In toxicology, the median lethal dose, LD₅₀, LC₅₀ or LCt₅₀ is a measure of the lethal dose of a toxin, radiation, or pathogen. The value of LD₅₀ for a substance is the dose required to kill half the members of a tested population after a specified test duration.
Which is a definite sign of a chemical reaction?
Chemical properties change.
Physical properties change.
A gas forms.
A solid forms
Answer: here i am choosing two answer because i am not sure . a gas forms and a solid forms
Explanation: a solid forms thus is to say a precipitate is formed
a gas forms thus to say effervescence , fizzing and bubbling whiles a gas is being produced.
How much Pb(NO3)2 would need to be added to 100 mL of water to make a saturated solution at 40°C.
Answer:
70g of Pb(NO3)2 would need to be added
Explanation:
As you can see in the solubility graph of lead nitrate, Pb(NO₃)₂, the solubility of this salt (That is, the maximum amount of the salt that can be dissolved in 100g of the solvent producing a homogeneous solution) is 70g in 100g of water = 70g of the salt in 100mL of water.
A saturated solution is also defined as solubility: The maximum amount of a solute that can be dissolved in a solvent.
That means:
70g of Pb(NO3)2 would need to be added
What is natural gas and how does it work
Answer:
Natural Gas is a fossil energy source that formed deep beneath the Earth's surface. It is used in power plants to generate electricity by burning natural gas as their fuel.
Explanation: I hope this helped :)
Answer:
A molecule of natural gas is made up of carbon and hydrogen. When the hydrogen is segregated from the carbon and filled into a fuel cell, it fuses with oxygen to produce water, electricity, and heat. The carbon is released as carbon dioxide in smaller quantities than from gas turbines.
Explanation:
This is the site I got the info from :
How Natural Gas Works | Peak Oilhttps://www.peakoil.net › non-renewable › how-natural-g
12. A. 2 g of ferrous sulphate crystals 5 points
are heated in a dry boiling tube. a)
Name and define the type of reaction
that has taken place. b) Write
balanced chemical equation for the
above reaction. c) List two main
observations of this reaction. B. A
shining metal 'M'on burning gives a
dazzling white flame and changes to
a white powder ‘N’. a) Identify ‘M'and
'N'. b) Name the type of reaction
taking place and write the balanced
chemical equation.
Answer:
A) Decomposition reaction.
Decomposition reaction is defined as a chemical reaction whereby a compound is broken down into 2 or more simpler substances.
B) 2FeSO4 + Heat > Fe2O3 + SO2 + SO3
C) - Gas evolution because a gas is part of the product
- Upon heating its colour gradually changes from pale green to reddish brown which implies a change in state
Explanation:
A) Name of the reaction is; Decomposition reaction.
Decomposition reaction is defined as a chemical reaction whereby a compound is broken down into 2 or more simpler substances.
B) The balanced chemical equation is;
2FeSO4 + Heat > Fe2O3 + SO2 + SO3
C) From experience, the 2 main observations of this reaction are;
- Gas evolution because a gas is part of the product
- Upon heating its colour gradually changes from pale green to reddish brown which implies a change in state.
100 POINTS!!! AND BRAINLIEST!!!
This tree species was preserved as a fossil in the Arizona desert. The species is now extinct. Describe what the environment was like when the tree lived and how it is different now. Then, infer why this type of tree and other living things that lived with it are extinct.
An atom of element X has an atomic number of 11 and a mass number of 23. .
a) What is the definition of atomic number?
b) How many protons, electrons and neutrons are in this atom?
c) A different atom of X has an atomic number of 11, but a mass number of 24. Give a
name for these two forms of X.
d) Would these two atoms have similar chemical properties? Give a reason for your
answer.
Answer:
ssaasasasassdsdsdafdftrga*b*y/a la 3
Explanation:
Answer:
a) the number of protons in an atom
b) 11 protons, 11 electrons and 12 neutrons.
c) Isotope
d) yes, they still have the same number of protons and electrons.
