Question 6: Energy Use (8 points)

If the molar absorptivity constant for the red dye solution is 5.56×104 M-1cm-1, calculate the molarity of the red dye solution

Shtirlitz [24]

Explanation:

a) Using Beer-Lambert's law :

Formula used :

$A=\epsilon \times c\times l$

where,

A = absorbance of solution = 0.945

c = concentration of solution = ?

l = length of the cell = 1.20 cm

$\epsilon$ = molar absorptivity of this solution = $5.56\times 10^4 M^{-1} cm^{-1}$

$0.945=5.56\times 10^4 M^{-1} cm^{-1}\times 1.20 \times c$

$c=1.4163\times 10^{-5} M=14.16 \mu M$

( $1\mu M=10^{-6} M$ )

14.16 μM is the molarity of the red dye solution at the optimal wavelength 519nm and absorbance value 0.945.

b) $c=1.4163\times 10^{-5} mol/L$

1 L of solution contains $1.4163\times 10^{-5}$ moles of red dye.

Mass of $1.4163\times 10^{-5}$ moles of red dye:

$1.4163\times 10^{-5}\times 879.86g/mol=0.01246 g$

$(w/v)\%=\frac{\text{Mass of solute (g)}}{\text{Volume of solvent (mL)}}\times 100$

$red(w/v)\%=\frac{0.01246 g}{1000 mL}\times 100=0.001246\%$

c) In order to dilute red dye solution by 5 times, we will need to add 1 L of water to solution of given concentration.

Concentration of red dye solution = $c=1.4163\times 10^{-5} M$

Concentration of red solution after dilution = c'

$c=c'\times 5$

$1.4163\times 10^{-5} M=c'\times 5$

$c'=2.83\times 10^{-6} M$

The final concentration of the diluted solution is $2.83\times 10^{-6} M$

8 0

3 years ago

The salt formed by the reaction of the weak acid hydrocyanic acid, HCN, with the strong base potassium hydroxide is

iogann1982 [59]

Answer:

2.28 × 10^-3 mol/L

Explanation:

The equation for the equilibrium is

CN^- + H2O ⇌ HCN + OH^-

Ka = 4.9 × 10^-10

KaKb = Kw

4.9 × 10^-10 Kb = 1.00 × 10^-14

Kb = (1.00 × 10^-14)/(4.9 × 10^-10) = 2.05 × 10^-5

Now, we can set up an ICE table

CN^- + H2O ⇌ HCN + OH^-

I/(mol/L) 0.255 0 0

C/(mol/L) -x +x +x

E/(mol/L) 0.255 - x x x

Ka = x^2/(0.255 - x) = 2.05 × 10^-5

Check for negligibility

0.255/(2.05 × 10^-5) = 12 000 > 400. ∴ x ≪ 0.255

x^2 = 0.255(2.05 × 10^-5) = 5.20 × 10^-6

x = sqrt(5.20 × 10^-6) = 2.28 × 10^-3

[OH^-] = x mol/L = 2.28 × 10^-3 mol/L

5 0

3 years ago

Balance of Atoms Quick Check

san4es73 [151]

When iron rusts and forms iron oxide, the iron oxide has more mass than the iron because there are more iron atoms in iron oxide than in pure iron.

The process of rust occurs when pure iron is exposed to air and moisture. Rust is the oxidation of pure iron to iron II oxide (Fe2O3).

We can see that there are two iron atoms per mole of Fe2O3 whereas there is only one iron atom in each mole of pure iron.

Therefore, iron oxide has more mass than the iron because there are more iron atoms in iron oxide than in pure iron.

Learn more; brainly.com/question/18376414

3 0

3 years ago

Read 2 more answers

. The ring shape of the Cartwheel Galaxy is due to:

dlinn [17]

The ring shape of the Cartwheel Galaxy is due to collisions with another galaxy.

<h3>What causes the ring shape of the Cartwheel Galaxy?</h3>

The unusual shape of the Cartwheel Galaxy is due to a collision with a smaller galaxy. The recent star burst has lighted up the Cartwheel rim which has a diameter larger than that of the Milky Way galaxy in which our planet exists. The Cartwheel Galaxy is a lenticular ring galaxy which is about 500 million light-years away. This galaxy was discovered by Fritz Zwicky in the year 1941.

So we can conclude that the ring shape of the Cartwheel Galaxy is due to collisions with another galaxy.

Learn more about galaxy here: brainly.com/question/13956361

#SPJ1

7 0

1 year ago

Why is it the principle about the relationship between mass and volume always true of substance, but not always true of mixtures

Xelga [282]

Answer:

For pure substances, the mass and volume will always be the same or will always change the same way because all substance are the same throughout.

While for mixtures, you can have varying amount of each component therefore mass and volume will not change the same way for substances

7 0

1 year ago