Energy is conserved in chemical reactions. It is neither created nor
An exothermic reaction
transfers energy
the reacting substances
the surroundings. An
reaction transfers energy from the surroundings to the reacting substances

destroyed, from, endothermic

Explanation:

Energy is conserved in chemical reactions. It is neither created nor destroyed but can be transferred from one form to another.

An exothermic reaction transfers energy from the reacting substance to the surroundings. The body of the container feels warm. An exothermic reaction has a negative value of enthalpy.

An endothermic reaction transfers energy from the surroundings to the reacting substance. The body of the container feels cold. In an endothermic reaction, enthalpy is positive.

1. 1 mole of anything contains 6.022x10^23 pieces  

d  

2. a  

3. c, number  

5. 1.24x10^24atoms / 6.022x10^23atoms/mole = 2moles h2 atoms  

6. fe2br3 mass = 2moles x mass fe + 3 moles x mass br  

molar mass = grams / number of moles = g/mole  

to find moles = g / molar mass  

to find mass = g = molar mass / moles

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