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S_A_V [24]
3 years ago
5

The forensic technician at a crime scene has just prepared a luminol stock solution by adding 10.0 g of luminol into a total vol

ume of 75.0 mL of H2O . What is the molarity of the stock solution of luminol
Chemistry
1 answer:
Murrr4er [49]3 years ago
8 0

Answer:

0.753M

Explanation:

Molecular formula of luminol is as follows: C8H7N3O2

Molecular formula of the luminol (C8H7N3O2) = 12(8) + 1(7) + 14(3) + 16(2)

= 96 + 7 + 42 + 32

= 177g/mol

mole of luminol = mass/molar mass

mole = 10 ÷ 177

mole = 0.0565 mol

Molarity can be calculated using the formula: Molarity = mol/volume (L)

Volume of water = 75.0 mL = 75/1000

= 0.075L

Molarity (M) = 0.0565 ÷ 0.075

The molarity of the stock solution = 0.753M

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21-B. Mn was used as an internal standard for measuring Fe by atomic absorption. A standard mixture containing 2.00 mg Mn/mL and
Korvikt [17]

Answer:

0.0693M Fe

Explanation:

It is possible to quantify Fe in a sample using Mn as internal standard using response factor formula:

F = A(analyte)×C(std) / A(std)×C(analyte) <em>(1)</em>

Where A is area of analyte and std, and C is concentration.

Replacing with first values:

F = 1.05×2.00mg/mL / 1.00×2.50mg/mL

<em>F = 0.84</em>

In the unknown solution, concentration of Mn is:

13.5mg/mL × (1.00mL/6.00mL) = <em>2.25 mg Mn/mL</em>

Replacing in (1) with absorbances values and F value:

0.84 = 0.185×2.25mg/mL / 0.128×C(analyte)

C(analyte) = <em>3.87 mg Fe / mL</em>

As molarity is moles of solute (Fe) per liter of solution:

\frac{3.87 mg Fe}{mL} \frac{1g}{1000mg} \frac{1mol}{55.845g} \frac{1000mL}{1L} = <em>0.0693M Fe</em>

7 0
3 years ago
Read 2 more answers
Name the type of reaction involved in the conversation of ethanol to Ethan​
Anestetic [448]
The conversion of ethanol to ethanoic acid is an oxidation reaction.
3 0
2 years ago
What is a substance's melting point?
TEA [102]

A melting point of a substance is a point at which the sample or substance start converting in liquid. For most substances, melting and freezing points are approximately equal. For example, the melting point and freezing point of mercury is 234.32 kelvins (−38.83 °C or −37.89 °F). Hope this helped!! :)

5 0
2 years ago
Read 2 more answers
What is the nuclear charge of a berrylium atom?
ICE Princess25 [194]

Answer:

The charge on the nucleus of an atom; controlled by the number of protons and electrons present in an atom.

Explanation:

4 0
3 years ago
A eudiometer contains a 65.0 ml sample of a gas collected
SCORPION-xisa [38]

Answer:

53.1 mL

Explanation:

Let's assume an ideal gas, and at the Standard Temperature and Pressure are equal to 273 K and 101.325 kPa.

For the ideal gas law:

P1*V1/T1 = P2*V2/T2

Where P is the pressure, V is the volume, T is temperature, 1 is the initial state and 2 the final state.

At the eudiometer, there is a mixture between the gas and the water vapor, thus, the total pressure is the sum of the partial pressure of the components. The pressure of the gas is:

P1 = 92.5 - 2.8 = 89.7 kPa

T1 = 23°C + 273 = 296 K

89.7*65/296 = 101.325*V2/273

101.325V2 = 5377.45

V2 = 53.1 mL

6 0
3 years ago
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