combine science (chemistry)

如何讀好化學? 多做練習?

是！做的愈多，見的便愈多，記得的東西便愈多，成績便愈好。

1. Rubidium (Rb) is a Group I element below potassium in the periodic table.
Which of the following statements about rubidium are correct?

(1) Its oxide is a crystalline solid.
(2) Metallic bonding exists in it.
(3) The chemical formula of its sulphate is Rb2SO4.

A (1) and (2) only
B (1) and (3) only
C (2) and (3) only
D (1), (2) and (3) <------ why (D) is the answer?

Na₂O 和 K₂O 都是固體 ( 室温 )，可以估計 Rb₂O 都是固體。


melting point of Rb
http://en.wikipedia.org/wiki/Rubidium_oxide
2. Strontium (Sr) is a Group II element below calcium in the periodic table.
Which of the following statements about strontium are correct?

(1) Its chemical formula is SrCO3.
(2) It conducts electricity in solid state.
(3) It is insoluble in water.

A (1) and (2) only
B (1) and (3) only <------ why (B) is the answer?
C (2) and (3) only
D (1), (2) and (3)

答案錯！ Sr 是導電的！


Sr conducts electricity
http://wiki.answers.com/Q/Does_strontium_chloride_conduct_electricity#slide=23. Which of the following substances is the most stable in moist air?
3. Which of the following substances is the most stable in moist air?

A Ca
B Na
C SiO2 <------ why (C) is the answer?
D SO2

SiO₂ 是我們脚下的沙沙石石，它當然不會和水有反應啦！

4. Consider the following substances:
Carbon dioxide (CO2), silicon dioxide (SiO2) and sodium oxide (Na2O)

The ascending order of the melting points of these substances is

A CO2 < Na2O < SiO2 <------ why (A) is the answer?
B CO2 < SiO2 < Na2O
C SiO2< CO2 < Na2O
D Na2O< SiO2< CO2

CO₂在室溫已經是氣體，熔點當然很低，SiO₂是沙石，火山爆發，大約 3000 度才熔。

2014-02-08 18:02:56 補充：
melting point of sodium oxide

1132 °C

http://en.wikipedia.org/wiki/Sodium_oxide

melting point of SiO₂

1,600 to 1,725 °C

http://en.wikipedia.org/wiki/Silicon_dioxide