Hi there!
The answer is no.
Although the real answer depends on what the pebble is composed of (since different materials produce different effects), most pebbles don't dissolve in water.
Hope this helps!
<u>Answer:</u> The number of atoms of bromine present in given number of mass is 
<u>Explanation:</u>
To calculate the number of moles, we use the equation:

Given mass of bromine = 1.37 g
Molar mass of bromine = 79.904 g/mol
Putting values in above equation, we get:

According to mole concept:
1 mole of an element contains
number of atoms.
So, 0.0171 moles of bromine will contain =
number of bromine atoms.
Hence, the number of atoms of bromine present in given number of mass is 
- Mass=m=750g=0.75kg
- Q=78.45\times 10^3J=78450J
- T_i=100°C
- T_f=?
- Specific heat capacity=c=4200J/kg°C
According to thermodynamics






Explanation:
divide the objects weight by the acceleration of gravity to find the mass
Https://www.google.com/search?q=how+to+solve+fir+atomic+mass+in+chemisty&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari#kpvalbx=1
Here is the link to a great video that explains your question nicely, hope this helps.