Sure, let's break down the given problem step-by-step to determine the correct description of the metal ribbon 'X', the ash 'Y', and the type of reaction involved.
When the metal ribbon 'X' burns in oxygen with a dazzling white flame, it forms a white ash 'Y'. We need to identify 'X', 'Y', and the type of reaction it represents.
1. Option (a):
- [tex]\( X = \text{Ca} \)[/tex]
- [tex]\( Y = \text{CaO} \)[/tex]
- Type of reaction = Decomposition
A decomposition reaction is when a compound breaks down into its constituent parts. However, in this context, we are discussing a metal burning in oxygen, which suggests that a metal ribbon is reacting with oxygen, not decomposing.
2. Option (b):
- [tex]\( X = \text{Mg} \)[/tex]
- [tex]\( Y = \text{MgO} \)[/tex]
- Type of reaction = Combination
Magnesium (Mg) burns with a dazzling white flame when it reacts with oxygen, forming magnesium oxide (MgO), a white ash. This is a combination reaction, where magnesium and oxygen combine to form a single product, magnesium oxide.
3. Option (c):
- [tex]\( X = \text{Al} \)[/tex]
- [tex]\( Y = \text{Al}_2\text{O}_3 \)[/tex]
- Type of reaction = Thermal decomposition
Thermal decomposition involves the breakdown of substances through the application of heat. However, when aluminum burns in oxygen, it forms aluminum oxide ([tex]\( \text{Al}_2\text{O}_3 \)[/tex]), which is not a decomposition reaction but rather a combination reaction. So, the type of reaction stated here is incorrect in this context.
4. Option (d):
- [tex]\( X = \text{Zn} \)[/tex]
- [tex]\( Y = \text{ZnO} \)[/tex]
- Type of reaction = Endothermic
While zinc can react with oxygen to form zinc oxide (ZnO), this reaction typically does not produce a dazzling white flame, and it is not classified as an endothermic reaction. An endothermic reaction absorbs heat, but burning zinc in oxygen usually releases energy.
After evaluating all the options, we identify that Option (b) describes the correct scenario:
- Magnesium (Mg) burns with a dazzling white flame.
- It forms magnesium oxide (MgO), a white ash.
- The type of reaction is a combination reaction.
Thus, the correct description is:
[tex]\( \boxed{X = \text{Mg}; Y = \text{MgO}; \text{Type of reaction} = \text{Combination}} \)[/tex]
Hence, the correct answer is (b).
