MgBr2 is the chemical formula for magnesium bromide
X ml - <span>25% alcohol mixture
y ml - </span><span>90% alcohol mixture
x+y = 455
0.25x ml alcohol in </span>x ml of 25% alcohol mixture
0.9y ml alcohol in y ml of 90% alcohol mixture
0.75*455= 341.25 ml alcohol in 455 ml of 75% alcohol mixture
0.25x+0.9y=341.25
System of equations:
x+y = 455 /*(-0.25) ------> -0.25x-0.25y = -0.25*455
0.25x+0.9y=341.25
-0.25x-0.25y=-113.75
0.25x+0.9y=341.25 Add both equations
0.25x+0.9y-0.25x-0.25y=341.25-113.75
0.65y =227.5
y=227.5/0.65 = 350 ml of 90% alcohol mixture
x+y=455
x+355=455
x=100 ml of 25% alcohol mixture
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Answer:
KI
Explanation:
From the question, we can see that a qualitative analysis of the compound shows that it has a lilac flame colour. The lilac flame colour corresponds to the potassium ion (K^+).
Again, the test of addition of HNO3(aq) and AgNO3(aq) to a solution is a test for halogens. If the result is a green precipitate, then the ion present is the iodide ion (I^-).
Hence, the compound must be KI.
A reaction in which heat is evolved is an exothermic reaction while a reaction in which heat is absorbed is an endothermic reaction.
In the first case; Na2CO3 + H2SO4, we can see that this is an acid - base reaction therefore it is a neutralization reaction. Since the tube was hot after reaction, heat is given off so it is exothermic.
In the second case; NaOH + H2SO4, we can see that this is an acid - base reaction therefore it is a neutralization reaction. We are told that the tube is not hot but we don't know the initial temperature of the tube or if it was colder than it's initial temperature so we can not make any inference regarding whether the reaction is endothermic or exothermic.
Lastly, the reaction, NaCl + HC2H5OH does not occur so we mark "no reaction". We are told that the tube is not hot but we don't know the initial temperature of the tube or if it was colder than it's initial temperature so we can not make any inference regarding whether the reaction is endothermic or exothermic.
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