Explanation:
b) Number of neutrons = mass number - atomic number
Atoms have the same number of electrons and protons
c) isotopes are atoms with the same number of protons but a different number of neutrons.
Hope this helped !
2C2H6 + 7O2 → __CO2 + 6H2O
What coefficient will need to be placed in the blank in order for the following equation to be correctly balanced?
A.
1
B.
3
C.
4
D.
7
Answer:
From the Combustion formula of Organic Compounds....
Exactly 4 Moles of CO2 would make the equation balanced
So
OPTION C
4MOLES
Alguien sabe como puedo saber si la bebida (gaseosa) al contener agua carbonatada, ¿esta pasa por electrolisi?, ya que el H2O, podria ser que puede ser de reaccion de sintesis, que seria H2+02------>H20? Seria hidrogeno gaseoso y pxigeno gaseoso formaria el agua carbonatada?, ayuda tengo esta duda >_
Answer:
Por formación de burbujas.
Explicación:
La presencia de burbujas en la superficie de la bebida ayuda a determinar si la bebida tiene gas carbonatado o dióxido de carbono. El gas de dióxido de carbono no se puede mezclar con agua ni disolver en agua normalmente. Se puede agregar mediante alta presión al agua para que cuando se coloquen en condiciones normales, el dióxido de carbono se libere en forma de burbujas. No, el gas hidrógeno y el gas hidrógeno no podrían formar agua carbonatada porque ambos son átomos diferentes. El agua carbonatada tiene gas dióxido de carbono, no gas hidrógeno.
Please help me. I am doing a test and, I don’t know the answer.
Answer:
it's the third one ozone layer depletion
When 250 ml of water is added to 35 ml of 0.2 M HCl
which of the following best describes the use of a non renewable resource?
Answer:
Non-renewable resources, such as coal and oil, are the primary source of power in the world, and they are used to power vehicles, factories, and homes. Although affordable, they can be harmful to the environment and are one of the notable contributors to global warming.
Explanation:
source:cfi
2
A chart with the densities of four metals is shown.
Metal
Density (gicm')
Titanium
4.5
Zinc
7.1
Nickel
88
Silver
10.5
Students were given a sample of an unknown metal and told to determine
its density. They measured its mass as 26.4 g and its volume as 3.0 cm?
Use the chart to determine which metal the students were given.
Answer:
mass(m)=26.4g
volume (v)=3.0cm²
we have
density =m/v=26.4/3=8.8g/cm³
since it is equal to density of nickel.
Option C nickel is a required answer.
Answer:
[tex]\huge\boxed{\fcolorbox{green}{yellow}{option \: \: c}}[/tex]
You are performing a titration with 0.80 M sodium hydroxide as a standard. Estimate how much would be needed to change 125 mL of a 2.0 M solution of nitric acid to a faint pink endpoint.
Answer:
312.5 mL
Explanation:
We'll begin by writing the balanced equation for the reaction. This is illustrated below:
HNO₃ + NaOH —> NaNO₃ + H₂O
From the balanced equation above,
The mole ratio of acid, HNO₃ (nₐ) = 1
The mole ratio of base, NaOH (n₆) = 1
Finally, we shall determine the volume of the base, NaOH needed for the reaction. This can be obtained as follow:
Molarity of base, NaOH (M₆) = 0.08 M
Volume of acid, HNO₃ (Vₐ) = 125 mL
Molarity of acid, HNO₃ (Mₐ) = 2 M
Volume of base, NaOH (V₆) =?
