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sesenic [268]
3 years ago
7

A scientific theory _______.

Chemistry
2 answers:
Aliun [14]3 years ago
8 0

CORRECT ANSWER IS D!! I TOOK THE TEST

A scientific theory _______.

a.

describes what occurs every time in a given situation

b.

is not validated by experimentation

c.

can never be changed

<u>d. </u>

<u>is an explanation for a set of events</u>

Butoxors [25]3 years ago
3 0

describes what occurs every time in a given situation


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An animal cell loses the ability to convert energy stored in food to energy that the cell can use. Which of the cell's organelle
olga55 [171]
The correct answer is A. Mitochondria is the one that is responsible for everything that has to do with energy.
5 0
3 years ago
How many milliliters of 0.200 m fecl3 are needed to react with an excess of na2s to produce 1.38 g of fe2s3 if the percent yield
ahrayia [7]
<span>Answer: 100 ml
</span>

<span>Explanation:


1) Convert 1.38 g of Fe₂S₃ into number of moles, n


</span>i) Formula: n = mass in grass / molar mass
<span>
ii) molar mass of </span><span>Fe₂S₃ =2 x 55.8 g/mol + 3 x 32.1 g/mol = 207.9 g/mol
</span>

iii) n = 1.38 g / 207.9 g/mol = 0.00664 moles of <span>Fe₂S₃
</span>

<span>2) Use the percent yield to calculate the theoretical amount:
</span>

<span>65% = 0.65 = actual yield/ theoretical yield =>


</span>theoretical yield = actual yield / 0.65 = 0.00664 moles / 0.65 = 0.010 mol <span>Fe₂S₃</span><span>

3) Chemical equation:
</span>

<span> 3 Na₂S(aq) + 2 FeCl₃(aq) → Fe₂S₃(s) + 6 NaCl(aq)


4) Stoichiometrical mole ratios:
</span>

<span>3 mol Na₂S : 2 mol FeCl₃ : 1 mol Fe₂S₃ : 6 mol NaCl


5) Proportionality:


</span>2moles FeCl₃ / 1 mol Fe₂S₃ = x / 0.010 mol Fe₂S₃
<span>
=> x = 0.020 mol FeCl₃


6) convert 0.020 mol to volume
</span>

<span>i) Molarity formula: M = n / V
</span>

<span>ii) V = n / M = 0.020 mol / 0.2 M = 0.1 liter = 100 ml
</span>

3 0
3 years ago
Read 2 more answers
Compare the polymerisation reaction used to produce poly(ethene) with the
butalik [34]

Answer:

See explanation

Explanation:

Polymerization is the process whereby two or more monomers link together to form a compound of high molecular mass called a polymer.

There are two kinds of polymers;

-Addition polymers

-Condensation polymers

Addition polymers are formed by the joining of two or more monomers  to form a polymer without the elimination of a small molecule.

Condensation polymers are formed by the joining of two or more molecules  to form polymers with the elimination of a small molecule.

The main difference between polyethene and polyester is that polyethene is an addition polymer while polyester is a condensation polymer.

In polyethene, ethene molecules are joined together having the repeating unit as [-CH2-CH2-]n.

In polyester, the polymer arises from the reaction of carboxylic acid and an alcohol and loss of water molecules.

5 0
3 years ago
Identify the group number of following oxides/hydrides in Mendeleev
Ivan

Answer:

See explanation

Explanation:

The oxides or hydrides are formed by exchange of valency between the two atoms involved. The group of the atom bonded to oxygen or hydrogen in the binary compound can be deduced by considering the subscript attached to the oxygen or hydrogen atom.

Now let us take the journey;

R2O3- refers to an oxide of a group 13 element, eg Al2O3

R2O - refers to an oxide of group a group 1 element e.gNa2O

RO2 - refers to an oxide of a group 14, 15 or 16 element such as CO2, NO2 or SO2

RH2 - refers to the hydride of a group 12 element Eg CaH2

R2O7 - refers to an oxide of a group 17 element E.g Cl2O7

RH3- refers to a hydride of a group 13 element E.g AlH3

5 0
3 years ago
If 24.6 grams of lithium react with excess water, how many liters of hydrogen gas can be produced at 301 Kelvin and 1.01 atmosph
andreev551 [17]
Answer: 43.3 l


Explanation:

1) Chemical equation:
2 Li(s) + 2 H₂O (l) → 2LiOH(aq) + H₂ (g)

2) Mole ratios:

2 mol Li : 2 mol H₂O : 2 mol LiOH : 1 mol H₂

3) Number of moles of Li that react

n = mass in grams / atomic mass = 24.6g / 6.941 g/mol = 3.54 moles

4) Yield

Proportion:

2 mol Li / 1 mol H₂ = 3.54 mol  Li/ x


⇒ x = 3.54 mol Li × 1 mol H / 2 mol Li = 1.77 mol H₂

4) Ideal gas equation

PV = nRT ⇒ V = nRT / P

V = 1.77 mol × 0.0821 [atm×l / (mol×K)] × 301 K / 1.01 atm = 43.3 l


V = 43.3 l ← answer



7 0
3 years ago
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