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3 years ago

If you know the number of moles in a sample of a substance, which of the following do you also know about that sample?

Chemistry

2 answers:

jekas [21]3 years ago

8 0

Answer:

You also know about the mass of that sample, if you know the moles

(First option)

Explanation:

Moles = Mass / Molar mass

Moles . Molar mass = Mass

For example, I have 4 moles of H₂O

Molar mass H₂O = 18 g/m

4 m . 18 g/m = 72 g

If I have 4 moles of H₂O, I also have 72 grams of water too.

Lelu [443]3 years ago

8 0

Answer:

The correct answer is the number of representative particles in that sample

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(6) Compare a CSTR with a PFR below. a. A flow of 0.3 m3/s enters a CSTR (volume of 200 m3) with an initial concentration of spe

Dmitry [639]

Answer:

Explanation:

Given that:

The flow rate Q = 0.3 m³/s

Volume (V) = 200 m³

Initial concentration $C_o$ = 2.00 ms/l

reaction rate K = 5.09 hr⁻¹

Recall that:

$time (t) = \dfrac{V}{Q}$

$time (t) = \dfrac{200}{0.3}$

$time (t) = 666.66 \ sec$

$time (t) = \dfrac{666.66 }{3600} hrs$

$time (t) = 0.185 hrs$

$\text{Using First Order Reaction:}$

$\dfrac{dc}{dt}=kc$

where;

$t = \dfrac{1}{k} \Big( \dfrac{C_o}{C_e}-1 \Big)$

$0.185 = \dfrac{1}{5.09} \Big ( \dfrac{200}{C_e}- 1 \Big)$

$0.942 = \Big ( \dfrac{200}{C_e}- 1 \Big)$

$1+ 0.942 = \Big ( \dfrac{200}{C_e} \Big)$

$\dfrac{200}{C_e} = 1.942$

$C_e = \dfrac{200}{1.942}$

$\mathbf{C_e = 102.98 \ mg/l}$

Thus; the concentration of species in the reactant = 102.98 mg/l

b). If the plug flow reactor has the same efficiency as CSTR, Then:

$t _{PFR} = \dfrac{1}{k} \Big [ In ( \dfrac{C_o}{C_e}) \Big ]$

$\dfrac{V_{PFR}}{Q_{PFR}} = \dfrac{1}{k} \Big [ In ( \dfrac{C_o}{C_e}) \Big ]$

$\dfrac{V_{PFR}}{Q_{PFR}} = \dfrac{1}{5.09} \Big [ In ( \dfrac{200}{102.96}) \Big ]$

$\dfrac{V_{PFR}}{Q_{PFR}} =0.196 \Big [ In ( 1.942) \Big ]$

$\dfrac{V_{PFR}}{Q_{PFR}} =0.196(0.663)$

$\dfrac{V_{PFR}}{0.3 hrs} =0.196(0.663)$

$\dfrac{V_{PFR}}{0.3*3600 sec} =0.196(0.663)$

$V_{PFR} =0.196(0.663)*0.3*3600$

$V_{PFR} = 140.34 \ m^3$

The volume of the PFR is ≅ 140 m³

3 0

3 years ago

How many moles of NaF are produced in the resction between sodium bromide and calcium fluoride when 550 grams of sodium bromide

bija089 [108]

Answer: 5 moles of NaF would be produced when 550 grams of Sodium bromide are used.

Explanation:

From the question, the balanced chemical formula is illustrated below:

2NaBr + CaF2 → 2NaF + CaBr2

From the equation above;

Molecular mass of NaBr = 23 + 80 = 103g/ mol

Molecular mass of CaF2= 40+ (19×2)= 78g/ mol

Molecular mass of NaF = 23+19 = 42g/ mol

From the balanced chemical equation;

2 moles of NaBr reacted with 1mole of CaF to give 2 moles of NaF.

That is, 2 moles of NaBr= 2× 103 = 206g

2moles of NaF = 2×42= 84g

If 206g of NaBr yielded 84g of NaF

Therefore 550g of NaBr will yield Xg of NaF

X= 550×84/206

X= 224.27g of NaF

But 42g = 1 mole of NaF

Therefore 224.27g = X mole of NaF

X= 224.27 ×1/42

X is approximately 5moles.

6 0

3 years ago

PLEASE ANSWER ASAP NEED ANSWER!!!!!!!!!!!!!! 75 POINTS

kakasveta [241]

Answer:

The answer to your question is A.

Pure substances can not be broken down into others, so they cannot be molecules

Explanation:

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3 years ago

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10. What is the unit of measurement for the density of a liquid?(need 2)

Vika [28.1K]

Answer:

The measurement would be D=m/v. I do not know what you mean by need two. Can you clarify that for me?

Explanation:

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3 years ago

Convection currents are driven by differences in?

emmasim [6.3K]

Answer:

Density

Explanation:

The density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume: {\displaystyle \rho ={\frac {m}{V}}} where ρ is the density, m is the mass, and V is the volume

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3 years ago

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