There are 5.0g of I-131 left after 40 days. How many grams were in the original sample if the half-life is 8 days?
160 grams of I-131 were in the original sample if the half-life is 8 days.
What do you mean by half life?In a chemical reaction, the time taken for the concentration of that substance to become half of its initial value is called half-life. This term is used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay .
The amount left N after n half lives of a radioactive element with original amount N₀ is given as:
N= N₀ (1/2)ⁿ
Given, half life of Iodine-131 is 8 days
n= 40/8= 5
5= N₀ (1/2)⁵
N= 32 * 5
= 160 grams
Hence, the original amount amount of I-131 will be 160 grams.
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Using your knowledge of symbols, determine which compound listed must contain both copper and oxygen.
1. malachite, Cu 2CO 3(OH) 2
2. calcite, CaCO 3
3. glucose, C 6H 12O 6
4. chalcopyrite, CuFeS 2
Answer:
Malachite
Explanation:
Malachite is the only listed compound that must contain copper and oxygen.
Copper and oxygen are both elements found on the periodic table. They have the following symbols;
Copper = Cu
Oxygen = O
From the given choices, only option 1 has the symbol Cu and O.
So only malachite contains both copper and oxygen.
which statement is correct for all elements in the same group
They have the same number of electrons in the highest occupied energy level
They have the same chemical reactivity
They have the same number of occupied energy levels
They have the same number of neutrons
Shabnam put something in a vessel of water and heated it on a gas stove for 30 minutes. That thing looked the SAME even after 30 minutes of heating. What could she have put into the vessel? A) a steel spoon B) a wax candle C) a handful of sugar D) a piece of chocolate
Answer: She could have put a steel spoon into the vessel. The correct option is A.
Explanation:
When a candle wax is passed through heat, it is capable of melting within 10- 15 minutes of boiling. Therefore it is not capable of looking the same after 30 mins of heating.
When sugar is put into water it dissolves. When heated it has the ability to crystallize out after water is evaporated but doesn't retain its shape.
A piece of chocolate will melt the instance it comes in contact with any form of heat.
A steel spoon is an alloy metal which is not capable of melting by boiling in water for just 30 minutes. A steel is an alloy of Iron and carbon which melts when superheated at the temperature of 1510 degrees.
When heated, calcium carbonate decomposes according to the equation given below:
CaCO3 --> CaO + CO2
If 3.0 moles of CaCO3 are decomposed, how many grams of CO2 will be produced?
44.0 g
88.0 g
132 g
3.00 g
Answer:
132g
Explanation:
The reaction equation is given as:
CaCO₃ → CaO + CO₂
Given;
Number of moles of CaCO₃ = 3 moles
Unknown:
Mass of CO₂ produced = ?
Solution:
From the balanced reaction equation;
1 mole of CaCO₃ will produce 1 mole of CO₂;
3 mole of CaCO₃ will then produce 3 moles of CO₂
To find the mass of CO₂;
Mass of CO₂ = number of moles x molar mass
Molar mass of CO₂ = 12 + 2(16) = 44g/mol
Mass of CO₂ = 3 x 44 = 132g
A man was 200 meter away from work if it took him 133 seconds to get to work
What was his speed?
HELP MEHHHHH
6. Which specific processes in the rock cycle occur beneath the Earth's surface?
Support your answer.
Answer:
Under the earth's surface, rocks melt, metamorphize, and crystalize.
Explanation:
Metamorphic and Igneous rocks are basically dependant on the heat/pressure of the environment under the surface :) Melting, metamorphosing and crystallization all occur under earth's surface.
The specific processes in the rock cycle that occur beneath the Earth surface are :
Melting crystallizationmetamorphizationUnder the Earth surface the specific rock cycle processes that leads to the formation of the different types of rocks includes; Melting, metamorphization and rock crystallization.
Metamorphic rocks are formed from other rocks ( sedimentary and igneous rocks) due to the change in temperature and this process is metamorphization. while igneous rocks are formed from molten rocks caused by the melting process. Sedimentary rocks are formed by the deposition of sediments from weathering of existing rocks this is the crystallization process.
