Answer:
The expression to calculate the mass of the reactant is 
Explanation:
<em>The amount of heat released is equal to the amount of heat released per gram of reactant times the mass of the reactant.</em> To keep to coherence between units we need to transform 1,080 J to kJ. We do so with proportions:

Then,

Answer:Magnesium (Mg) is a - reactant
Hydrogen (H2) is a - product
magnesium chloride (MgCI2) is a - product
hydrochloric acid (HCI) is a - reactant
Explanation: It’s in my notes
17) 8.4 / 20 x 100
18) 20 . 0.5150
19) 6,50% because (as you said) the law of definite proportions states that regardless of the amount, a compound is always composed of the same elements in the same proportion by mass
Answer:
C) 8
Explanation:
Total number of carbon atoms = 3
Number of single bonds = 3
So, each carbon is bonded to the next carbon with the single bond, Number of unshared electrons left with the terminate carbons are 3 and with the intermediate carbon is 2.
Thus, the two terminate carbon have 3 hydrogen each and the intermediate will have 2.
<u>Total - 8</u>
I think the answer is -12.7