Hey there!
1.)
The law of conservation of mass states that matter cannot be created or destroyed. This means in a chemical reaction, the products must be equal to the reactants.
2.)
In a balanced chemical equation, there are the same amount of each type of atom, or element, on each side. The products must be equal to the reactants to follow the law of conservation of mass.
3.)
When a chemical reaction occurs, we can see evidence such as bubbles, odor, color change, and heat/light being released. These all are signs that a new substance is being formed.
Hope this helps!
Group 17 is the most readily reduced elements on the periodic table, meaning that they are so close to being a stable elements, only missing 1 electron to complete their valance electron shell. Thus they will essentially react with anything to get that last electron!
Group 1 elements are extremely reactive because they are the most readily oxidized, they are very close to reaching stability by giving up only 1 electron. Thus they will react with almost anything to give up their electron.
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The enthalpy change is negative.
The other statements are false because:
Can take place without a catalyst
Energy is given out to the surroundings.
Kinetic energy of products is higher.