You can find chemistry in daily life in the foods you eat , the air you breathe , and cleaning chemicals . For example , chemistry holds the explanation for why ice floats , while most substances sink when they freeze .
Answer:
exothermic reaction
Explanation:
The definition of exothermic is:
describing a process that involves the release of energy into the surroundings by substances undergoing change.
Think of<em> ex</em>-othermic as energy exiting/ released and <em>en</em>-dothermic as energy entering.
Explanation:
The given data is:
The mass% of a solution is 7.
Mass of solution =450g
The mass of salt required can be calculated as shown below:

Substitute the given values in this formula to get the mass of solute that is salt:

Mass of salt =31.5g
Mass of solvent that is water = 450g-31.5g=418.5g
#2 reactivity is the answer
Answer:
H3PO4 + 5 HCl → PCl5 + 4 H2O
Explanation:
The given equation is
H3PO4 + HCl = PCl5 + H2O
The above chemical equation has one P atom on both the sides, hence phosphorus is balanced
There are 5 Cl on the RHS but only one Cl on the LHS. On balancing the chlorine, we get -
H3PO4 + 5HCl = PCl5 + H2O
Now, there are 8 hydrogen atom on the LHS but only two on the RHS. On balancing the hydrogen on both the sides, the new equation become
H3PO4 + 5HCl = PCl5 + 4H2O
Let us check for oxygen
Oxygen on LHS = 4 and oxygen on RHS = 4
Thus, the balanced equation is H3PO4 + 5HCl = PCl5 + 4H2O