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3 years ago

A student neutralized 16.4 milliliters of HCl by adding 12.7 milliliters of 0.620 M KOH. What was the molarity of the HCl acid?

1 answer:

4 0

V ( HCl ) = 16.4 mL / 1000 => 0.0164 L

M( HCl) = ?

V( KOH) = 12.7 mL / 1000 => 0.0127 L

M(KOH) = 0.620 M

Number of moles KOH:

n = M x V

n = 0.620 x 0.0127

n = 0.007874 moles of KOH

number of moles HCl :

HCl + KOH = H2O + KCl

1 mole HCl ------ 1 mole KOH
? mole HCl--------0.007874 moles KOH

moles HCl = 0.007874 * 1 / 1

= 0.007874 moles of HCl

M = n / V

M = 0.007874 / 0.0164

= 0.480 M

Answer (2)

hope this helps!

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Step 1 : convert given masses into moles.

Moles of Ga = $\frac{\text{ given mass of Ga}}{\text{ molar mass of Ga}}= \frac{1.25g}{69.72g/mole}=0.0179moles$

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Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For Ga = $\frac{0.0179}{0.0179}=1$

For O = $\frac{0.027}{0.0179}=1.5$

The ratio of Ga : O = 1 : 1.5

To make in whole number we multiple ratio by 2, we get:

The ratio of Ga : O = 2 : 3

The mole ratio of the element is represented by subscripts in empirical formula.

The Empirical formula = $Ga_2O_3$

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Now we have to calculate the molecular formula of the compound.

Formula used :

$n=\frac{\text{Molecular formula}}{\text{Empirical formula weight}}$

$n=\frac{187.44}{187.44}=1$

Molecular formula = $(Ga_2O_3)_n=(Ga_2O_3)_1=Ga_2O_3$

Therefore, the chemical of the compound is, $Ga_2O_3$

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Calculating the theoretical mass deposited by using Faraday's law, which is:

$m=\frac{M\times I\times t(s)}{n\times F}$ ......(1)

where,

m = actual mass deposited = 1.25 g

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t = time period in seconds = 16.2 min = 972 s (Conversion factor: 1 min = 60 sec)

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F = Faraday's constant = 96500 C

Putting values in equation 1, we get:

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