1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Anni [7]
2 years ago
5

A sample taken from a layer of mica in a canyon has 2.10 grams of potassium-40. A test reveals it to be 2.6 billion years old. H

ow much potassium-40 was in the sample originally if the half-life of potassium-40 is 1.3 billion years?
Chemistry
1 answer:
DanielleElmas [232]2 years ago
7 0

Answer:

\boxed{ \text{8.40 g}} 

Explanation:

The half-life of K-40 (1.3 billion years) is the time it takes for half of it to decay.  

After one half-life, half (50 %) of the original amount will remain.  

After a second half-life, half of that amount (25 %) will remain, and so on.  

We can construct a table as follows:  

 No. of                                 Fraction

<u>half-lives</u>      <u>    t/yr      </u>       <u>Remaining</u>  

      0               0                          1

      1                1.3  billion              ½

      2              2.6                          ¼

      3              3.9                          ⅛

We see that after 2 half-lives, ¼ of the original mass remains.

Conversely, if two half-lives have passed, the original mass must have been four times the mass we have now.

Original  mass = 4 × 2.10 g = \boxed{ \text{8.40 g}}

You might be interested in
The Hanunoo people of the Philippines have 92 words for rice, Arabs have 250 words for camel, and people in English-speaking cou
docker41 [41]

Answer:

The correct approach will be the "Linguistic-relativity hypothesis".

Explanation:

  • This theory can be defined as either the Hypothesis of Sapir-Whorf. This theory proposes whether our cognitive capabilities are influenced by languages as well as decide how we start behaving and communicate throughout society.  
  • Sapir Whorf explains these variations throughout the nature of human language throughout the manner a person understands the world.
3 0
3 years ago
Three common ores of iron are FeO, Fe2O3, and Fe3O4. Iron ores are often reduced to elemental iron by heating in the presence of
brilliants [131]

Answer:

Answers are explained below

Explanation:

(a)

Oxidation number of iron :

FeO = +2

Fe2O3= +3

Fe3O4 = +2 and +3 since Fe3O4 is the mixture of FeO and Fe2O3.

(b) FeO + CO ----> Fe (s) + CO2

(c) In a pure iron metallic bond is exist between the particles of Fe. But in the form of ore metals forms ionic bond with the non-metals.

Hence the properties vary.

Yes carbon steel has greater strength than that of pure iron but retains the property of iron because no chemical reaction occurs between carbon and iron.

d)

Mixing of carbon in iron is a type of physical change since there is no chemical reactions occur between the carbon and iron. Carbon atoms diffuses in the place between the iron atoms.

(f) One of the property of non-metals are brittleness. It is non ductile .

So when the percentage of carbon increases its atoms also occupying more and more free places.

And increasing the brittleness. So the iron becomes less ductile.

e)

6 0
3 years ago
Lewis acids and bases are most closely associated with which process?
Evgen [1.6K]
<span>Lewis acids and bases are most closely associated with ELECTRON TRANSFER. A Lewis acid is defined as as a chemical specie that can accept an electron pair from a Lewis base to form a Lewis adduct while a Lewis base is defined as a specie which can donate an electron pair to a Lewis acid or an acceptor compound. Thus, Lewis base and acid has to do with electrons transfer.</span>
8 0
2 years ago
Read 2 more answers
Calculate and explain (in words) how you would make 90.0 mL of 2.0 M MgSO4 solution from a solid solute MgSO4.
lozanna [386]

Answer:

See Below.

Explanation:

Recall that molarity is defined by moles of solute over liters of solution (mol/L).

Therefore, to make 90.0 mL of 2.0 M MgSO₄, we will need:

\displaystyle 90.0\text{ mL} \cdot \frac{2.0\text{ mol MgSO$_4$}}{1\text{ L}} \cdot \frac{1\text{ L}}{1000\text{ mL}} = 0.18\text{ mol MgSO$_4$}

Convert this amount to grams. The molecular weight of MgSO₄ is 120.38 g/mol:

\displaystyle 0.18\text{ mol MgSO$_4$} \cdot \frac{120.38\text{ g MgSO$_4$}}{1\text{ mol MgSO$_4$}} = 22\text{ g MgSO$_4$}

Therefore, to make the solution, we can add 22 grams of MgSO₄ into a graduated cylinder, then mix and dilute the solution with distilled water until we reach 90.0 mL.

5 0
1 year ago
Read 2 more answers
How many moles of oxygen (O) atoms are in a sample of 3.98 × 1023 atoms? 0.661 mol O 1.51 mol O 6.60 × 1022 mol O 2.40 × 1047 mo
lidiya [134]
To find moles from any number of atoms, always divide by the constant called Avogadro's Number. This number is representative of the number of atoms or molecules in a mole of any substance and is equal to about 6.022* 10^{23} &#10;.

So, for this problem, we take the number of atoms of oxygen and divide by Avogadro's Number. 

\frac{3.98*  10^{23}  O_{2} atoms  }{6.022*  10^{23} atoms/mol  } = 0.6609 moles

Answer: 0.661 moles (after rounding)

Make sense?
7 0
3 years ago
Other questions:
  • What type(s) of intermolecular forces are expected between seh2 molecules?
    10·2 answers
  • According to the authors, the most effective means of developing _______________ are instrumental chemistry, microscopy, photoma
    7·1 answer
  • Explain how solid naphthalene in mothballs is distributed evenly through clothes in a drawer
    10·1 answer
  • Greg checks his watch one day at noon when the Sun is directly overhead. He decides to check his watch when the Sun is directly
    14·1 answer
  • A neutron walks into a gas station to buy some snacks. He ask the cashier ,"How much"? The cashier replies,"For you? No charge."
    14·1 answer
  • if a 40 kg person is accelerating at m/s^2,then the magnitude of force acting on him or her 400 N? true or false
    14·1 answer
  • When the average kinetic energy of a gas is increased, the motion of the gas particles
    11·1 answer
  • What is the numerical value of KcKc for the reaction if the concentrations at equilibrium are 0.10 MM SO2SO2, 0.18 MM O2O2, and
    10·1 answer
  • Please show all work for full credit.
    9·1 answer
  • A compound contains 72% magnesium and 28% nitrogen. What is its empirical formula?
    12·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!