Answer:
1. Decomposition of stone due to acid rain.
3. The pink color of a rose.
Explanation:
Chemical changes always end up with new products in an equation, or it has always something to do with chemicals. Physical changes on the other hand, do not result in new products and it just changes the physical properties and physical state of matter of the object.
Answer:
Half life = 79.67 sec
Explanation:
Given that:
k = 
The expression for half life is shown below as:-
Where, k is rate constant
So,
Half life = 79.67 sec
Following reaction is involved in present system:
2KMnO4 + 5H2O2 + 3H2SO4 → 2MnSO4 + K2SO4 + 5O2 + 8H2O
From the above balance reaction, it can be seen that 2 moles of KMnO4 is consumed for every 5 moles of H2O2.
Now, percent by mass of hydrogen peroxide in the original solution can be estimated as follows:
percent by mass =

∴percent by mass =

= 4 %
C. soil. If this isn’t C it’s definitely B.