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3 years ago

3.) A 208 g sample of sodium-24 decays to 13.0 g of sodium-24 within 60.0 hours.

Chemistry

1 answer:

Ulleksa [173]3 years ago

3 0

Answer:

Half life = 12 hrs

Explanation:

Given data:

Total amount of sample = 208 g

Amount left after 60 hr = 13.0 g

Half life = ?

Solution:

Step one:

amount half life

208 g time 0

208/2 1 half life

104/2 2 half life

52/2 3 half life

26/2 4 half life

13 5 half life

Step 2:

half life = elapsed time/ total half life when 13 g is left

Half life = 60 hrs/ 5

Half life = 12 hrs

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2 years ago

Calculate Delta G for each reaction using Delta Gf values: answer kJ ...thank you

Leni [432]

Answer:

a) $\Delta G=2.6kJ$

b) $\Delta G=-979.57kJ$

c) $\Delta G=264.21kJ$

Explanation:

Hello,

In this case, in each reaction we must subtract the Gibbs free energy of formation the reactants to the Gibbs free energy of formation of the products considering each species stoichiometric coefficients. In such a way, the Gibbs free energy of formations are:

$\Delta _fG_{H_2}=\Delta _fG_{I_2}=0kJ/mol\\\Delta _fG_{HI}=1.3kJ/mol\\\Delta _fG_{CO_2}=-394.4kJ/mol\\\Delta _fG_{CO}=-137.3 kJ/mol\\\Delta _fG_{NH_3}=16.7 kJ/mol\\\Delta _fG_{HCl}=-95.3kJ/mol\\\Delta _fG_{MnO_2}=465.37kJ/mol\\\Delta _fG_{Mn}=0kJ/mol\\\Delta _fG_{NH_4Cl}=-342.81kJ/mol$

So we proceed as follows:

$\Delta G=2\Delta _fG_{HI}-\Delta _fG_{H_2}-\Delta _fG_{I_2}\\\\\Delta G=2*1.3\\\\\Delta G=2.6kJ$

$\Delta G=\Delta _fG_{Mn}+2*\Delta _fG_{CO_2}-\Delta _fG_{MnO_2}-2*\Delta _fG_{CO}\\\\\Delta G=0+2*-394.4-465.37-2*-137.3\\\\\Delta G=-979.57kJ$

$\Delta G=\Delta _fG_{NH_3}+\Delta _fG_{HCl}-\Delta _fG_{NH_4Cl}\\\\\Delta G=16.7-95.3-(-342.81)\\\\\Delta G=264.21kJ$

Regards.

6 0

3 years ago

The weight of the body in the air is .... the weight of the submerged body

stira [4]

Answer:

the correct answer is option 'b': More than

Explanation:

The 2 situations are represented in the attached figures below

When an object is placed in air it is acted upon by force of gravity of earth which is measured as weight of the object.

While as when any object is submerged partially or completely in any fluid the fluid exerts a force in upward direction and this force is known as force of buoyancy and it's magnitude is given by Archimedes law as equal to the weight of the fluid that the body displaces, hence the effective force in the downward direction direction thus the apparent weight of the object in water decreases.