A. Covalent bonds is the answer
<span>Balancing is making sure there are the same number of atoms on either side of the reaction.
Pb(NO3)2 + Li2SO4--> PbSO4 + LiNO3
There are 2 NO3 groups and 2 Li on the right side, need 2 on the left side.
Need a coefficient of 2 for LiNO3
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The standard enthalpy of reaction should be negative.
<h3>What is enthalpy?</h3>
A thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.
Inside the heat pack are two chemicals that get mixed when you smush them together. As they mix, some weak bonds are broken, which takes a little bit of energy. But new, stronger bonds form which release energy. Releasing that energy causes the surroundings to heat up.
Hence, option B is correct.
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Answer:

Explanation:
= First mass of water = 12 oz
= Second mass of water = 20 oz
= Temperature difference of the solution with respect to the first mass of water =
= Temperature difference of the solution with respect to the second mass of water = 
c = Specific heat of water
As heat gain and loss in the system is equal we have

The final temperature of the solution is
.
Answer:
an atom is the smallest particle of matter
a compound is a substance that has two or more atoms and element is the opposite of compound.
molecule is........,...............hope this helps