S3 Chem (20點)
1) Being very light, helium can be used to fill balloons and airships. Predict whether xenon can also be used. Explain your answer.
2)Name the products formed for each of the following chemical changes
-->Magnesium is burnt in air
-->Calcium is put into water
3)Describe what would be observed when a piece of strontium is put into dilute
4) Give 2 pieces of evidence that strontium is more reactive than magnesium.
- 7 年前最愛解答
1. It cannot be used to fill balloons and airships because the molar mass of He is 4.0 and the molar mass of air is about 15. By Avogadro's law, the volume of all gas is same if the amount of molecules are equal,therefore the density oftwo gases can be compared, regardless of the volume. As the mass of He is smaller than air, balloons and airships can float on air when they are filled with He. However, the molar mass of Xe is131.3 which is much larger than He and air. It cannot float on air.
Mg will react with the O2 in air when it is burnt ,with the equation
Ca will react with H2O when it is put into water, with the equation
3. It will give a large amount of colourless gas bubbles due to these reactions
4.Sr can react water in room temperature and pressure but Mg cannot.
Sr has a higher position in ECS than Mg which shows that it loses electrons more easily than Mg資料來源： me
- 7 年前
1. Xenon is less light than helium but i'm not sure whether it can make them float
2.Magnesium is burnt in air--> Magnesium oxide
Calcium is put into water--> Calcium hydroxide
3. colourless bubbles give out
4. It gives out more bubbles when put into dilute acid (hydrogen)
The reaction between strontium with water has a higher rate than that of magnesium with water
- 匿名7 年前
u can find the answer in the hk a-level pastpaper (topic:inorganic chem)