Give the example of spontaneous reactions requiring initiation

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

The heat of atomization of methane and ethane are

360 kJ {mol}^{- 1}

and

620 kJ {mol}^{- 1}

, respectively. The longest wavelength of light capable of breaking the

C - C

bond is (Avogadro's number

= 6.023 \times 10^{23}, h = 6.62 \times 10^{- 34} J s

)

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

The process with negative entropy change is:

EASY

Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

The heat of combustion of carbon to

C O_{2}

is

- 393.5 kJ / mol

. The heat released upon the formation of

35.2 g

of

C O_{2}

from carbon and oxygen gas is

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

Given:

C (graphite) + O_{2} (g) \to {CO}_{2} (g); Δ_{r} H^{o} = - 393 .5 kJ {mol}^{- 1}

H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l); Δ_{r} H^{o} = - 285 .8 kJ {mol}^{- 1}

{CO}_{2} (g) + 2 H_{2} O (l) \to {CH}_{4} (g) + 2 O_{2} (g); Δ_{r} H^{o} = + 890 .3 kJ {mol}^{- 1}

Based on the above thermochemical equations, the value of

Δ_{r} H^{o}

at

298 K

for the reaction

C (graphite) + 2 H_{2} (g) \to {CH}_{4} (g)

will be:

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

One mole of an ideal gas at

300 K

in thermal contact with its surroundings expands isothermally from

1.0 L

to

2.0 L

against a constant pressure of

3.0 atm

. In this process, the change in entropy of the surroundings

(∆ S_{s u r r})

in

J K^{- 1}

is:

(1 L atm = 101.3 J)

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

For which of the following processes,

∆ S

is negative?

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

Given:

(i)

C (graphite) + O_{2} (g) \to {CO}_{2} (g);

{ΔrH}^{Θ} = x kJ {mol}^{- 1}

(ii)

C (graphite) + \frac{1}{2} O_{2} (g) \to CO (g);

{ΔrH}^{Θ} = y kJ {mol}^{- 1}

(iii) CO (g) + \frac{1}{2} O_{2} (g) \to {CO}_{2} (g);

{ΔrH}^{Θ} = z kJ {mol}^{- 1}

Based on the above thermochemical equations, find out which one of the following algebraic relationships is correct?

EASY

Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

Given

NO (g) + O_{3} (g) \to {NO}_{2} (g) + O_{2} (g) ∆ H = - 198 .9 kJ / mol

O_{3} (g) \to 3 / 2 O_{2} (g) ∆ H = - 142 .3 kJ / mol

O_{2} (g) \to 2 O (g) ∆ H = + 495 .0 kJ / mol

The enthalpy change

(∆ H)

for the following reaction is

N O (g) + O (g) \to N O_{2} (g)

EASY

Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

The correct thermodynamic conditions for the spontaneous reaction at all temperatures is:

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

A process has

Δ H = 200 J m o l^{- 1}

and

Δ S = 40 J K^{- 1} m o l^{- 1} .

Out of the values given below choose the minimum temperature above which the process will be spontaneous:

EASY

Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

Identify the INVALID equation.

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

For a spontaneous process,

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

One mole of ethanol is produced reacting graphite,

H_{2}

and

O_{2}

together. The standard enthalpy of formation is

- 277.7 k J m o l^{- 1} .

Calculate the standard enthalpy of the reaction when

4

moles of graphite is involved

EASY

Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

For a sample of perfect gas, when its pressure is changed isothermally from

p_{i}

to

p_{f}

, the entropy change is given by

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

The standard enthalpies of formation of ${CO}_{2} (g)$ $, H_{2} O (l)$ and glucose (s) at $2 5^{o} C$ are $- 400 kJ / mol$ , $- 300 kJ / mol$ and $- 1300 kJ / mol$ , respectively. The standard enthalpy combustion per gram of glucose at $2 5^{o} C$ is

( ${ΔH}_{f}^{0} = - 1300 kJ {mol}^{- 1}$ for Glucose)

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

For a reaction,

A (g) \to A (l); ΔH = - 3 RT .

The correct statement for the reaction is

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

The enthalpy change on freezing of

1 mol

of water at

5 ° C

to ice at

- 5 ° C

is:

(Given

Δ_{fus} H = 6 kJ {mol}^{- 1}

at

0 ° C,

C_{p} (H_{2} O, l) = 75 .3 J {mol}^{- 1} K^{- 1}

C_{p} (H_{2} O, s) = 36 .8 J {mol}^{- 1} K^{- 1}

)

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Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

The entropy change associated with the conversion of

1 k g

of ice at

273 K

to water vapours at

383 K

is:

(Specific heat of water liquid and water vapour are

4.2 k J K^{-}

and

2.0 k J K^{- 1} k g^{- 1}

; heat of liquid fusion and vaporization of water are

334 k J k g^{- 1}

and

2491 k J k g^{- 1}

, respectively). (

l o g

273 = 2.436, \log 373 = 2.572, \log 383 = 2.583

)

EASY

Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

At what temperature, a chemical reaction will have following values?

$ΔG = 4 kJ, ΔH = - 60 kJ, ΔS = - 160 J$

EASY

Physical Sciences>Matter and Its Interactions>Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.>Chemical Reactions - The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

For spontaneous polymerisation, which of the following is (are) correct?

Give the example of spontaneous reactions requiring initiation.

Important Questions on Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

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