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3 years ago

What does a scientific law do ?

Chemistry

1 answer:

baherus [9]3 years ago

3 0

Answer:

Scientific laws or laws of science are statements, based on repeated experiments or observations, that describe or predict a range of natural phenomena.

Explanation:

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Give the name of the reaction that achieves the theoretical limits with respect to free energy in thermodynamics.a. reversible r

Assoli18 [71]

Answer:

The correct option is: a. reversible reaction

Explanation:

In thermodynamics, Gibb's free energy is the quantitative measure of the spontaneity or feasibility of a chemical reaction, at fixed temperature and pressure.

It can also be described as the maximum available work obtained from a closed system. This maximum work can only be achieved in a reversible process, at fixed pressure and temperature.

The Gibb's free energy (ΔG) is given by: ΔG = ΔH - T.ΔS

8 0

3 years ago

At 298 K, the osmotic pressure of a glucose solution (C6H12O6 (aq)) is 12.1 atm. Calculate the freezing point of the solution. T

Anarel [89]

Answer: The freezing point of solution is -0.974°C

Explanation:

To calculate the concentration of solute, we use the equation for osmotic pressure, which is:

$\pi=iMRT$

where,

$\pi$ = osmotic pressure of the solution = 12.1 atm

i = Van't hoff factor = 1 (for non-electrolytes)

M = molarity of solute = ?

R = Gas constant = $0.0821\text{ L atm }mol^{-1}K^{-1}$

T = temperature of the solution = 298 K

Putting values in above equation, we get:

$12.1atm=1\times M\times 0.0821\text{ L.atm }mol^{-1}K^{-1}\times 298K\\\\M=\frac{12.1}{1\times 0.0821\times 298}=0.495M$

This means that 0.495 moles of glucose is present in 1 L or 1000 mL of solution

To calculate the mass of solution, we use the equation:

$\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}$

Density of solution = 1.034 g/mL

Volume of solution = 1000 mL

Putting values in above equation, we get:

$1.034g/mL=\frac{\text{Mass of solution}}{1000mL}\\\\\text{Mass of solution}=(1.034g/mL\times 1000mL)=1034g$

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Moles of glucose = 0.495 moles

Molar mass of glucose = 180.16 g/mol

Putting values in above equation, we get:

$0.495mol=\frac{\text{Mass of glucose}}{180.16g/mol}\\\\\text{Mass of glucose}=(0.495mol\times 180.16g/mol)=89.18g$

Depression in freezing point is defined as the difference in the freezing point of pure solution and freezing point of solution.

The equation used to calculate depression in freezing point follows:

$\Delta T_f=\text{Freezing point of pure solution}-\text{Freezing point of solution}$

To calculate the depression in freezing point, we use the equation:

$\Delta T_f=iK_fm$

Or,

$\text{Freezing point of pure solution}-\text{Freezing point of solution}=i\times K_f\times \frac{m_{solute}\times 1000}{M_{solute}\times W_{solvent}\text{ (in grams)}}$

where,

Freezing point of pure solution = 0°C

i = Vant hoff factor = 1 (For non-electrolytes)

$K_f$ = molal freezing point elevation constant = 1.86°C/m

$m_{solute}$ = Given mass of solute (glucose) = 89.18 g

$M_{solute}$ = Molar mass of solute (glucose) = 180.16 g/mol

$W_{solvent}$ = Mass of solvent (water) = [1034 - 89.18] g = 944.82 g

Putting values in above equation, we get:

$0-\text{Freezing point of solution}=1\times 1.86^oC/m\times \frac{89.18\times 1000}{180.16g/mol\times 944.82}\\\\\text{Freezing point of solution}=-0.974^oC$

Hence, the freezing point of solution is -0.974°C

8 0

3 years ago

How much energy is required to change the temperature of 35.0 g of Lead

Nezavi [6.7K]

Answer:

Q = 270 Joules (2 sig. figs. as based on temperature change.)

Explanation:

Heat Transfer Equation of pure condensed phase substance => Q = mcΔT

Mixed phase (s ⇄ l melting/freezing, or l ⇄ g boiling/condensation) heat transfer equation => Q = m∙ΔHₓ; ΔHₓ = phase transition constant

Since this is a pure condensed phase (or, single phase) form of lead (Pb°(s)) and not melting/freezing or boiling/condensation, one should use

Q = m·c·ΔT

m = mass of lead = 35.0g

c = specific heat of lead = 0.16J/g°C

ΔT = Temp change = 74°C - 25°C = 49°C

Q = (35.0g)(0.16J/g·°C )(49°C) = 274.4 Joules ≅ 270 Joules (2 sig. figs. as based on temperature change.)

7 0

3 years ago

What type of physical change is it when a liquid turns into a solid and a solid turns into a liquid

goblinko [34]

Answer:

Freezing and Melting (Fusion)

Explanation:

4 0

3 years ago

a skateboarder wants to skate down the ramp at a skate park he will want the forces acting on him to be

kvasek [131]

Answer:

increase

Explanation:

At the skate park when a skateboarder wants to skate down a ramp, the skate boarder wishes to move faster and with speed so that it help him to skate more time. This can only be achieved if the all the forces acting on him will increase as he skates down the ramp without much of the frictional force acting on the wheels of the skate board. The less friction force acts on the wheel, the more he can skate with more speed.

Thus, the skateboarder wants the force to be increase that is acting on him.

4 0

3 years ago