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Oksana_A [137]
4 years ago
13

A student standardizes a solution of aqueous NaOH against a measured mass of solid potassium hydrogen phthalate. She then uses t

his NaOH solution to titrate a measured mass of an unknown monocarboxylic acid to its phenolphthalein endpoint to determine its molar mass.
1. Which errors will lead to a value of the molar mass that is too high?
I. The potassium hydrogen phthalate is partially hydrated.
II. The NaOH solution is allowed to stand after being standardized and absorbs some carbon dioxide from the air.
(A) I only
(B) II only
(C) Both I and II
(D) Neither I nor II
Chemistry
1 answer:
wlad13 [49]4 years ago
8 0

Answer:

(D) Neither I nor II

Explanation:

The reagent potassium hydrogen phthalate is found in pure form and it is not partially hydrated .

The pallet form of NaOH ( solid form )  absorbs carbon dioxide gas from the atmosphere but NaOH in solution form does not absorb carbon dioxide .

Hence option D ) is right choice .

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What are the components of black powder? What are the ratios of these components?
NeTakaya
 75:15:10.  componets inlcude <span>mixture of </span>sulfur<span>, charcoal, and </span>potassium nitrate<span> (</span>saltpeter<span>)</span>
6 0
4 years ago
Lithium has two stable isotopes with masses of 6.01512 amu and 7.01600 amu. The average molar mass of Li is 6.941 amu. What is t
Dvinal [7]

Answer :  The percent abundance of Li isotope-1 and Li isotope-2 is, 6.94 % and 93.1 % respectively.

Explanation :

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i   .....(1)

Let the fractional abundance of Li isotope-1 be 'x' and the fractional abundance of Li isotope-2 will be '100-x'

For Li isotope-1 :

Mass of Li isotope-1 = 6.01512 amu

Fractional abundance of Li isotope-1 = x

For Li isotope-2 :

Mass of Li isotope-2 = 7.01600 amu

Fractional abundance of Li isotope-2 = 100-x

Average atomic mass of Li = 6.941 amu

Putting values in equation 1, we get:

6.941=[(6.01512\times x)+(7.01600\times (100-x))]

By solving the term 'x', we get:

x=694.048

Percent abundance of Li isotope-1 = \frac{694.048}{100}=6.94\%

Percent abundance of Li isotope-2 = 100 - x = 100-6.94 = 93.1 %

6 0
3 years ago
For the reaction of reducing benzil (MW 210.23 g/mol) with sodium borohydride (MW 37.83 g/mol), if 2.56 g of benzil and 0.38 g o
disa [49]

Answer:

NaBH₄

Explanation:

First, we need to write the chemical formula of all the compounds:

Benzil: C₁₄H₁₀O₂

Sodium Borhydride: C₁₄H₁₀O₂

Hydrobenzoin: C₁₄H₁₄O₂

Now, let's write the reaction that is taking place and write all the products:

C₁₄H₁₀O₂ + 2NaBH₄ + 2H₂O -----------> C₁₄H₁₄O₂ + 2BH₃ + 2NaOH

We can see that the reaction is already balanced, so we don't need to do anything else.

The question of this exercise is to determine the limiting reagent of the reaction, in other words, the reagent that controls the reaction and produces the 2.22 g of the hydrobenzoin. And to know this we need to see the mole ratio in both reactants, and compare them to the given moles (That can be obtained with the given masses and MW)

According to the above reaction, we have a mole ratio of 1:2, so, let's calculate the moles of benzil and the borohydride, and see which of them is the limiting reactant:

moles C₁₄H₁₀O₂ = 2.56 / 210.23 = 0.0122 moles

moles NaBH₄ = 0.38 / 37.83 = 0.01 moles

moles  C₁₄H₁₄O₂ = 2.22 / 214.26 = 0.0103 moles

We have the moles of every species, now, let's see the mole ratio

If 1 mole of C₁₄H₁₀O₂ -----------> 2 moles of NaBH₄

Then 0.0122 moles C₁₄H₁₀O₂ ----------> X moles of NaBH₄

Solving for X:

X = 0.0122 * 2 / 1 = 0.0244 moles of NaBH₄ are required.

However, we only have 0.01 moles of NaBH₄, and we need so much more of this to completely react with the moles of the benzil. Therefore we can safely assume that the limiting reagent is the NaBH₄

Another data that we can use for this, is the fact the produced moles were 0.0103, and this value is nearest to the moles of NaBH₄ rather than the moles of the benzil.

<h2>So, in conclusion, Limiting reagent NaBH₄</h2>

Hope this helps

7 0
3 years ago
Copper is formed when aluminum reacts with copper (II) sulfate in a single-replacement reaction. How many moles of copper can be
serg [7]

Answer:

The answer to your question is the limiting reactant is CuSO₄ and 0.975 moles of Cu were obtained

Explanation:

moles of Copper = ?

mass of Aluminum = 29 g

mass of CuSO₄ = 156 g

Limiting reactant = ?

Balanced Chemical reaction

                  3 CuSO₄   +  2 Al   ⇒   3 Cu   +  Al₂(SO₄)₃

Calculate the moles of reactants

CuSO₄ = 64 + 32 + (16 x 4) = 160g

Al = 27 g

                160 g of CuSO₄  ----------------- 1 mol

                156 g                   -----------------  x

                      x = (156 x 1) / 160

                      x = 0.975 moles

               27 g of Al -------------------------- 1 mol

               29 g of Al -------------------------- x

                x = (29 x 1)/27

                x = 1.07 moles

Calculate proportions to find the limiting reactant

Theoretical     3 moles CuSO₄/2 moles Al = 1.5 moles

Experimental  0.975 moles CuSO₄/1.07 moles = 0.91

The experimental proportion was lower than the theoretical proportion that means that the limiting reactant is CuSO₄.      

                    3 moles of CuSO₄ ------------------ 3 moles of Cu

                 0.975 moles of CuSO₄ ---------------  x

                         x = (0.975 x 3)/3

                        x = 0.975 moles of Cu were obtained.        

3 0
3 years ago
Read 2 more answers
Who wants to hang out?
vovangra [49]
What’s the question?
7 0
3 years ago
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