PLEASE HELP ME If a radioactive substance has an initial mass of 50 grams

Chemistry

1 answer:

Yuri [45]3 years ago

3 0

Answer: $3.125\ g$

Explanation:

Given

Initial mass $A_o=50\ g$

half-life is $T_{\frac{1}{2}}=5\ years$

At any time the left amount is given by

$A=A_o2^{-\dfrac{t}{T_{\frac{1}{2}}}}\\\\\text{Insert the values}\\\\A=50\cdot 2^{-\dfrac{20}{5}}\\\\A=50\cdot 2^{-4}\\\\A=\dfrac{50}{16}\\\\A=3.125\ g$

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Measurements show that the enthalpy of a mixture of gaseous reactants increases by 319kJ during a certain chemical reaction, whi

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Answer:

the change in energy of the gas mixture during the reaction is 227Kj

Explanation:

THIS IS THE COMPLETE QUESTION BELOW

Measurements show that the enthalpy of a mixture of gaseous reactants increases by 319kJ during a certain chemical reaction, which is carried out at a constant pressure. Furthermore, by carefully monitoring the volume change it is determined that -92kJ of work is done on the mixture during the reaction. Calculate the change of energy of the gas mixture during the reaction in kJ.

From thermodynamics

ΔE= q + w

Where w= workdone on the system or by the system

q= heat added or remove

ΔE= change in the internal energy

q=+ 319kJ ( absorbed heat is + ve

w= -92kJ

If we substitute the given values,

ΔE= 319 + (-92)= 227 Kj

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