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2 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]2 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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Vedmedyk [2.9K]

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2 years ago

Exactly 1.0 mol N2O4 is placed in an empty 1.0-L container and allowed to reach equilibrium described by the equation N2O4(g) 2N

Amanda [17]

Answer : The correct option is, (a) 0.44

Explanation :

First we have to calculate the concentration of $N_2O_4$ .

$\text{Concentration of }N_2O_4=\frac{\text{Moles of }N_2O_4}{\text{Volume of solution}}$

$\text{Concentration of }N_2O_4=\frac{1.0moles}{1.0L}=1.0M$

Now we have to calculate the dissociated concentration of $N_2O_4$ .

The balanced equilibrium reaction is,

$N_2O_4(g)\rightleftharpoons 2NO_2(aq)$

Initial conc. 1.0 M 0

At eqm. conc. (1.0-x) M (2x) M

As we are given,

The percent of dissociation of $N_2O_4$ = $\alpha$ = 28.0 %

So, the dissociate concentration of $N_2O_4$ = $C\alpha=1.0M\times \frac{28.0}{100}=0.28M$

The value of x = $C\alpha$ = 0.28 M

Now we have to calculate the concentration of $N_2O_4\text{ and }NO_2$ at equilibrium.

Concentration of $N_2O_4$ = 1.0 - x = 1.0 - 0.28 = 0.72 M

Concentration of $NO_2$ = 2x = 2 × 0.28 = 0.56 M

Now we have to calculate the equilibrium constant for the reaction.

The expression of equilibrium constant for the reaction will be:

$K_c=\frac{[NO_2]^2}{[N_2O_4]}$

Now put all the values in this expression, we get :

$K_c=\frac{(0.56)^2}{0.72}=0.44$

Therefore, the equilibrium constant $K_c$ for the reaction is, 0.44

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2 years ago

24 how many moles are in 2.04 × 1024 molecules of h2o?

Sergeeva-Olga [200]

The answer is 3.39 mol.

Avogadro's number is the number of molecules in 1 mol of substance.
6.02 × 10²³ molecules per 1 mol.
2.04 × 10²⁴ molecules per x.

6.02 × 10²³ molecules : 1 mol = 2.04 × 10²⁴ molecules : x
x = 2.04 × 10²⁴ molecules * 1 mol : 6.02 × 10²³ molecules
x = 2.04/ 6.02 × 10²⁴⁻²³ mol
x = 0.339 × 10 mol
x = 3.39 mol

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2 years ago

How does the equilibrium change to counter the removal of A in this reaction? A + B ⇌ AB

atroni [7]

To counter the removal of A the equilibrium change by shifting toward the left

explanation

If the reaction is at equilibrium and we alter the condition a new equilibrium state is created

The removal of A led to the shift of equilibrium toward the left since it led to less molecules in reactant side which favor the backward reaction.( equilibrium shift to the left)

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2 years ago

Read 2 more answers

An unknown compound melting at 131 - 133 C. It is thought to be one of the following compounds: trans-cinnamic acid (133-134); b

Vesnalui [34]

Answer:

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Explanation:

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X 131 - 133

trans-cinnamic 133 - 134 110 - 120

acid

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malic acid 131 -133 114 -124

Benzoin 135 - 137 108 - 116

The compound X is benzamide since the melting point range is the one closest to this compound ( 130-132 ºC)

The reason there is not an exact match is not due due to the presence of impurities. The presence of impurities always lower the melting point ( it is a coligative property such as the melting point depresion of salt and water )

The reason for the deviation must be be some other factors such as preparation of the sample in the capillary, errors in reading the thermometer, rate of heating, etc.

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2 years ago