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3 years ago

Which of the following is true?

Chemistry

1 answer:

Tomtit [17]3 years ago

3 0

Answer:

a. A reaction in which the entropy of the system increases can be spontaneous only if it is endothermic.

Explanation:

The change in free energy (ΔG) that is, the energy available to do work, of a system for a constant-temperature process is:

$ΔG = ΔH - TΔS$

When ΔG < 0 the reaction is spontaneous in the forward direction.

When ΔG > 0 the reaction is nonspontaneous. The reaction is

spontaneous in the opposite direction.

When ΔG = 0 the system is at equilibrium.

If both ΔH and ΔS are positive, then ΔG will be negative only when the TΔS term is greater in magnitude than ΔH. This condition is met when T is large.

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The graduated cylinder below shows major scale divisions every 5 mL. How should the volume of the liquid be recorded? Use the co

OLga [1]

Explanation:

First, note that the surface of the liquid is curved. This is called the meniscus. This phenomenon is caused by the fact that water molecules are more attracted to glass than to each other (adhesive forces are stronger than cohesive forces). When we read the volume, we read it at the BOTTOM of the meniscus.

The smallest division of this graduated cylinder is 1 mL. Therefore, our reading error will be 0.1 mL or 1/10 of the smallest division. An appropriate reading of the volume is 36.5 0.1 mL. An equally precise value would be 36.6 mL or 36.4 mL.

How many significant figures does our answer have? 3! The "3" and the "6" we know for sure and the "5" we had to estimate a little.

6 0

2 years ago

A 45.0 mL sample of 0.020 M acetic acid (HC2H3O2) is titrated with 0.020 M NaOH.? Determine the pH of the solution after adding

White raven [17]

Answer:

Explanation:

CH₃COOH + NaOH = CH₃COONa + H₂O .

.02M

CH₃COOH = CH₃COO⁻ + H⁺

C xC xC

Ka = xC . xC / C = x² C

1.8 x 10⁻⁵ = x² . .02

x² = 9 x 10⁻⁴

x = 3 x 10⁻²

= .03

concentration of H⁺ = xC = .03 . .02

= 6 x 10⁻⁴ M , volume = 45 x 10⁻³ L

moles of H⁺ = 6 X 10⁻⁴ x 45 x 10⁻³

= 270 x 10⁻⁷ moles

= 2.7 x 10⁻⁵ moles

concentration of NaOH = .0200 M , volume = 35 x 10⁻³ L

moles of Na OH = 2 X 10⁻² x 35 x 10⁻³

= 70 x 10⁻⁵ moles

NaOH is a strong base so it will dissociate fully .

there will be neutralisation reaction between the two .

Net NaOH remaining = (70 - 2.7 ) x 10⁻⁵ moles

= 67.3 x 10⁻⁵ moles of NaOH

Total volume = 45 + 35 = 80 x 10⁻³

concentration of NaOH after neutralisation.= 67.3 x 10⁻⁵ / 80 x 10⁻³ moles / L

= 8.4125 x 10⁻³ moles / L

OH⁻ = 8.4125 x 10⁻³

H⁺ = 10⁻¹⁴ / 8.4125 x 10⁻³

= 1.1887 x 10⁻¹²

pH = - log ( 1.1887 x 10⁻¹² )

= 12 - log 1.1887

= 12 - .075

= 11.925 .

4 0

3 years ago

(b) The mass of a single molybdenum atom is 1.59×10-22 g. Suppose enough Mo atoms were lined up like beads on a string to span a

serious [3.7K]

Answer:N=1151724138 atoms

Explanation:The atomic radius of molybdenum atom is 145 picometers so lining up molybdenum atoms is like lining up the beads of radius 145 picometers

so one bead would cover the length of 145*2=290 picometers

hence the atom's diameter =D=290 picometers

D=290 *10^(-12)

$D=290/1000000000000$

also

Distance span= 33.4 cm

Distance span= 0.334m

As the Distance span adds up with no of atoms the resulting formula is

Distance span by atoms= No of atoms * atom's diameter

$N=\frac{Distance Spaned}{Atom's Diameter } \\N=0.334/(0.000000000290)\\N=1151724138 atoms$

4 0

3 years ago

Which of these solutes raises the boiling point of water the most?

VMariaS [17]

Raising of the boiling point is a colligative property. That means that it depends on the number of particles dissolved. The greater the number of particles the greater the increase in the boiling point. So, you can compare the effect of these solutes in the increase of the boiling point by writing the chemical equations and comparing the number of particles dissolved: 1)ionic lithium chloride, LiCl(s) --> Li(+) + Cl (-) => 2 ions; 2) ionic sodium chloride, NaCl(s) --> Na(+) + Cl(-) => 2 ions; 3) molecular sucrose, C12H22O11 (s) ---> C12H22O11(aq) => 1 molecule; 4) ionic phosphate, Na3PO4 --> 3Na(+) + PO4 (3-) => 4 ions; 5) ionic magnesium bromide, MgBr2 --> Mg(2+) + 2 Br(-) => 3 ions. So, ionic phosphate produces the greatest number of particles and it will cause the greatest increase of the boiling point.

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3 years ago

A molecular biologist measures the mass of cofactor a in an average yeast cell. the mass is 41.5 pg . what is the total mass in

Hitman42 [59]

The unit pg stands for pictogram. It is one-trillionth of a gram. Because of the very small mass, it is expressed in the prefix form of the base units for convenience. Now, the mass of cofactor a is 41.5 pg per cell. Since there are a total of 105 cells, the total mass would be:

Total mass = 105 cells * 41.5 pg/cell = 4,357.5 pg

6 0

3 years ago