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Usimov [2.4K]
3 years ago
15

Suppose you will determine the composition of the unknown substance that was collected at the scene of the crime. You are encour

aged to work on this case. You can perform a series of tests on the unknown substance and compare results of the same tests performed on known samples. Follow these steps:
List physical properties you can use as a simple method of identifying substances.

Describe how you can use density to help identify unknown substances.

Explain how forensic chemist can help you identify unknown substances.

How important is comparing tests results of know substances in a lab setting?
Chemistry
1 answer:
maria [59]3 years ago
6 0

Answer:

b   erergart

Explanation:

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Help i have no idea what i’m doing and i’m failing this class
m_a_m_a [10]

Answer:

c

Explanation:

esuba is activation energy

8 0
3 years ago
When 42.5 g of benzamide (C7H7NO) are dissolved in 500 g of a certain mystery liquid X, the freezing point of the solution is 6.
LuckyWell [14K]

Answer:

21.3g of Fe(NO₃)₃ are required to produce the same depression in freezing point of solution.

Explanation:

Freezing point depression is a colligative property which indicates, in determined mixture, the freezing point of solution is lower that the freezing point of the solvent, according the amount of solute.

Formula is: ΔT = Kf . m . i

Kf is the cryoscopic constant, which is particular for each solvent. We do not have that data, so we need to find it out in order to solve the question:

ΔT = Freezing point of pure solvent - Freezing point of solution.

This data is known → 6.40°C

m, means molality, moles of solute in 1kg of solvent. Let's get the moles of benzamide: 42.5 g . 1mol / 121g = 0.351 moles

m = 0.351 mol / 0.5kg = 0.702 m

As benzamide is an organic compound i, = 1. i are the number of ions dissolved in solution. Let's find out Kf:

6.40°C = Kf . 0.702 m . 1

6.40°C /0.702m = 9.11 °C/m.

Let's go to the next question.

ΔT is the same → 6.40°C

But this is, an inorganic salt, a ionic salt: Fe(NO₃)₃ →  1Fe³⁺  + 3NO₃⁻

For this case, we have 1 mol of Iron(III) and 3 nitrates, so i = 4

Let's replace data: 6.40°C = 9.11 °C/m . m . 4

6.40°C / (9.11 m/°C . 4) = 0.176 m

This data represents that, in 1 kg of solvent we have 0.176 moles of nitrate.

Mass of solvent X required in this case is 0.500 kg, so, the moles that are contained are: 0.500 kg . 0.176 mol/kg = 0.088 mol

Let's determine the mass of salt: 0.088 mol . 241.85g /1mol = 21.3 g

5 0
3 years ago
when metals react they ________________ (gain/lose) electrons. as you go down any group containing metals, it becomes easier to
balandron [24]

Answer:

When metals react they lose electrons.

Explanation:

An ion is defined as a molecule or atom made up of a different number of electrons and protons. This makes the electric charge of the molecule net, not neutral.

In other words, an ion is a molecule or atom that has a positive or negative electric charge, making it an atom whose electric charge is not neutral.

The characteristic property of a metallic atom is to lose one or more of its electrons to form a positive ion. That is, metals lose electrons and acquire a net positive charge, which is why they are electropositive.

4 0
3 years ago
Butane<br> methane<br> ethane<br> propane
aleksklad [387]
<h3>Further explanation</h3>

Given

the structure of the alkanes

Required

match the image to the name

Solution

Alkanes are saturated hydrocarbons with all of the carbon bonds being single bonds

General formula:

\large {\boxed {\bold {C_nH_2n + 2}}}

If we look at the picture, we define the black atom as Carbon and the branch is Hydrogen

To determine the name of the alkane, all we have to do is count the number of Carbon atoms

Butane : C₄H₁₀ : 4 C atoms

Methane : CH₄ : 1 C atom

Ethane : C₂H₆ : 2 C atoms

Propane : C₃H₈ : 3 C atoms

7 0
3 years ago
What are the effects of convection currents in our surroundings?
miskamm [114]
Land breeze sea breeze,ventilation,etc
8 0
4 years ago
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