Cr2O3+ 2Al -----------> 2Cr+ Al2O3
Cr2O3--------2Cr.
( oxidation no. of cr +3 to +1 means hain of electron so it act as oxidizing agent)
similarly,
2Al------> Al2O3
( oxidation no. of Al +1 to +3 means loss of electron so it act as reducing agent)
Answer:
It is a physical change.
Explanation:
While it is a chemical reaction because the salt gets dissolved, if you were to boil the water off of a salt solution, all that would be left is salt. This can be done physically. Thus, it is a physical change.
2NH₃(g) + CO₂(g) → CO(NH₂)₂(s) + H₂O(l)
is the balanced equation for the synthesis of urea.