When a mineral was heated strongly to constant mass, a colourless gas that formed a white precipitate with limewater was evolved. The remaining solid was cooled and added to dilute hydrchloric acid. Vigorous efferverscence was seen. What was the mineral?
A. aragonite, CaCO3
B. artinite, MgCO3.Mg(OH)2.3H2O
C.dolomite, MgCO3.CaCO3
D.gaylussite, Na2CO3.CaCO3.5H2O
the formulas way confusing so I have no idea how to start with this question!
2006-10-30 18:36:17 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
can you tell me why?
2006-10-30 18:50:38 · update #1
The answer is Gaylussite. D.
The question is like a puzzle you just need to take it step by step.
1. The fact that the mineral can be heated to constant mass (it loses mass as heated) suggests that it has water molecules attached to it which can be vaporized. This lets us narrow down the answer to B and D, hydrated minerals.
2. When the water is evaporated, the process called calcination occurs with calcium carbonate. When Carbonate ores are heated in absence of air, the absence of air and heat converts the metal carbonate into CO2 gas and metal oxide.
The fact that CO2(g) forms is confirmed by the gas reacting with limewater, Ca(OH)2(aq) to from white ppt, which is CaCO3(s).
3. Now, what are left of the Gaylussite are only Na2O and CaCO3. And it makes sense to see that with addition of HCl, vigorous eff forms because as you know, CaCO3 + HCl --> H2CO3 + CaCl2. Carbonic Acid (H2CO3) from this rxn immediately breaks down into CO2 gas and water to which appears as vigorous effervescence that can be easily seen.
·Answers A, B, and C are not your choice because after calcinations, they would not have metal carbonate left to form eff with HCl after it is cooled. Sodium Carbonate however, won’t calcinate as easily as alkaline earth metal carbonates such as Mg(CO3)2 or Ca(CO3)2.
Thus your logical choice is D.
2006-10-30 20:17:14 · answer #1 · answered by †ђ!ηK †αηK² 6 · 0⤊ 0⤋
The right answer is D. Evolution of gas after the mineral was added to dilute hydrochloric acid suggests that there were still some carbonate ions that did not decompose during the heating. A, B and C yield only oxides (A - CaO, B - MgO, C - MgO + CaO), while D decomposes to Na2CO3 + CaO, since Na2CO3 won't decompose even when heated to 1000 deg. C. The effervescence comes from the reaction between Na2CO3 and hydrochloric acid (CO2 is formed).
2006-10-30 20:01:11 · answer #2 · answered by tweenk_pl 1 · 0⤊ 0⤋
Non carbonated. Women can suffer from osteoarthritis later in life if the drink too many carbonated drinks;
2016-05-22 14:44:06 · answer #3 · answered by Anonymous · 0⤊ 0⤋
D In brief, step 1 Na2CO3.CaCO3.5H2O →Na2CO3+CaO+CO2↑+5H2O ↑
step 2 Na2CO3+2HCl→2NaCl+CO2↑+H2O
sorry,response so late.
2006-10-30 18:44:57 · answer #4 · answered by fritz 1 · 0⤊ 0⤋