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2 years ago

A solid is 5 cm tall 3 cm wide and 2 cm thick it has a mass of 129 g what is the density

2 answers:

7 0

First you would multiply 5,3, and 2 to get a volume of 30. Density is mass over volume so you would then divide 129 by 30. You would get 4.3. The answer would be 4.3 g/cm^3

dlinn [17]2 years ago

4 0

<u>Answer:</u> The density of solid is $4.3g/cm^3$

<u>Explanation:</u>

To calculate the volume of cuboid, we use the equation:

$V=lbh$

where,

V = volume of cuboid

l = length of cuboid = 5 cm

b = breadth of cuboid = 3 cm

h = height of cuboid = 2 cm

Putting values in above equation, we get:

$V=5\times 3\times 2=30cm^3$

To calculate density of a substance, we use the equation:

$Density=\frac{Mass}{Volume}$

Putting values in above equation, we get:

$\text{Density of solid}=\frac{129g}{30cm^3}\\\\\text{Density of solid}=4.3g/cm^3$

Hence, the density of solid is $4.3g/cm^3$

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Which of the following statements is true about energy quantization at the atomic level? Electrons in the outermost orbits are t

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<h2>Answer:</h2>

The correct answer is option C which is, "Electrons in the orbit closest to the nucleus have the least amount of energy".

<h3>Explanation:</h3>

There are different orbitals around the nucleus on which the electrons moves around the nucleus.
These orbitals have a specific energy, due to which they are known as energy levels.
The energy level near to the nucleus has least amount of the energy and the energy of the orbitals increase as the distance of the orbitals increase to the nucleus.

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2 years ago

What is the pH of a 0.050 M triethylamine, (C2H5)3N, solution? Kb for triethylamine is 5.3 ´ 10-4. Question options: 1) 11.69 2)

blsea [12.9K]

<span>the pH of a 0.050 M triethylamine, is 11.70
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For triehtylamine, $(C_{2}H_{5})_{3}N$ , the reaction will be
$(C_{2}H_{5})_{3}N + H_{2}O ---\ \textgreater \ ( C_{2}H_{5})_{3}NH^{+} + OH^{-}$

and we know, pH = -log[H+] and pOH = -log[OH-]

Also, pOH + pH = 14

Now, the Kb value = 5.3 x 10^-4

And $kb = \frac{( [( C_{2}H_{5})_{3}NH^{+} ]* OH^{-} )}{[( C_{2}H_{5})_{3}N]}$

thus, [OH-] =(5.3 ^ 10-4) ^2 / 0.050

=0.00516 M

Thus, pOH = 2.30
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2 years ago

Which of the following describes the electron sharing between hydrogen and fluorine?

EastWind [94]

Hello
We know both the elements involved in bonding are non-metals and the primary type of bonds involved in non-metals are covalent bonds. Covalent bonds are formed when two atoms share one or more electrons; thus we know that whatever the number of electrons shared, it has to be equal for both. We can eliminate choices A and B.
Next, we understand that it is easier for one atom to be shared among the two, rather than the 7. First, because Hydrogen needs only 1 electron to be stable and would require energy to compensate the remaining 6. Second, electrons are attracted towards the nucleus so it is inefficient to try and share 7 electrons when 1 provides the same amount of stability to Fluorine.
Therefore, the answer is C.

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2 years ago

Read 3 more answers

A student dissolved a sample in hexane, spotted it on to a TLC plate and eluted using ethyl acetate. After visualizing the TLC p

Zepler [3.9K]

1) Consider the following silica gel TLC plate of compounds A, B, and C developed in hexanes:

<span><span>Determine the Rf values of compounds A, B, and C run on a silica gel TLC plate using hexanes as the solvent.</span>Which compound, A, B, or C, is the most polar?<span>What would you expect to happen to the Rf values if you used acetone instead of hexanes as the eluting solvent?</span><span>How would the Rf values change if eluted with hexanes using an alumina TLC plate?</span></span>

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2) You are trying to determine a TLC solvent system which will separate the compounds X, Y, and Z. You ran the compounds on a TLC plate using hexanes/ethyl acetate 95:5 as the eluting solvent and obtained the chromatogram below. How could you change the solvent system to give better separation of these three compounds?

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3) After a rather lengthy organic chemistry synthesis procedure, a student ran the product of the reaction on a TLC plate and obtained the result below. What might he/she have done wrong, if anything?

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4) A student spots an unknown sample on a TLC plate. After developing in hexanes/ethyl acetate 50:50, he/she saw a single spot with an Rf of 0.55. Does this indicate that the unknown material is a pure compound? What can be done to verify the purity of the sample?

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5) Consider a sample that is a mixture composed of biphenyl, benzoic acid, and benzyl alcohol. The sample is spotted on a TLC plate and developed in a hexanes/ethyl acetate solvent mixture. Predict the relative Rf values for the three compounds in the sample.

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6) Plate A, below, represents the TLC chromatogram of a compound run in hexanes. The same compound was then spotted on a large TLC plate and again run in hexanes. Which TLC plate, B, C, or D, correctly represents how far the compound would run on the longer plate?

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2 years ago

Dumbledore decides to gives a surprise demonstration. He starts with a hydrate of Na2CO3 which has a mass of 4.31 g before heati

vovikov84 [41]

Answer:

Na₂CO₃.2H₂O

Explanation:

For the hydrated compound, let us denote is by Na₂CO₃.xH₂O

The unknown is the value of x which is the amount of water of crystallisation.

Given values:

Starting mass of hydrate i.e Na₂CO₃.xH₂O = 4.31g

Mass after heating (Na₂CO₃) = 3.22g

Mass of the water of crystallisation = (4.31-3.22)g = 1.09g

To determine the integer x, we find the number of moles of the anhydrous Na₂CO₃ and that of the water of crystallisation:

Number of moles = $\frac{mass }{molar mass }$

Molar mass of Na₂CO₃ =[(23x2) + 12 + (16x3)] = 106gmol⁻¹

Molar mass of H₂O = [(1x2) + (16)] = 18gmol⁻¹

Number of moles of Na₂CO₃ = $\frac{3.22}{106}$ = 0.03mole

Number of moles of H₂O = $\frac{1.09}{18}$ = 0.06mole

From the obtained number of moles:

Na₂CO₃ H₂O

0.03 0.06

Simplest

Ratio 0.03/0.03 0.03/0.06

1 2

Therefore, x = 2

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2 years ago