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3 years ago

Two facts about calorimetry

Chemistry

1 answer:

blagie [28]3 years ago

8 0

The measure of the quantity of heat exchanged.
Uses many different units of measurements.

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Phthalates used as plasticizers in rubber and plastic products are believed to act as hormone mimics in humans. The value of ΔHc

jeka94

Answer:

$T_f$ = 25.05°C

Explanation:

Given:

the value of ΔHcomb (heat of combustion) for dimethylphthalate (C10H10O4) is = 4685 kJ/mol.

mass = 0.905g of dimethylphthalate

molar mass = 194.18g dimethylphthalate

number of moles of dimethylphthalate = ???

$T_i$ = 21.5°C

$C_{calorimeter}$ = 6.15 kJ/°C

$T_f$ = ???

since we have our molar mass and mass of dimethylphthalate ;we can determine the number of moles as;

0.905g of dimethylphthalate × $\frac{1 mole (dimethylphthalate)}{194.184g(dimethylphthalate)}$

number of moles of dimethylphthalate = 0.000466 moles

Heat released = moles of dimethylphthalate × heat of combustion

= 0.000466 moles × 4685 kJ

= 21.84 kJ

∴ Heat absorbed by the calorimeter = $C_{calorimeter}$ $(T_f-T_i} )$

21.84 kJ =6.15 kJ/°C $* (T_f-21,5^0C)$

21.84 KJ = $(6.15 kJ/^0C * T_f) - (6.15 kJ/^0C*21.5^0C)$

21.84 KJ = $(6.15 kJ/^0C * T_f)$ - 132.225 kJ

21.84 KJ + 132.225 kJ = $(6.15 kJ/^0C * T_f)$

154.065 kJ = $(6.15 kJ/^0C * T_f)$

$T_f$ = $\frac{154.065kJ}{6.15kJ/^0C}$

$T_f$ =25.05°C

4 0

4 years ago

Calculate ∆G ◦ r for the decomposition of mercury(II) oxide 2 HgO(s) → 2 Hg(ℓ) + O2(g) ∆H◦ f −90.83 − − (kJ · mol−1 ) ∆S ◦ m 70.

bagirrra123 [75]

Answer:

4. +117,1 kJ/mol

Explanation:

ΔG of a reaction is:

ΔGr = ΔHr - TΔSr (1)

For the reaction:

2 HgO(s) → 2 Hg(l) + O₂(g)

ΔHr: 2ΔHf Hg(l) + ΔHf O₂(g) - 2ΔHf HgO(s)

As ΔHf of Hg(l) and ΔHf O₂(g) are 0:

ΔHr: - 2ΔHf HgO(s) = 181,66 kJ/mol

In the same way ΔSr is:

ΔSr= 2ΔS° Hg(l) + ΔS° O₂(g) - 2ΔS° HgO(s)

ΔSr= 2* 76,02J/Kmol + 205,14 J/Kmol - 2*70,19 J/Kmol

ΔSr= 216,8 J/Kmol = 0,216 kJ/Kmol

Thus, ΔGr at 298K is:

ΔGr = 181,66 kJ/mol - 298K*0,216kJ/Kmol

ΔGr = +117,3 kJ/mol ≈ 4. +117,1 kJ/mol

I hope it helps!

5 0

3 years ago

Einstein's formula tells us the amount of energy to which a given mass would be equivalent, if it were all suddenly turned into

skad [1K]

Einstein's famous equation, E = mc^2 relates the mass (m) of an object to energy (E). The speed of light (c), is the constant of proportionality. Einstein formulated the equation within his theory of special relativity. Indeed, a physical interpretation of this equation is that any given mass is equivalent to the energy given by the equation, if it were suddenly converted to energy. Therefore the answer to the question is true.

5 0

4 years ago

An 80 kg long jumper in flight accelerates at a rate of 10 m/s^2. What is the force of the long jumper

Katarina [22]

Answer:

F = 800 N

Explanation:

Given data:

Mass = 80 Kg

Acceleration = 10 m/s²

Force = ?

Solution:

Formula:

F = m × a

F = force

m = mass

a = acceleration

Now we will put the values in formula:

F = m × a

F = 80 kg × 10 m/s²

F = 800 kg.m/s²

kg.m/s² = N

F = 800 N

6 0

3 years ago

g modenr vacuum pumps make it easy to attain pressures of the order of in the laboratory. at a preasusure of 6.75 atm and an ord

Ratling [72]

Answer:

Number of molecules = 1.8267×10^20

Explanation:

From the question, we can deuced that the gases behave ideally, the we can make use of the ideal gas equation, which is expressed below;

PV = nRT

where

P =pressure

V =volume

n = the number of moles

R is the gas constant equal to 0.0821 L·atm/mol·K

T is the absolute temperature

Given:

P = 6.75 atm;

T = 290.0 k,

; V = 1.07 cm³ = 0.001 L

( 6.75 atm)(0.00107 L) = n(0.0821 L·atm/mol·K)(290K)

n = 3.0335167*10^-4 moles

But there are 6.022×10²³ molecules in 1 mole,

Number of molecules = 1.8267×10^20

7 0

3 years ago