1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
ipn [44]
3 years ago
5

Keri has to identify a mysterious brown liquid in science class. She pours it through a filter, but the substance looks the same

. Then she heats the substance and collects the water that evaporates. The water droplets look the same as the original substance. Keri concludes that since the substance cannot be separated it must be a compound. Is Keri correct?
Chemistry
2 answers:
Rasek [7]3 years ago
6 0

Answer is: No, because the substance could be an element.

Pure substance is made of only one type of atom (element) or only one type of molecule, it has definite and constant composition with distinct chemical properties.

Pure substances can be separated chemically, not physically, that is difference between pure substances and mixtures.

Elements (for example copper, iron, sulfur) and compounds (water, sodium chloride) have definite and constant composition with distinct chemical properties.

Allisa [31]3 years ago
4 0

The answer is NO. It can not be a compound it is an element.

In a component mixture it can be separated physically way from the other.

In element it can be only separated by a way of destroying the compound itself by chemical reaction.

You might be interested in
What is the freezing point of an aqueous solution that has 25.00 g of calcium iodide dissolved in 1250 g of water?
ozzi

Answer:

<u></u>

  • <u>- 0.380ºC</u>

Explanation:

The lowering of the freezing point of a solvent is a colligative property ruled by the formula:

  • \Delta T_f=K_f\times m\times i

Where:

  • ΔTf is the lowering of the freezing point
  • Kf is the molal freezing constant of the solvent: 1.86 °C/m
  • m is the molality of the solution
  • i is the van't Hoff factor: the number of particles (ions) per unit of ionic compound.

<u />

<u>a) molality, m</u>

  • m = number of moles of solute/ kg of solvent
  • number of moles of CaI₂ = mass in grams/ molar mass
  • number of moles of CaI₂ = 25.00g / 293.887 g/mol = 0.0850667mol
  • m = 0.0850667mol/1.25 kg = 0.068053m

<u>b) i</u>

  • Each unit of CaI₂, ideally, dissociates into 1 Ca⁺ ion and 2 I⁻ ions. Thus, i = 1 + 2 = 3

<u />

<u>c) Freezing point lowering</u>

  • ΔTf =  1.86 °C/m × 0.068053m × 3 = 0.3797ºC ≈ 0.380ºC

<h2>I have problems to upload the full answer in here, so I attach a pdf file with the whole answer.</h2>
Download pdf
6 0
3 years ago
Photosynthesis uses 660-nm light to convert co2 and h2o into glucose and o2. calculate the frequency of this light.
Allushta [10]
The unit expressed in 660 nm of light represents the wavelength of light. If you want to determine the frequency, you use the speed of light to relate the two. The formula is:

c = λν
where
λ is the wavelength
ν is the frequency
c is the speed of light = 3×10⁸ m


Apply SI units:
(3×10⁸ m) = (660×10⁻⁹ m)(ν)
Solving for ν,
<em>ν = 4.55×10¹⁴ s⁻¹</em>
4 0
3 years ago
Caffeine (C8H10N4O2) is a weak base with a pKb of 10.4. Calculate the pH of a solution containing a caffeine concentration of 41
RSB [31]

Answer:

pH → 7.47

Explanation:

Caffeine is a sort of amine, which is a weak base. Then, this pH should be higher than 7.

Caffeine + H₂O  ⇄  Caffeine⁺  +  OH⁻      Kb

1 mol of caffeine in water can give hydroxides and protonated caffeine.

We convert the concentration from mg/L to M

415 mg = 0.415 g

0.415 g / 194.19 g/mol = 2.14×10⁻³ mol

[Caffeine] = 2.14×10⁻³  M

Let's calculate pH. As we don't have Kb, we can obtain it from pKb.

- log Kb = pKb → 10^-pKb = Kb

10⁻¹⁰'⁴ = 3.98×10⁻¹¹

We go to equilibrium:

Caffeine + H₂O  ⇄  Caffeine⁺  +  OH⁻      Kb

Initially we have 2.14×10⁻³ moles of caffeine, so, after the equilibrium we may have (2.14×10⁻³ - x)

X will be the amount of protonated caffeine and OH⁻

     Caffeine     +    H₂O  ⇄  Caffeine⁺  +  OH⁻      Kb

   (2.14×10⁻³ - x)                         x                x

We make the expression for Kb:

3.98×10⁻¹¹ = x² / (2.14×10⁻³ - x)

We can missed the -x in denominator, because Kb it's a very small value.

So: 3.98×10⁻¹¹ = x² / 2.14×10⁻³

√(3.98×10⁻¹¹ . 2.14×10⁻³) = x → 2.92×10⁻⁷

That's the [OH⁻].  - log [OH⁻] = pOH

- log 2.92×10⁻⁷ = 6.53 → pOH

14 - pOH = pH → 14 - 6.53 = 7.47

4 0
3 years ago
Look at the electron-dot diagram. What type of bond would two sulfur atoms require to form a molecule?
Blababa [14]

Answer:

Double Covalent

Explanation:

When two of the same element combine it will always be a covalent bond between them and since sulfur has two lone electrons it will make a double bond between the two to have a full octect

4 0
3 years ago
Any one know the answer?
quester [9]
The last one, answer is D
8 0
3 years ago
Other questions:
  • Which facts did you include in your response? Check all that apply.
    15·2 answers
  • What is a salt? A compound formed from a(n) from an acid and a(n) from a base.
    15·2 answers
  • Is it possible for an object not to be in motion and still have force acting upon it?
    15·1 answer
  • How does an atom with too many neutrons relative to protons undergo radioactive decay?
    13·2 answers
  • Lf the attractive forces among the solid are less than the attractive forces between the solid and a liquid, the solid will?
    8·1 answer
  • During an experiment, distilled water was placed in a sealed container and the container was heated gradually. Describe this sys
    11·1 answer
  • 17 OT-
    14·1 answer
  • Por qué razón se fomenta la inmigración Europea?​
    14·2 answers
  • What is a membrane?
    5·1 answer
  • Characteristic ions of water: OH- and H3O+​
    11·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!