Given :
Half-life of Iodine , [tex]t_{0.5}=8 \ days[/tex] .
Initial concentration , [tex][A_o]=100\ mg[/tex] .
To Find :
The amount of sample remains after 32 days .
Solution :
Rate constant is given by :
[tex]k=\dfrac{0.693}{t_{0.5}}\\\\k=\dfrac{0.693}{8}\ s^{-1}\\\\k=0.086625\ s^{-1}[/tex]
Now , by rate law :
[tex][A]=[A_o]e^{-kt}[/tex]
Putting all given values, we get :
[tex][A]=100\times e^{-(0.086625)\times 32}\\[/tex]
[tex][A]=6.25\ mg[/tex]
Therefore , the remaining sample after 32 days is 6.25 mg .
Hence , this is the required solution .
Need help with this
Answer:
Its enviormental science because enviormental science is an interdisciplinary academic field that integrates physical.
A sample of seawater weighs 250 g and has a volume of 173 ml. What is the density of seawater?
Answer:
The answer is 1.45 g/mLExplanation:
The density of a substance can be found by using the formula
[tex]density = \frac{mass}{volume} \\ [/tex]
From the question
mass of seawater = 250 g
volume = 173 mL
It's density is
[tex]density = \frac{250}{173} \\ = 1.4450867052...[/tex]
We have the final answer as
1.45 g/mLHope this helps you
why is it important to conduct scientific tests more than one time
Answer:
you man get different results
the following statement is an example of "if i post a image on Instagram at 7:00 pm, then ill get the most likes a. hypothesis b. problem c. experiment d. independent variable
I NEED HELP NOW PLEASE HELP ME AS FAST AS U CAN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Answer:
a
Explanation:
The given statement if i post a image on social media at 7:00 pm, then ill get the most likes is a hypothesis.
What is hypothesis?
Hypothesis can be defined as an assumption which is made for the sake of argument . It is an interpretation of a practical condition for which action needs to be taken.It is defined as a tentative assumption which is made to test logical consequences.It is an antecedent clause of a statement which is conditional.
It is constructed before research. There are six types of hypothesis 1)simple hypothesis 2) complex hypothesis 3) directional hypothesis 4)non-directional hypothesis 5) null hypothesis 6)casual hypothesis
The hypothesis should be clear and precise, it must be specific and way of explanation of hypothesis should be simple.
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I need help please, will give 5 stars
What is the formula for Hydroxide
Answer:
OH-
Explanation:
it's consists of an oxygen and hydrogen atom held together by a covalent bond and carries a negative electric charge
Give me a hand，Solve this problem，Need everyone's help
Answer:
A. 8.8 g.
B. 5.3 g.
C. 449 g.
Explanation:
A. Determination of the mass of CO2.
Mole of CO2 = 0.2 mole
Molar mass of CO2 = 12 + (2×16)
= 12 + 32
= 44 g/mol
Mass of CO2 =?
Mole = mass /Molar mass
0.2 = mass of CO2 /44
Cross multiply
Mass of CO2 = 0.2 × 44
Mass of CO2 = 8.8 g
B. Determination of the mass of Na2CO3.
Mole of Na2CO3 = 0.05 mole
Molar mass of Na2CO3 = (2×23) + 12 + (3×16)
= 46 + 12 + 48
= 106 g/mol
Mass of Na2CO3 =?
Mole = mass /Molar mass
0.05 = mass of Na2CO3 /106
Cross multiply
Mass of Na2CO3 = 0.05 × 106
Mass of Na2CO3 = 5.3 g
C. Determination of the mass of Fe(OH)2.
Mole of Fe(OH)2 = 5 moles
Molar mass of Fe(OH)2 = 55.8 + 2(16 + 1)
= 55.8 + 2(17)
= 55.8 + 34
= 89.8 g/mol
Mass of Fe(OH)2 =?
Mole = mass /Molar mass
5 = mass of Fe(OH)2/89.8
Cross multiply
Mass of Fe(OH)2 = 5 × 89.9
Mass of Fe(OH)2 = 449 g.
How are elements with atomic masses greater than Uranium’s made?
Answer:Atoms heavier that uranium do not exist in nature.they must be synthesized in a particle accelerator
Explanation:
Jessica poured a liquid into the graduated cylinder below. What is the volume of the liquid?
Answer:
Answer is B
Explanation:
1
How many significant figures are there in 9,000,500 mL?
How are the molecules in the cell membrane arranged? as a lipid bilayer as a protein bilayer as a carbohydrate bilayer as a DNA bilayer
Answer:
as a lipid bilayer
Explanation:
just took the test
Answer:
A. as a lipid bilayer
Calculate the destiny of the object that has a mass of 453 g and occupies the volume of 225 cm3
A ( 2.01g/cm3
B( 5.00 g/cm3
C( 453 g/cm3
D( 228 g/cm3
density = 2.013g/cm3
Explanation:
density = mass/volume
density = 453g/225cm3
density = 2.013g/cm3
What is the density of 19 milliliters of a liquid substance with a mass of 6.05 grams?
