Answer:
1st step : find the number of moles for the known substance
number of moles =mass/ relative molecular mass
n=23/Li2O2
n=23/(14+32)
n =23/46
n= 0,5moles
2nd step : balance the equation
2Li202 +2H20-----> 4LiOH +O2
3rd step : find the mole ratio of the known or stated using the balanced equation
Li2O2 : O2
2 : 1
4th step :find the number of moles for the asked using the mole ratio using simple proportion
Li2O2 :O2
2 :1
0,5 :???
0,5/2 ×1
= 0,25moles for (O2)
5th step : find the asked either mass , volume , concentration
number of moles = volume/molar gas volume
volume = number of moles × molar gas volume
v = 0,25moles × 28dm^3
v= 7 dm^3 of (O2)
The reactants that will form products will be 
.
<h3>Activity series</h3>
Elements at higher positions in the activity series will be able to displace those in lower positions in solutions.
Thus:
because Br is higher than I in the activity series.
Cl cannot displace F in 
because F is higher than Cl in the activity series.
Also, Cl is higher than Br in the activity series, thus, the reaction 
cannot form products.
I cannot displace F, thus, 
cannot form products.
More on activity series can be found here: brainly.com/question/13934381
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1,2-dimbromopropane would be something like C which is the second best answer.
B would be correct if it had another carbon.
A is like C but incorrect for the same reason. 1,2-dibromoethane is what A is.
The answer has to be D where the bromines are right across from each other.
Answer:
The number of protons also determines the identity of the element. ... Since the atom is electrically neutral, the number of electrons must equal the number of protons.
