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Step2247 [10]
3 years ago
8

Instead of using ratios for back titrations we can also use molarities, if our solutions are standardized. A 0.196 g sample of a

ntacid containing an unknown amount of triprotic base Al(OH)3 was reacted with 25.0mL of 0.111M HCl. The resulting solution was then titrated with 11.05mL of 0.132M NaOH solution. Calculate the mass percent of Al(OH)3 in the antacid sample.
Chemistry
1 answer:
kvv77 [185]3 years ago
3 0

Answer:

The mass percent of Al(OH)₃ is 15.3%

Explanation:

The reaction is:

Al(OH)₃ + 3HCl = AlCl₃ + 3H₂O

The excess acid is neutralized with a solution of sodium hidroxide, in the reaction:

NaOH + HCl = NaCl + H₂O

The total moles of HCl is:

n_{HCl,total} =M_{HCl} *V_{HCl} =0.111*0.025=2.78x10^{-3} moles

From the second titration, the moles of excess of HCl is:

n_{HCl,excess} =n_{NaOH} =M_{NaOH} *V_{NaOH} =0.132*0.01105=1.46x10^{-3} moles

The difference between the total and excess of HCl, it can be know the moles that reacts with the aluminum hydroxide, is:

n_{HCl,reacts} =n_{HCl,total}-n_{HCl,excess} =2.78x10^{-3} moles-1.46x10^{-3} moles=1.32x10^{-3} moles

The ratio between HCl and Al(OH)₃ is 3:1. The MW for aluminum hydroxide is 78 g/mol, thus:

m_{Al(OH)3} =1.32x10^{-3} molesHCl*\frac{1molAl(OH)3}{3molesHCl} *\frac{78gAl(OH)3}{1molAl(OH)3} =0.03g

The percentage of Al(OH)₃ is:

Percentage-Al(OH)3=\frac{m_{Al(OH)3} }{m_{antiacid} } *100=\frac{0.03}{0.196} =15.3%

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Menthol, which is present in mentholated cough drops, is an organic compound
Pie

Answer:

The empirical formula is C10H20O

Explanation:

Step 1: Data given

Mass of the sample = 0.2010 grams

Mass of CO2 = 0.5658 grams

Molar mass CO2 = 44.01 g/mol

Mass of H2O = 0.2318 grams

Molar mass H2O = 18.02 g/mol

Atomic mass C = 12.01 g/mol

Atomic mass O = 16.0 g/mol

Atomic mass H = 1.01 g/mol

Step 2: calculate moles CO2

Moles CO2 = 0.5658 gram / 44.01 g/mol

Moles CO2 = 0.01286 moles

Step 3: Calculate moles C

For 1 mol CO2 we have 1 mol C

For 0.01286 moles CO2 we have 0.01286 moles C

Step 4: Calculate mass C

MAss C = 0.01286 moles * 12.01 g/mol

Mass C =0.1544 grams

Step 5: Calculate moles H2O

Moles H2O =0.2318 grams / 18.02 g/mol

Moles H2O = 0.01286 moles

Step 6: Calculate moles H

For 1 mol H2O we have 2 moles H

For 0.01286 moles H2O we have 2*0.01286 = 0.02572 moles H

Step 7: Calculate mass H

Mass H = 0.02572 moles * 1.01 g/mol

Mass H = 0.0260 grams

Step8: Calculate mass O

Mass O = 0.2010 - 0.1544 - 0.0260

Mass O = 0.0206 grams

Step 9: Calculate moles O

Moles O = 0.0206 grams / 16.0 g/mol

Moles O = 0.00129 moles

Step 10: Calculate the mol ratio

We divide by the smallest amount of moles

C: 0.01286 moles / 0.00129 moles =  10

H: 0.02572 moles / 0.00129 moles = 20

O: 0.00129 moles / 0.00129 moles = 1

The empirical formula is C10H20O

4 0
3 years ago
Read 2 more answers
if the theoretical yield of a reaction is 26.0 grams and you actually recovered 22.0 grams what is the precent yield
netineya [11]
Percentage Yield = (Actual Yield ÷ Theoretical Yield) × 100  

∴ if theoretical yield is 26 g, but only 22.0 is recovered from the reaction, 
then Percentage Yield = (22 g ÷ 26 g) × 100  
                                       =  84.6 %
8 0
3 years ago
What is a controlled factor in an experiment?
Romashka-Z-Leto [24]
Sorry this will probably be pretty long.

So think of the "control" as being something you yourself add to increase or decrease the effects in an experiment.
I'll give you an example so it is not as confusing.
Say you have decided to make an experiment on plants. Which plant can grow the fastest on which type of liquid? What is being added to this experiment? The liquid! Or all of the liquids you used. Like if you used Coke, Lime Gatorade, Orange Gatorade, and Water. Each drink will EFFECT each plant differently.
Hope I was of any hope?
3 0
3 years ago
Suppose a student started with 142.0 mg of trans-cinnamic acid, 412 mg of pyridinium tribromide, and 2.30 mL of glacial acetic a
nirvana33 [79]

Answer: Theoretical Yield = 0.2952 g

               Percentage Yield = 75.3%

Explanation:

Calculation of limiting reactant:

n-trans-cinnamic acid moles = (142mg/1000) / 148.16 = 9.584*10⁻⁴ mol

pyridium tribromide moles = (412mg/1000) / 319.82= 1.288*10⁻³ mol

  • n-trans-cinnamic acid is the limiting reactant

The molar ratio according to the equation mentioned is equals to 1:1

The brominated product moles is also = 9.584*10⁻⁴ mol

Theoretical yield = (9.584*10⁻⁴ mol) * (Mr of brominated product)

                             =  (9.584*10⁻⁴ mol) * (307.97) = 0.2952 g

Percentage Yield is : Actual Yield / Theoretical Yield = 0.2223/0.2952

                                                                                           = 75.3%

4 0
3 years ago
Which of the following are strong electrolytes? Hcl hc2h3o2 nh3 kcl
Arturiano [62]
<h3><u>Answer;</u></h3>

HCl and KCl

<h3><u>Explanation</u>;</h3>
  • Strong electrolytes are strong bases and acids.
  • HCl is a strong acid; it dissociates completely to form H+ and Cl- ions. Thus, it is a strong, rather than weak, electrolyte.
  • CH3COOH is acetic acid, a weak acid. Only some of it will dissociate (to H+ and acetate ions), thus, it will only be a weak electrolyte.
  • NH3 will react with water as a weak base: NH3 + H2O → NH4+ + OH-. It will thus also be a weak electrolyte.  
  • KCl is a soluble ionic compound, and as such, it will be a strong electrolyte.
5 0
3 years ago
Read 2 more answers
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