MₐVₐ / M₆V₆ = nₐ/n₆
2 × 125 / 0.80 × V₆ = 1/1
250 / 0.80 × V₆ = 1
Cross multiply
0.80 × V₆ = 250
Divide both side by 0.8
V₆ = 250 / 0.8
V₆ = 312.5 mL
Thus, the volume of the base, NaOH needed for the reaction is 312.5 mL
A 3.0 g sample of a gas occupies a volume of 1.00L at 100C and 740 torr pressure. The molecular weight of the
(Give the same ANSWER for the next TWO problems)
gas is
Answer:
94.2 g/mol
Explanation:
Ideal Gases Law can useful to solve this
P . V = n . R . T
We need to make some conversions
740 Torr . 1 atm/ 760 Torr = 0.974 atm
100°C + 273 = 373K
Let's replace the values
0.974 atm . 1 L = n . 0.082 L.atm/ mol.K . 373K
n will determine the number of moles
(0.974 atm . 1 L) / (0.082 L.atm/ mol.K . 373K)
n = 0.032 moles
This amount is the weigh for 3 g of gas. How many grams does 1 mol weighs?
Molecular weight → g/mol → 3 g/0.032 moles = 94.2 g/mol
Natalia dipped two feathers in oil. Then she dipped one feather in cold water and the other feather in hot water. She swirled both feathers around for 20 seconds, then removed them. Her results are in the table. Cold Water Hot Water Before Oil After Oil After Water Before Oil After Oil After Water Mass 1.2 g 4.5 g 4.2 g 1.2 g 4.4 g 3.5 g She also took a picture of each feather after swirling it in water. two feathers, each with oil and beads of water Was either the cold water or the hot water able to remove the oil? Explain your reasoning.
Answer:
The hot water was better for removing the oil.
Explanation:
You can see that because the mass went down more with the hot water. So, that means that more oil was taken out of the feather with hot water.
Answer:
The mass changed from 1.1grams to 4.5 grams. The appearance is another thing that changed when it got dipped in oil. The feather look like it lost some feathers or the feathers became transparent. The feather just looks soggy and heavier overall. I believe that if Natalia dips the feather covered in oil in cold water, the feather will remain the same. If she were to dip it in hot water, the feather will get rid of the oil mostly. Think about it, in the ocean the water is cold right? So when oil spills in the ocean it will stay there. Hot water is the best to remove the oil from the feather.
Explanation:
Hopefully this will help.
Which of the following processes is not an example of physical weathering?
A. acidification
B. abrasion
C. frost action
D. exfoliation
Answer:
acidification
Answer:
I think its A
Explanation:
Hope this helps: )
Cu1+ and O2- what is the formula and what is the name of it
Answer:
copper I oxide
Explanation:
Copper is known to form two oxides; copper I oxide and copper II oxide.
In the question we have the ions; Cu1+ and O2-. Ionic compounds are formed by a combination of ions as typified below;
Cu^+ + O^2- -------> Cu2O
This compound is copper I oxide
What is the name of this hydrocarbon?
Answer:
2,3-dimetylpentane
Explanation:
.....................
PLEASE HELP ME If a radioactive substance has an initial mass of 50 grams
and its mass halves every 5 years, what is the number of
grams remaining after 20 years?
Answer: [tex]3.125\ g[/tex]
Explanation:
Given
Initial mass [tex]A_o=50\ g[/tex]
half-life is [tex]T_{\frac{1}{2}}=5\ years[/tex]
At any time the left amount is given by
[tex]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[/tex]
15.True or False:
The concentration of a solution can be increased indefinitely by
adding solute
What is the pH of the solution if the [H3O+] concentration is 2.5 X 10-4 M?
HELP I'M DESPERATE! NO LINK!
Answer:
3.60
Explanation:
To calculate the pH of any solution, use the formula;
pH= -log[ concentration ] and for this case take pH= -log[H3O+]
= -log[2.5x10^-4]
therefore pH= 3.60
The idea of pH mainly applies in the determination of the nature of various solutions to the used in the chemical analysis. The correct pH must be determined in order to get accurate results. Ionic equillibria mostly involves the calculations involving pH which is normally obtained after determination of equilibrium concentrations.
Scientists, emergency personnel, and the weather service keep a close eye on this potential natural disaster that impacts Florida several times each year. What is this disaster being tracked here?
