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Masteriza [31]
2 years ago
5

A quality control chemist at Dow Chemical tried to determine purity of NaOH using titration. He measured out 0.500 g NaOH sample

and dissolved it in 20 mL water. 22.5 mL of a 0.500 mol/L HCl solution was used to reach the end point. Assume the impurity did not react with HCl, what is the % purity of this NaOH sample?
Chemistry
1 answer:
Alex17521 [72]2 years ago
3 0

Answer:

89.94 %

Explanation:

Considering:

Molarity=\frac{Moles\ of\ solute}{Volume\ of\ the\ solution}

Or,

Moles =Molarity \times {Volume\ of\ the\ solution}

Given :

For HCl :

Molarity = 0.500 M

Volume = 22.5 mL

The conversion of mL to L is shown below:

1 mL = 10⁻³ L

Thus, volume = 22.5×10⁻³ L

Thus, moles of HCl :

Moles=0.500 \times {22.5\times 10^{-3}}\ moles

Moles of HCl = 0.01125 moles

The reaction of NaOH and HCl is:

NaOH + HCl ⇒ NaCl + H₂O

Moles of HCl = Moles of NaOH

<u>Thus, Moles of NaOH = 0.01125 moles</u>

Molar mass of NaOH = 39.997 g/mol

The formula for the calculation of moles is shown below:

moles = \frac{Mass\ taken}{Molar\ mass}

Thus,

0.01125\ moles= \frac{Mass}{39.997\ g/mol}

Mass of NaOH= 0.4497\ g

Total mass = 0.500 g

<u>% purity = ( 0.4497 / 0.500 ) × 100 = 89.94 %</u>

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The number in isotope platinum-194 stands for the <em>total </em>amount of protons and neutrons. In other words, this is the mass. =)
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Which of the samples described below contains the FEWEST atoms? No calculation is needed to answer this question.
Monica [59]

Hello!

To do this, use the molar mass. This is how much a mole of an atom weighs. A mole is 6.02214076×10²³ atoms.

Molar masses of:

Se: 78.96 g/mol

Cu: 63.546 g/mol

Ba: 137.327 g/mol

Now, the element with the highest molar mass will have the fewest atoms. This is because the element weighs more, so therefore for the same amount of mass, there will be less of the element needed to reach that mass.

Therefore, 10g of Ba would have the fewest number of atoms.

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6 0
2 years ago
Calculate the cell potential E at 25°C for the reaction 2 Al(s) + 3 Fe2+(aq) → 2 Al3+(aq) + 3 Fe(s) given that [Fe 2+] = 0.020 M
Elodia [21]

Answer:

1.18 V

Explanation:

The given cell is:

Al(s)/Al^{3+}(0.10M)||Fe^{2+}(0.020M)/Fe(s)

Half reactions for the given cell follows:

Oxidation half reaction: Al(s)\rightarrow Al^{3+}(0.10M)+2e^-;E^o_{Al^{3+}/Al}=-1.66V

Reduction half reaction: Fe^{2+}(0.020M)+2e^-\rightarrow Fe(s);E^o_{Fe^{2+}/Fe}=-0.45V

Multiply Oxidation half reaction by 2 and Reduction half reaction by 3

Net reaction: 2Al(s)+3Fe^{2+}(0.020M)\rightarrow 2Al^{3+}(0.10M)+3Fe(s)

Oxidation reaction occurs at anode and reduction reaction occurs at cathode.

To calculate the E^o_{cell} of the reaction, we use the equation:

E^o_{cell}=E^o_{cathode}-E^o_{anode}

Putting values in above equation, we get:

E^o_{cell}=-0.45-(-1.66)=1.21V

To calculate the EMF of the cell, we use the Nernst equation, which is:

E_{cell}=E^o_{cell}-\frac{0.059}{n}\log \frac{[Al^{3+}]^2}{[Fe^{2+}]^3}

where,

E_{cell} = electrode potential of the cell = ?V

E^o_{cell} = standard electrode potential of the cell = +1.21 V

n = number of electrons exchanged = 6

Putting values in above equation, we get:

E_{cell}=1.21-\frac{0.059}{6}\times \log(\frac{0.10^2}{0.020^3})\\\\E_{cell}=1.18V

5 0
2 years ago
Trichloromethane consists of 10.05% carbon. 0.83% hydrogen and 89.12% chlorine. if uts relative molecular mass is 119.5g . find
Delicious77 [7]

Answer:

C24H2CL213

Explanation:

C

(10.05/100)x119.5

=12x2=24

H

(0.083/100)x119.5

=1x2=2

Cl

(89.12/100)x119.5

=106.5x2=213

4 0
2 years ago
If different atoms can come together to form all living and nonliving things, why is there a limit to different combinations we
prohojiy [21]

Answer: gas dissolved in liquid

Explanation:

3 0
2 years ago
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