DETERMINATION OF MOLAR MASS PLEASE FILL IN HTE BLANKS. THANK YOU, PLEASE SHOW CA
ID: 910895 • Letter: D
Question
DETERMINATION OF MOLAR MASS
PLEASE FILL IN HTE BLANKS. THANK YOU, PLEASE SHOW CALCULATION.
what was used in the experiment: 25.00ml of standard HCL solution and 4 drops of phenolppthalien indicator and titrated with NaOH. cal teh equivalent weight of a basic oxide.
concentration of Standard HCL 0.302M
TRIAL 1 TRIAL 2 TRIAL 3 MASS PAPER AND SAMPLE 0.537G 0530G 0.541G MASS PAPER 0.115G 0.422G 0.428G FINAL BURET READING 38.50ML 39.50ML 37.30ML INITAL BURET READING 0 0 0 VOL OF NAOH USED ML ID STANDARD ACID ADDED MOL OF HCL ADDED MOL OF NAOH USED MOL OF HCL REACTED MOLAR MASS OF OXIDE AVG MOLAR MASS SUGGESTED FORMULA FOR OXIDEExplanation / Answer
[NB : You have not given the molarity of NaOH used for titration. Let it be x (M).]
The oxide is a basic oxide. A basic oxide is generally the oxide of alkali metals or alkaline earth metals.
The general reaction is: 2HCl + MaO = bMClc + H2O ...[ for oxide of alkali metals, a=b=2; c=1
for oxides of alkaline earth metals, a=b=1 ; c=2]
In both cases 2 moles of HCl is required to neutralise 1 mol of oxide. The excess HCl is back-titrated by NaOH.
For trial 1:
Mass of sample = 0.537-0.115 = 0.422 g
Volume of NaOH used = 38.5-0 = 38.5 mL
Volume of HCl added = 25 mL
Moles of HCl added = 0.302*25/1000 = 0.00755 mole
Moles of NaOH added = 38.5x/1000 ....[Put the value of x]
Moles of HCl reacted = [0.00755 - 38.5x/1000] = Z
[So, Z moles of HCl is reacted with oxide. No of moles of oxide in the sample = Z/2 moles
We get, Z/2 moles of oxide = 0.422 g
So, 1 mole oxide = 0.422*2/Z g]
Molar mass of oxide = 0.422*Z/2 g
[Now check the literature to match the molar mass of the oxide and detect it.
Do the same for other 2 trials.]
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