Answer:
The answer is
0.32 g/mLExplanation:
The density of a substance can be found by using the formula
[tex]density = \frac{mass}{volume} [/tex]From the question
mass = 6.05 g
volume = 19 mL
The density of the substance is
[tex]density = \frac{6.05}{19} \\ = 0.3184210526...[/tex]
We have the final answer as
0.32 g/mLHope this helps you
Which phrase best describes igneous rocks?
form when lava and magma cool
accumulate sediments following erosion
require heat and pressure to be formed
consist of many sediment layers
Answer:form when magma and lava cool :/
Explanation:hope this helps, and I’m this because ingenious rocks are made/ formed from magma and lava.
The phrase which best describes igneous rocks is option A, .i.e., it forms when lava and magma cool.
What is igneous rock?Igneous rocks are formed by the melting of earth's crust into magma, . The two types of this rocks are, Extrusive and intrusive igneous rocks . The slow cooling of magma beneath the surface results in intrusive igneous rock.
Magma in the crystal is in molten liquid state which heat by convection and flows out. This creates slight movement in plates and the hot mantle the cools down to form igneous crystals.
Extrusive igneous rock is created when lava above the surface cools quickly. The magma hardens more quickly after being brought to the surface via cracks or volcanic explosions. As a result, these rocks are crystalline, smooth, and fine-grained.
Thus regarding the formation of igneous rocks, option A is correct.
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Why carbon dioxide can be tested with the help of moist blue litmus paper ?
Answer:
carbon dioxide is acidic and when it comes in contact with blue litmus paper it turns red
Explanation:
Scientists use results from new experiments to
support their own personal political opinions.
increase precision of data that were collected previously.
modify existing explanations of how nature works.
aid in distinguishing science from pseudoscience.
Answer:
modify existing explanations of how nature works.
Explanation:
Scientists use new experiments to aid in distinguishing science from pseudoscience also to update the explanations of how nature works.
What is pseudoscience?Pseudoscience is the falls assumptions and predictions by some thoughts and prejudice that arguing to be scientific. For example astrology, there is no scientific evidence for that,
Scientists update the phenomenon and concepts in nature through various research works which are planed in advanced level. These results are not for personal requirements not for political opinions.
Thus new experiments are conducting for arriving at new information that are valuable to everyone and thus distinguishing science from pseudoscience.
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How many joules of heat are needed to raise the temperature of 10.0 g of aluminum from 22°C to 55°C, if the specific heat of aluminum is 0.90 J/g°C?
Answer:
0.90 degree C
Explanation:
The key to this problem lies with aluminium's specific heat, which as you know tells you how much heat is needed in order to increase the temperature of 1 g of a given substance by 1∘C
In your case, aluminium is said to have a specific heat of
0.90 J g∘ C.
What would be the charge of an ion with 9 protons, 10 neutrons, 10 electrons
Answer:
negative
Explanation:
Any atom whose number electrons are more than the number of protons in it will have a negative charge. Since in this case the electrons are 10 and protons are 9 the 9+ charge protons and 9- charge electrons cancel each other giving a final charge of negative.
The charge of an ion with 9 protons and 10 electrons and neutrons is -1 as there is one more electron in comparison to number of protons .
What is an ion?An ion is defined as an atom or a molecule which has a net electrical charge. There are 2 types of ions :1) cation 2) anion . The cation is the positively charged ion and anion is the negatively charged ion . As they are oppositely charged they attract each resulting in the formation of ionic bond.
Ions consisting of single atom are mono-atomic ions while which consists of two or more ions are called as poly-atomic ions . They are created by chemical interactions . They are very reactive in their gaseous state and rapidly react with oppositely charged ions resulting in neutral molecules.They are attracted to opposite charges.
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2. You water three sunflower plants with salt water. Each plant receives a different
concentration of salt solutions. A fourth plant receives pure water. After a
two-week period, the height is measured.
IV
I
DV
CG
Answer:
Independent variable, is the amount of salt water received by each plant
Dependent variable, is the height of each plant
Control group, is the fourth plant that received pure water.
Note: The question is incomplete. The complete question is as follows: For the following experiments, define the independent variable (IV), dependent variable (DV) and control group (CG).
2. You water three sunflower plants with salt water. Each plant receives a different concentration of salt solutions. A fourth plant receives pure water. After a two-week period, the height is measured.
Explanation:
Independent variable: An independent variable is a variable that an experimenter changes or controls and which has a direct effect on the dependent variable.
In the experiment above, the independent variable is the amount of salt water received by each plant because it is under the control of the experimenter and also is thought to have a direct effect on the height of plants.