Hence the specific process in the rock cycle that occur beneath the Earth's surface are : Melting, metamorphosing and crystallization.
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Examine the diagram of a cell.
Which organelle is marked with an X?
lysosome
nucleus
chloroplast
vacuole
Answer:
chloroplast
Explanation:
i took the test
How many neutrons does Ruthenium have?
Answer: 57 neutrons
Explanation: Ruthenium has an atomic number of 44, meaning it has 44 electrons, 44 protons, and 57 neutrons.
Answer:
57 neutrons
Explanation:
Ruthenium has atomic number of 44, that is, it contains 44 electrons distributed in atomic orbitals and its nucleus has 44 protons and 57 neutrons (Figure 1). Electron distribution in atomic or molecular orbitals is called electron configuration which for Ru and the other group 8 chemical elements is shown in Table 1.
The average monthly temperatures for January, April, July, and October in Baltimore, Maryland are graphed below. These averages were calculated from 30 years of data.
Nina predicts that the average temperature in Baltimore will be 68°F next April. Why is her prediction probably wrong?
A.
because the average July temperature is greater than 75°F
B.
because 68°F is much lower than the average April temperature
C.
because 53°F is much lower than the average April temperature
D.
because 68°F is much higher than the average April temperature
Answer:the answer is d
Explanation:because the graph shows that that the average temperature is 53 so it only makes sense that the answer is (D)
True or False: The solute is ALWAYS a solid and the solvent is ALWAYS a liquid
Answer:
false
Explanation:
Note that the solvent is the substance that is present in the greatest amount. Many different kinds of solutions exist. For example, a solute can be a gas, a liquid or a solid. ... Note that in each case, the solute particles are uniformly distributed among the solvent particles.
in what aspects is a metalliod similar to metals and similar to non metals
Answer:
Explanation:Metalloids may act either like metals or nonmetals in chemical reactions. Most metalloids have some physical properties of metals and some physical properties of nonmetals. They fall between metals and nonmetals in their ability to conduct heat and electricity. They are shiny like metals but brittle like nonmetals.
Antioxidants are
oxidizing agents found in foods.
reducing agents found in foods.
fat-soluble.
water soluble.
what is Very small and located on ER or located
floating on its own in the cytoplasm, it is
responsible for making proteins for repair and
growth.
What can be represented on paper or computer by using the Lewis Dot structure?
A. the electrons orbital
B. the position of an element in the periodic table
C. the valence electron shells of atoms
D. the number of total electrons
Answer:
option C is correct
Explanation:
Shameeka is studying for an exam. She took the notes below about calcium and chlorine, which are known to form ionic bonds. Calcium, which is a metal, donates 2 electrons to chlorine. The individual calcium atoms become ions with a negative 2 charge. The bond between calcium and chlorine makes the atoms stable. Calcium and chlorine attract each other. Which best describes Shameeka’s error? ive got 2 hours so you dont need to rush
Answer:
Calcium has a charge of positive 2 not negative
Explanation:
Help me plzz I don’t get this question
Answer: this ones old do you still need help on this one?
Explanation:
Through which of the following loose soil materials does water infiltrate fastest?
A. pebbles
B. sand
C. silt
D. clay
Explanation:
I think pebbles because the pebbles can be different sizes and have bigger gaps in between them so the water will go through quicker.
hope this helps srry if wrong
PLS HURRYY ILL NAME YOU BRAINLIESTTT
explain the difference between a compound and a mixture
Answer:Compound: A substance that is made up of more than one type of atom bonded together. Mixture: A combination of two or more elements or compounds that have not reacted to bond together; each part in the mixture retains its own properties. Compound are substances which can be formed by chemically combining two or more elements. Mixtures are substances that are formed by physically mixing two or more substances. Compounds can be of three types, which are: covalent compounds, metallic compounds and ionic compounds.
what color does red represent in the periodic table
Answer:
Gas
Explanation:
Legend primordial element element by radioactive decay Atomic number color: red=gas
You are required to make 250 cm3 of a solution of
sodium hydroxide which has a concentration of
0.1 mol dm-3. What mass of sodium hydroxide would
you need to weigh out?
