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3 years ago

How do you analyze chemical evidence?

1 answer:

3 0

BIOLOGICAL & CHEMICAL EVIDENCE ANALYSIS
There are many different types of evidence that can be found at a crime scene. Physical evidence can be collected at the crime scene such as a murder weapon. Chemical evidence is any residue from liquids that such as poison and drugs. Biological evidence is when hair or skin from a persons body has been transferred to a physical surface and then be collected and tested.

This evidence can be used to find out what exactly happened at the scene of the crime, the history behind the crime and who was involved and could have committed it.

Our experts test and analyse many forms of evidence, which is vital when finding out the various incidences that happened at a crime scene.

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The conversation of cyclopropane to propene in the gas phase is a first order reaction with a rate constant of 6.7x10-⁴s-¹. a) i

Rus_ich [418]

Answer: a) The concentration after 8.8min is 0.17 M

b) Time taken for the concentration of cyclopropane to decrease from 0.25M to 0.15M is 687 seconds.

Explanation:

Expression for rate law for first order kinetics is given by:

$t=\frac{2.303}{k}\log\frac{a}{a-x}$

where,

k = rate constant

t = age of sample

a = let initial amount of the reactant

a - x = amount left after decay process

a) concentration after 8.8 min:

$8.8\times 60s=\frac{2.303}{6.7\times 10^{-4}s^{-1}}\log\frac{0.25}{a-x}$

$\log\frac{0.25}{a-x}=0.15$

$\frac{0.25}{a-x}=1.41$

$(a-x)=0.17M$

b) for concentration to decrease from 0.25M to 0.15M

$t=\frac{2.303}{6.7\times 10^{-4}s^{-1}}\log\frac{0.25}{0.15}\\\\t=\frac{2.303}{6.7\times 10^{-4}s^{-1}}\times 0.20$

$t=687s$

7 0

3 years ago

In the following reaction, which substance is the precipitate? (NH4)2SO4(aq) + Ba(NO3)2(aq) BaSO4(s) + 2NH4NO3(aq

mariarad [96]

Assuming that the reactants are:

(NH4)2SO4 (aq) + Ba(NO3)2 (aq)

and the products are:

BaSO4 (s) + 2NH4NO3 (aq),

then you will have to determine which product is insoluble. You should have access to solubility rules to help you determine this.

According to the solubility rules, the following elements are considered insoluble when paired with SO4:

Sr^2+, Ba^2+, Pb^2+, Ag^2+, and Ca^2+

Therefore, the precipitate will be BaSO4 (s).

5 0

3 years ago

Read 2 more answers

When water freezes into ice, sme of the properties have changed <br> What stays the same

larisa86 [58]

When water freezes into ice, some of the properties have change. What stays the same.

Answer: 1: Ice Melting is a physical change. When liquid water (H2O) freezes into a solid state (ice), it appears changed; However, this change is only physical as the the composition of the constituent molecules is the same: 11.19% hydrogen and 88.81% oxygen by mass.

Have a goood day!

5 0

2 years ago

Particles that are smaller and have ____ generally dissolve faster.(1 point)

saw5 [17]

Answer:

For many solids dissolved in liquid water, the solubility increases with temperature. The increase in kinetic energy that comes with higher temperatures allows the solvent molecules to more effectively break apart the solute molecules that are held together by intermolecular attractions.

Explanation:

7 0

3 years ago

Read 2 more answers

What mass of nitrous oxide gas (N2O) is contained in 20.0 L balloon at a pressure of 110.0 kPa and a temperature of 25 C?

likoan [24]

Answer:

40.94 g

Explanation:

Given data:

Mass of NO₂ = ?

Volume = 20.0 L

Pressure = 110.0 Pka

Temperature = 25°C

Solution:

Pressure = 110.0 KPa (110/101 = 1.1 atm)

Temperature = 25°C (25+273 = 298.15 K)

The given problem will be solve by using general gas equation,

PV = nRT

P= Pressure

V = volume

n = number of moles

R = general gas constant = 0.0821 atm.L/ mol.K

T = temperature in kelvin

n = PV/RT

n = 1.1 atm × 20.0 L / 0.0821 atm.L/ mol.K ×298.15 K

n = 22 / 24.5 /mol

n= 0.89 mol

Mass of NO₂:

Mass = number of moles × molar mass

Mass = 0.89 mol × 46 g/mol

Mass = 40.94 g

3 0

3 years ago