Chemistry, 10.01.2021 08:30 nnn79

What is the half life if 500 grams decays to 125 grams in 25years?
with steps pls

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Answer from: LudwergTheMyth

The half life of the sample is 60.26 years.

Explanation:

All radioactive decay reactions follow first order reaction.

The formula used to calculate the rate constant for a first order reaction follows:

$k=\frac{2.303}{t}\log \frac{a}{(a-x)}$

where,

k = rate constant = ?

t = time period = 25 years

a = initial concentration of the reactant = 500 g

a - x = concentration of reactant left after time 't' = (500 - 125) = 375 g

Putting values in above equation, we get:

$k=\frac{2.303}{25yrs}\log \frac{500g}{375g}\\\\k=0.0115yr^{-1}$

Now, to calculate the half life period of the reaction, we use the equation:

$t_{1/2}=\frac{0.693}{k}$

where,

$t_{1/2}$ = half life period of the reaction = ?

k = rate constant = $0.0115yr^{-1}$

Putting values in above equation, we get:

$t_{1/2}=\frac{0.693}{0.0115yr^{-1}}\\\\t_{1/2}=60.26yrs$

Hence, the half life of the sample is 60.26 years.

Answer from: Quest

answer: the value of enthalpy change will be -152.80 kj.

solution:

pressure = 1atm , temperature = $25^oc$ = 298 k $)0^oc=273kelvins$

$o_3+3no\rightarrow 3no_2,\delta h_{reaction}=? [/)</p><p>[tex]\delta h_{no}=90.4kj/mol$

$\delta h_{no_2}=33.85kj/mol$

$\delta h_{o_3}=142.2kj/mol$

$\delta h_{reaction}=\sum \delta h_{products}-\sum\delta h_{reactants}=3\times\delta h_{no_2}-(3\times \delta h_{no}+\delta h_{o_3})$

$\delta h_{reaction}=33.85-(90.4+142.2)=-311.85kj/mol$

given that pressure and temperature are same in both gases , the number of moles of both gases can be determined by the ideal gas equation.

$v_{no}=12.00 l,v_{o_3}=8.50 l$

$pv_{no}=n_{no}rt=1atm \times 12.00 l=n_{no}\times 0.0821 atml/k mol \times 298 k$

$n_{no}=0.49 moles$

$pv_{o_3}=n_{o_3}rt=1atm \times 8.50 l=n_{o_3}\times 0.0821 atml/k mol \times 298 k$

$n_{o_3}=0.34 moles$

according to reaction 3 moles no are reacting with 1 mol of $o_3$ ,then 0.49 mol of no will react with $\frac{1}{3}\times 0.49$ moles of ozone that is 0.16 moles of ozone. since, no is limiting reagent and $o_3$ is an excessive reagent.

enthalpy change for the reaction between the given volumes of the gases is :

$\delta h_{reaction}\times \text{moles of no}=-311.85kj/mol\times 0.49 mol=-152.80kj/mol$

Answer from: Quest

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.

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What is the half life if 500 grams decays to 125 grams in 25years?
with steps pls...