Dependent variable: A dependent variable is a variable that is being measured or studied in an experiment, and it depends on the independent variable for its results.
The height of the plants is the dependent variable as it depends on the amount of salt water the plant receives.
Control group: The control group is the group in an experiment or study that does not receive the treatment as the other groups being studied and as such, is not influenced by the independent variable. Therefore, it is used as a standard for the other groups under study.
In this experiment, the control group is the fourth plant that received pure water.
2. Which set of symbols represents isotopes of the same element?
Set 2
Set 1
80
м
38
133
81
M
38
83
M
38
132
Q
55
Q
133
Q
54
55
Set 4
Set 3
50
L
19
50
L
20
50
L
21
91
J
43
92
J
42
93
J
42
The set of symbols that represents isotopes has been 84/38 M 86/38 M 87/38 M. Thus, option D is correct.
The isotopes are the elements with same atomic number, but different mass number. In an isotope [tex]\rm ^a_bX[/tex], a has been the atomic mass, and b has been the atomic number.
The isotopes will have same value for b, while different values for a.
In the following given sets:
A. 50/19 L 50/20 L 50/21 L
It has same number of mass the atomic number has been different. Thus, the set not represents isotopes.
B. 138/59 Q 133/55 Q 133/54 Q
The given elements, has different atomic number, and different mass number. Thus the set did not represents the isotopes.
C. 91/42 J 92/42 J 93/40 J
The given elements, has different atomic number, and different mass number.Thus the set did not represents the isotopes.
D. 84/38 M 86/38 M 87/38 M
The given set has same atomic number with different mass number.Thus, the set has been the representation of isotopes.
The set of symbols that represents isotopes has been 84/38 M 86/38 M 87/38 M. Thus, option D is correct.
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How many penicillin molecules would you have if you had a total of 36 hydrogen atoms? What would be the total atomic mass?
Answer:
Explanation:
Molecular formula of penicillin = C₁₆ H₁₈ N₂ O₄S
No of hygrogen atoms = 36
No of molecules = 36 / 18 = 2
molecular weight = 334 amu
molecular weight of 2 molecules = 334 x 2 = 668 amu.
This beaker is filled with three liquids of different colors and densities. Which color substance is the most dense? How do you know
Answer:
the one at the bottom
Explanation:
the more dense an object is in this kind of demonstration (which is called a density tower btw) the lower it'd be so taking this reason into consideration the lowest would be the densest
Daniel needed 5.0 x 10 3mm of copper wire for his senior year science project. When Daniel went to the hardware store, he noticed that the unit of measure used for the wire was meters. Calculate the length, in meters, of copper wire Daniel needed for his project.
Answer:
if its 5X 10^3 mm=5m and if its 5X 10^-3 mm=5X 10^-6m
Explanation:
we know,
1m= 1000mm
as given 5X 10^3 mm we have to convert to meter
now 5X 10^3 mm= 5X 10^3/1000=5m
but if its 5X 10^-3 mm= 5X 10^-3/1000= 5X 10^-6m
thank u,
Which of the following questions can be answered by science? (5 points)
Answer:
you didn't put the question
Explanation:
??
Answer:
I. Why is land use more important than water use?
II. Why do human activities affect land?
Explanation:
Which of the following is true about scarcity?
Answer:
It would be
a) Scarcity affects all societies.
. Select one resource and hypothesize what side effects might
occur if that
resource is depleted.
A scientist observes that the electric resistance of a superconducting material drops to zero when the material is cooled to very low temperatures which of the following statements best describe what the scientist is observing
Answer: The scientist is observing an intensive property of a superconductor. ( So C)
Explanation: edu
Answer: the scientist is observing an intensive property of a superconductor.
54.29
Which statement describes an atomic nucleus?
O An atomic nucleus is negatively charged.
O An atomic nucleus has no electrical charge.
O An atomic nucleus consists of mostly empty space.
O An atomic nucleus contains most of the atom's mass.
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Which element has an atomic mass of 106.42?
Answer:
carbon
Explanation:
The element which has atomic mass of 106.42 is carbon as per the existing isotopes.
What is an element?
It is defined as a substance which cannot be broken down further into any other substance. Each element is made up of its own type of atom. Due to this reason all elements are different from one another.
Elements can be classified as metals and non-metals. Metals are shiny and conduct electricity and are all solids at room temperature except mercury. Non-metals do not conduct electricity and are mostly gases at room temperature except carbon and sulfur.
The number of protons in the nucleus is the defining property of an element and is related to the atomic number.All atoms with same atomic number are atoms of same element.
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Match the scientist to his contribution to the atomic theory - Thomson - Rutherford - Bohr A. Electron energy levels B. Nucleus C. Electrons
Answer: Thomson - C
Rutherford - B
Bohr - A
Explanation: I just took the quiz