yourself said, from the last sentence of the question, they're referring to calcium, so why did you choose magnesium?
And adding water to hot metal oxides produces their hydroxides, which may be in solid or aqueous form, depending on its solubility (eg. Grp I vs Grp II) and on whether water is limiting or in excess (water is needed for two reasons - to combine with oxide to form hydroxide, then later to act as a solvent).
Any further questions?
The question says that a solid W is formed, that glows. As far as I know, a reaction between magnesium and steam produces magnesium oxide and hydrogen. And in this reaction a "glow" is seen. Since magnesium is about the only substance I know that glows in a reaction, I chose that as the answer. I didn't know CaO glows! Haha. Anyway, may I know how you can identify the right choices smartly when you meet such ambiguous questions?
Lots of thanks
Originally posted by anpanman:The question says that a solid W is formed, that glows. As far as I know, a reaction between magnesium and steam produces magnesium oxide and hydrogen. And in this reaction a "glow" is seen. Since magnesium is about the only substance I know that glows in a reaction, I chose that as the answer. I didn't know CaO glows! Haha. Anyway, may I know how you can identify the right choices smartly when you meet such ambiguous questions?
Lots of thanks
Any substance, when hot enough, glows (some of the heat energy is transformed into light energy). And the question states "at high temperature".
If you feel the question is ambiguous, you'll have to state all possible answers, conditionally. See the 1st post of my thread here (http://www.sgforums.com/forums/2297/topics/320107).
As for questions in which you have unknown compounds A, B, C, X, Y, Z, etc, and are asked to identify them, you'll have to use elimination.
Based on the info given in the question, start thinking of all possible compounds that could be A, B, C etc, and as you consider the rest of the info, start eliminating the possibilities until you end up with the most likely answer.
For instance, you were right that it could be mangesium (carbonate, oxide, hydroxide, etc), but the last sentence of the question reveals it to be calcium. So you eliminate magnesium (or barium, or whatever other metal it could possibly have been, from the earlier info in the question).
Qualitative Analysis (Q.A.) is a fun topic, and the questions are like puzzles for you to solve. Of course, in order to have fun with them, you must first be familiar with your "identification of cations, anions and gases".
Organic Chemistry (O.C.) can also have similar questions, of unknown compounds X, Y, Z, etc.
For instance, one fun question I give my students :
Compound A liberates carbon dioxide gas with calcium carbonate, but produces only a small percentage of carbon dioxde gas (when reacted with calcium carbonate) as compared with hydrochloric acid (of the same molarity as an aqueous solution of A). Compound B decolourizes acidified potassium manganate(VII). Both compounds A and B have a molar mass of 74g each, and both compounds contain only 3 elements. When an equimolar mixture of A and B is boiled (together with a few drops of sulfuric acid as catalyst), an equilibrium mixture is obtained, which contains a new compound C, which is sweet smelling.
Draw compounds A, B and C.
Originally posted by UltimaOnline:
Any substance, when hot enough, glows (some of the heat energy is transformed into light energy). And the question states "at high temperature".
If you feel the question is ambiguous, you'll have to state all possible answers, conditionally. See the 1st post of my thread here (http://www.sgforums.com/forums/2297/topics/320107).
As for questions in which you have unknown compounds A, B, C, X, Y, Z, etc, and are asked to identify them, you'll have to use elimination.
Based on the info given in the question, start thinking of all possible compounds that could be A, B, C etc, and as you consider the rest of the info, start eliminating the possibilities until you end up with the most likely answer.
For instance, you were right that it could be mangesium (carbonate, oxide, hydroxide, etc), but the last sentence of the question reveals it to be calcium. So you eliminate magnesium (or barium, or whatever other metal it could possibly have been, from the earlier info in the question).
Qualitative Analysis (Q.A.) is a fun topic, and the questions are like puzzles for you to solve. Of course, in order to have fun with them, you must first be familiar with your "identification of cations, anions and gases".
Organic Chemistry (O.C.) can also have similar questions, of unknown compounds X, Y, Z, etc.
For instance, one fun question I give my students :
Compound A liberates carbon dioxide gas with calcium carbonate, but produces only a small percentage of carbon dioxde gas (when reacted with calcium carbonate) as compared with hydrochloric acid (of the same molarity as an aqueous solution of A). Compound B decolourizes acidified potassium manganate(VII). Both compounds A and B have a molar mass of 74g each, and both compounds contain only 3 elements. When an equimolar mixture of A and B is boiled (together with a few drops of sulfuric acid as catalyst), an equilibrium mixture is obtained, which contains a new compound C, which is sweet smelling.
Draw compounds A, B and C.
Ok thanks. WIll try to solve the question ASAP when i am free.