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Trava [24]
3 years ago
5

Who had the idea to study humans as groups rather than as individuals?

Chemistry
2 answers:
Ratling [72]3 years ago
7 0

The answer is Malthus, A

Vedmedyk [2.9K]3 years ago
6 0
<span><span>V. C. Wynne-Edwards and Konrad Lorenz were the first authors to raise the concept of altruism</span><span>. This was later reiterated by  </span>David Sloan Wilson, E. O. Wilson and Elliott Sober<span> in 1994 whose works referred to social organisms such as ants</span></span>.




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Strontium-90 is a radioisotope that will decrease in mass by one-half every 29 years. How many years will it take for a 10.0-gra
Lelechka [254]

Answer: It will take 29 years for a 10.0-gram sample of strontium-90 to decay to 5.00 grams

Explanation:

Radioactive decay process is a type of process in which a less stable nuclei decomposes to a stable nuclei by releasing some radiations or particles like alpha, beta particles or gamma-radiations. The radioactive decay follows first order kinetics.

Half life is the amount of time taken by a radioactive material to decay to half of its original value.

Half life is represented by t_{\frac{1}{2}

t_{\frac{1}{2}=\frac{0.693}{\lambda}

\lambda = rate constant

Given : Strontium-90 decreases in mass  by one-half every 29 years , that is half life of Strontium-90  is 29 years.

As half life is independent of initial concentration, it will take 29 years for a 10.0-gram sample of strontium-90 to decay to 5.00 grams as the amount gets half.

7 0
3 years ago
For the following reaction, 4.07 grams of aluminum oxide are mixed with excess sulfuric acid. The reaction yields 10.4 grams of
torisob [31]

Answer:

Theoretical yield = 13.7 g

% yield =76 %

Explanation:

For Al_2O_3

Mass of Al_2O_3  = 4.07 g

Molar mass of Al_2O_3  = 101.96 g/mol

The formula for the calculation of moles is shown below:

moles = \frac{Mass\ taken}{Molar\ mass}

Thus,

Moles= \frac{4.07\ g}{101.96\ g/mol}

Moles\ of\ Al_2O_3= 0.0399\ mol

According to the reaction:

Al_2O_3+3H_2SO_4\rightarrow Al_2(SO_4)_3+3H_2O

1 mole of Al_2O_3  on reaction produces 1 mole of Al_2(SO_4)_3

So,  

0.0399 mole of Al_2O_3  on reaction produces 0.0399 mole of Al_2(SO_4)_3

Moles of Al_2(SO_4)_3  obtained = 0.0399 mole

Molar mass of Al_2(SO_4)_3 = 342.2 g/mol

The formula for the calculation of moles is shown below:

moles = \frac{Mass\ taken}{Molar\ mass}

Thus,

0.0399= \frac{Mass}{342.2\ g/mol}

Mass= 13.7\ g

<u>Theoretical yield = 13.7 g</u>

The expression for the calculation of the percentage yield for a chemical reaction is shown below as:-

\%\ yield =\frac {Experimental\ yield}{Theoretical\ yield}\times 100

Given , Values from the question:-

Theoretical yield = 13.7 g

Experimental yield = 10.4 g

Applying the values in the above expression as:-

\%\ yield =\frac{10.4}{13.7}\times 100

<u>% yield =76 %</u>

6 0
2 years ago
The molecular mass of a substance refers to the:
ololo11 [35]

Answer:

A

Explanation:

it's the sum of the masses of all the atoms in the molecule

please like and Mark as brainliest

3 0
3 years ago
Why is Mg++ smaller than Mg atom?​
Evgen [1.6K]

Answer:

The magnesium ion is much smaller than the magnesium atom because magnesium atom contains more electrons as compared to magnesium ion. Explanation: ... Whereas when an atom tends to lose an electron then it acquires a positive charge and size of the atom tends to increase.

7 0
3 years ago
Read 2 more answers
HELP WILL GIVE BRAINLIEST
DaniilM [7]
The presence of enzymes
7 0
3 years ago
Read 2 more answers
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