A 0.1 g
B 1.0 g
C 4.0 g
D 25.0 g
Answer:
b) 1.0g
Explanation:
C=m
MV
where Cis concentration
m is mass of substance
M is molar mass
V is volume of substance
To find m
CMV=m
but M = 23+16+1
= 40
0.1×40×0.25=m
1.0=m
ILL GIVE BRAINLIST Mrs. Kucalaba downloaded some science music from the Internet onto her iPhone. She listened to the science music while she was building a deck in her mom’s yard.
Which energy transformation explains how Mrs. Kucalaba was able to listen to music on her iPhone while building a deck in her mom’s yard?
Question 19 options:
Light energy was transformed to chemical energy
Chemical energy was transformed to sound energy
Sound energy was transformed to chemical energy
Chemical energy was transformed to heat energy
plz help me its the last question
If an atom of Thulium, Tm, has a mass of 172 and ejects an alpha particle, what is the new mass and atomic number? What element does this atom belong to now?
Answer:
¹⁶⁸₇₉Au
Explanation:
The symbol of the atom is given as;
¹⁷²₈₁Tl
If undergoes a nuclear reaction and it ejects an alpha particle;
An alpha particle is the same as an helium atom
¹⁷²₈₁Tl → ₂⁴H + ₐᵇK
K is the hypothetical symbol of the new atom
b is the new mass number
a is the new atomic number;
Conserving mass number;
172 = 4 + b
b = 172 - 4 = 168
Conserving atomic number;
81 = 2 + a
81 - 2 = a
a = 79
The new compound is gold with a symbol of;
¹⁶⁸₇₉Au
What is the mass of 2.1 moles of Ca(OH)2?
The acceleration due to gravity on Earth’s moon is about 1.6m/s2. An astronaut with full survival pack has a mass of 100kg. He lifts a large boulder (rock) having a mass of 50kg. Losing his balance, and letting go of the boulder, the explorer trips and falls off a ledge that is 2m above the moon’s surface. Assuming that both the astronaut and the rock are the same distance from the surface of the moon, which object will hit the ground first:the astronaut or the rock? Explain your answer.
Answer:
Astronaut
Explanation:
Astronaut.He is 100kgs
Earth's land areas, oceans and atmosphere maintain fairly constant average temperatures. What is the best explanation for these constant average temperatures? (8.10 A) Earth's Northern and Southern hemispheres have opposite seasons. Earth's Northern and Southern hemispheres have opposite seasons. Earth is tilted and rotates daily on its axis. Earth is tilted and rotates daily on its axis. The continuous motion of air and water distributes the sun's energy. The continuous motion of air and water distributes the sun's energy. Global weather systems generally move from west to east.
Answer:
The continuous motion of air and water distributes the sun's energy.
Explanation:
The continuous motion air and water helps to distribute the sun's energy throughout the earth, and thus maintain fairly constant average temperatures.
The equatorial regions of the earth receives more heat than regions of higher latitudes. By means of convection air currents, whereby hotter and lighter air from the equatorial regions is circulated for colder and denser air from the regions of higher latitudes, heat is distributed between these regions.
Also, the heat of surface waters at the equatorial regions is circulated in convection currents as seas and oceans move around, to other regions of the earth in order to maintain a fairly constant average temperature.
Answer:
the continuous motion of air and water distributes the suns energy.
Explanation:
How many total atoms found in 2AClCl3
Answer: 4 atoms.
Explanation:
If an atom gains one electron, what charge will it have?
Answer:
It becomes negatively charged
Proton is positive, electron is negative and neutron is neutral
Explanation:
Answer:
If an atom gains one electron, it will have a negative one charge, or -1.
Electrons = Negative
Protons = Positive
Can somebody please help with this question?
How do the scientist know that cells exist