Answer:
hurricane
Explanation:
How would the number of atoms in a 2.02g sample of hydrogen compare to the number of atoms in a 32.00g sample of oxygen
Answer:
Number of atoms is equal.
Explanation:
1 mol of anything contains NA particles.
NA is known as Avogadro's number, 6.02×10²³
We determined the moles of each compound. Both molecules are dyatomic,
H₂ → 2.02 g . 1mol / 2.016 g = 1 mol
O₂ → 32 g . 1mol / 32g = 1 mol
Both have the same amount of moles.
In conclussion, the number of atoms is the same in both samples.
Under Adolf Hitler, Germany violated the Treaty of Versailles by expanding its
military and occupying the Rhineland. How did the League of Nations respond to
these violations?
The League of Nations issued a declaration of war on Germany.
O The League of Nations condemned the violations but took no other action.
O The League of Nations imposed harsh sanctions on Germany.
The League of Nations sent a multinational peacekeeping force to the region.
Answer:
B. The League of Nations condemned the violations but took no other action.
Explanation:
Nazi leader, Adolf Hitler violated the Treaty of Versailles by sending German military forces in Rhineland. He not only violated the Treaty of Versailles but the Locarno Pact also.
The treaty was signed in 1919 to end the war between Germany and the Allied Powers.
Even after Adolf Hitler violated the treaty, the League Nations did not take any actions.
Therefore, option B is correct.
Which is the correct Lewis dot structure of NH2?
H-N-H
H-N-H
A.
B.
N-H-H
H-N-H
C.
D.
-H-N-H
E.
ОА А
ов. В
C C
OD D
ОЕ Е
Answer:
D
Explanation:
positivities and negativity of computer creativity
answerrr BRAINLIEST PLS FAST
Explanation:
Some of the positive effects are faster communication, an organization of data and information, computerization of tasks, and easier access to the information. Some of the negative effects of computers are human's break their social interact with friends and families, cause back problem, depression, and poor health.Answer:
Creativity is a phenomenon whereby something somehow new and somehow valuable is formed. The created item may be intangible (such as an idea, a scientific theory, a musical composition, or a joke) or a physical object (such as an invention, a printed literary work, or a painting).
Scholarly interest in creativity is found in a number of disciplines, primarily psychology, business studies, and cognitive science, but also education, the humanities, technology, engineering, philosophy (particularly philosophy of science), theology, sociology, linguistics, the arts, economics, and mathematics, covering the relations between creativity and general intelligence, personality type, mental and neural processes, mental health, or artificial intelligence; the potential for fostering creativity through education and training; the fostering of creativity for national economic benefit, and the application of creative resources to improve the effectiveness of teaching and learning.

A picture of a lightbulb is associated with someone having an idea, an example of creativity.
what is the molarity of a solution prepared dissolving 317 g of CaCl2 into enough water to make 2.50 L of solution?
Answer:
1.14 M
Explanation:
Step 1: Calculate the moles corresponding to 317 g of calcium chloride (solute)
The molar mass of calcium chloride is 110.98 g/mol.
317 g CaCl₂ × 1 mol CaCl₂/110.98 g CaCl₂ = 2.86 mol CaCl₂
Step 2: Calculate the molarity of the solution
Molarity is equal to the moles of solute divided by the liters of solution.
M = moles of solute / liters of solution
M = 2.86 mol / 2.50 L = 1.14 mol/L = 1.14 M
HELP ASAP 10 POINTSSS
In this diagram, the medium on top is air and the medium on bottom is glass. Which vocab word best describes what is happening when the light wave passes from the air into the glass?
Question 2 options:
resolution
diffraction
refraction
reflection
Answer: refraction
Explanation: this is because during refraction light moves from one medium to another.
How many moles are in a solution with a concentration of 5 M and a volume of 0.25 L?
Answer:
160 mL
Explanation:
.
What primarily causes the spread of acid rain?
through groundwater and aquifers
through streams and rivers
through the atmosphere
through ocean currents
Answer:
(C) through the atmosphere
Explanation: