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2 years ago

What is the molar mass of a compound if 25.0 g of the compound dissolved in 750. Ml gives a molarity of 0.290 m?

Chemistry

1 answer:

wlad13 [49]2 years ago

6 0

Answer:

115g/mol

Explanation:

To get the molar mass, we know that the it is equal to the mass divided by the number of moles. We have the mass but we do not have the number of moles.

We get this by working through the solution information. Firstly, we need to know the number of moles in 750ml for a molarity of 0.29m

Now, since 0.29 moles is present in 1000ml, x moles will be present in 750ml

The value of x is obtained as follows:

x = (750 * 0.29)/1000 = 0.2175 moles

Now since we have the number of moles, we can then obtain the molar mass.

Molar mass = mass/number of moles = 25.0g/0.2175 = 114.94 approximately 105g/mol

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A molecular biologist measures the mass of Cofactor A in an average yeast cell. The mass is 77.91pg. What is the total mass in m

Anni [7]

In this question, you are given the average cofactor mass per cell (77.91pg) and the total cells count(10^5 cells). You are asked how much cofactor that will be found from those cells(microgram= 10^6 picogram). Then the calculation would be:
Cofactor mass= cofactor per cell * cell count= 77.91pg/cell * 10^5 cells= 7.791 x 10^6pg

Then convert the picogram(pg) into microgram: 7.791x 10^6pg/ (10^6pg/microgram)= 7.791 microgram

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2 years ago

ANSWER FOR: How did the lab activities help you answer the lesson question "How do the processes of conduction, convection, and

Alenkinab [10]

<u>Answer</u>: Conduction, convection, and radiation move energy from the Sun to Earth and throughout Earth.

Without more information about the experiment itself, I would choose the above answer as correct. All the other statements are correct, however none of them relates to the earth distribution processes on Earth. The last statement does.

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2 years ago

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Why are the concentrations of [H3O+] and [OH−] equal in pure water?

kotegsom [21]

Answer : The correct option is, (A) $[H_3O^+]=[OH^-]$ because one of each is produced every time an $[H^+]$ transfers from one water molecule to another.

Explanation :

As we know that, when the two water molecule combine to produced hydronium ion and hydroxide ion.

The balanced reaction will be:

$HOH+HOH\rightarrow H_3O^++OH^-$

Acid : It is a substance that donates hydrogen ion when dissolved in water.

Base : It is a substance that accepts hydrogen ion when dissolved in water.

From this we conclude that, the hydrogen ion are transferred from one water molecule to the another water molecule to form hydronium ion and hydroxide ion. In this reaction, one water molecule will act as a base and another water molecule will act as an acid.

Hence, the correct option is, (A)

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2 years ago

Describe how you would prepare exactly 100 mL of 0.109 M picolinate buffer, pH 5.61. Possible starting materials are pure picoli

Pepsi [2]

Answer:

1.342g of picolinic acid and 6.743mL of 1.0M NaOH diluting the mixture to 100.0mL

Explanation:

<em>The pKa of the picolinic acid is 5.4.</em>

Using Henderson-Hasselbalch formula for picolinic-picolinate buffer:

pH = pKa + log [Picolinate] / [Picolinic]

<em>Where [] could be taken as moles of each species</em>

<em />

5.61 = 5.4 + log [Picolinate] / [Picolinic]

0.21 = log [Picolinate] / [Picolinic]

1.62181 = [Picolinate] / [Picolinic] <em>(1)</em>

Now, both picolinate and picolinic acid will be:

0.100L * (0.109mol / L) =

0.0109 moles = [Picolinate] + [Picolinic] <em>(2)</em>

First, as we will start with picolinic acid, we need add:

0.0109 moles picolinic acid * (123.10g/mol) = 1.342g of picolinic acid

Now, replacing (2) in (1):

1.62181 = 0.0109 moles - [Picolinic] / [Picolinic]

1.62181 [Picolinic] = 0.0109 moles - [Picolinic]

2.62181 [Picolinic] = 0.0109 moles

[Picolinic] = 4.157x10⁻³ moles

And:

[Picolinate] = 0.0109 - 4.157x10⁻³ moles =

<h3>6.743x10⁻³ moles</h3><h3 />

To obtain these moles of picolinate ion we need to make the reaction of the picolinic acid with NaOH:

Picolinic acid + NaOH → Picolinate + Water

<em>That means to obtain 6.743x10⁻³ moles of picolinate ion we need to add 6.743x10⁻³ moles of NaOH</em>

<em />

6.743x10⁻³ moles of NaOH that is 1.0M are, in mL:

6.743x10⁻³ moles * (1L / 1mol) = 6.743x10⁻³L * 1000 =

<h3>6.743mL of the 1.0M NaOH must be added</h3><h3 />

Thus, we obtain the desire moles of picolinate and picolinic acid to obtain the buffer we want, the last step is:

<h3>Dilute the mixture to 100mL, the volume we need to prepare</h3>

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2 years ago

Oxalic acid is a diprotic acid. calculate the percent of oxalic acid (h2c2o4) in a solid given that a 0.7984-g sample of that so

vlada-n [284]

This method of quantitative determination of percent purity is titrimetric reactions. These reactions most commonly involve neutralization reactions between an acid and a base. Then, we look at the neutralization reaction:

H₂C₂O₄ + 2 NaOH ⇒ Na₂C₂O₄ + 2 H₂O

So, we do the stoichiometric calculations. The important data we should know is the molar mass of oxalic acid which is equal to 90 g/mol.

(0.2283 mol/L NaOH * 0.3798 L * 1 mol H₂C₂O₄/ 2mol NaOH * 90 g/mol H₂C₂O₄) ÷ 0.7984 g *100%
= 488%

This is impossible. The purity can't be more than 100%. Looking at our calculations and the balance reaction, all steps were done correctly. So, I think there is some typographical error in the given. The mass of the sample should be 7.984 g. Then, the answer would be 48.87% purity.

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2 years ago

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