All categories

4 years ago

Which of the following is the most sensitive and reliable procedure for extracting combustible residues?

Chemistry

2 answers:

Norma-Jean [14]4 years ago

4 0

Answer

B. gas chromatography

Explanation:

NARA [144]4 years ago

3 0

Answer:

gas chromatography

Explanation:

You might be interested in

Write a sentence or mathematical expression that relates each of the

11111nata11111 [884]

Answer:

Mass to moles: mass/molar mass=mole

Moles to mass: moles x molar mass = mass

Moles to particles:1mole = 6.022x10^23 particles

Particles to moles: 1 particle =1/(6.022x10^23) mole

Explanation:

8 0

3 years ago

A weak base is titrated with a hydrochloric acid solution. What is the pH at the equivalence point?A) equal to pKaB) equal to 7C

zvonat [6]

Answer:

E) less than 7

Explanation:

pH is defined as the negative logarithm of the concentration of hydrogen ions.

Thus,

pH = - log [H⁺]

pH scale generally runs from 1 to 14 where pH = 7 represents neutral medium, pH < 7 represents acidic medium and pH > 7 represents basic medium.

Strong acids dissociate completely and when they react with base they form a salt of weak base and strong acid.

For example, $BOH$ is a weak base and $HCl$ is the hydrochloric acid.

So,

$BOH+HCl\rightarrow BCl+H_2O$

<u>Thus, the salt is of weak base and strong acid which corresponds to pH less than 7.</u>

4 0

4 years ago

At this pressure, how many molecules of air would there be in a 20 ∘C experimental chamber with a volume of 0.020 m3 ?

jonny [76]

Answer:

Explanation: The lowest pressure in a laboratory is 4.0×10^-11Pa

Using Ideal gas equation

PV = nRT

P= 4.0×10^-11Pa

V= 0.020m^3

T= 20+273= 293k

n=number of moles = m/A

Where m is the number of molecules and A is the Avogradro's number=6.02×10²³/mol

R=8.314J/(mol × K)

PV= m/A(RT)

4.0×10^-11 ×0.020 = m/6.02×10²³(8.314×293)

m = 4.0×10^-11×0.020×6.02×10^23 / (8.314×293)

m = 1.98×10^8 molecules

Therefore,the number of molecules is 1.98×10^8

8 0

3 years ago

How many electrons, protons and neutrons are in the element tin

lisabon 2012 [21]

Answer: Tin has 48 electrons, 69 neutrons, and 50 protons.

Explanation:

4 0

3 years ago

Experiment #1A melting point of an old sample of Naphthalene was completed and a melting range of 77-83 oC was observed and reco

White raven [17]

Answer:

%error = 0.32%

Explanation:

Let's answer both questions, by parts.

1. Percentage error:

In this case, I do not have the video, but I do have the reported melting point of naphtalene which is 80.26 °C.

The expression to calculate the percentage error is the following:

%Error = absolute error / actual percentage. (1)

And the absolute error is:

Abs error = actual value - experimental value (2)

But the experimental value is a range, so we just have to get a average of that:

Exp value = 77 + 83 / 2 = 80 °C

Now the absolute error:

Abs error = 80.26 - 80 = 0.26 °C

Finally the %error:

%error = (0.26 / 80.26) * 100

<h2>%error = 0.32%</h2>

2. Meaning of melting point range and %error

The melting point range just means that the sample of naphtalene has impurities, and when a sample of any compound has impurities, melting point tends to be low. However, this decrease of temperature is a wider range. But usually a range of just 5° C means that compound has little traces of impurities but it can still be used for reactions.

The %error means that the impurities of the sample are really low, so the sample is practically pure with little traces of impurities.

3 0

3 years ago