Answer:
2,3,5
Explanation:
Which statements about exothermic and endothermic reactions are correct? (its a multiple choice question)
1 During an exothermic reaction, heat is given out.
2 The temperature of an endothermic reaction goes up because heat is taken in.
3 Burning methane in the air is an exothermic reaction.
A) 1.2 and 3
B) 1 and 2 only
C) 1 and 3 only
D) 2 and 3 only
Answer:
C)1 and 3 only☺️
Explanation:
Which phrase is not an example of intercellular communication?
A chemical messengers dock onto receptors of adrenal gland
B chemical signal from pituitary gland to adrenal gland
C electrical signals pass between heart cells
D a vesicle encloses over a nutrient molecule
Answer: The answer is D
Explanation: I took the quiz just now and got it right
The correct answer is:
D.(a vesicle encloses over a nutrient molecule)
I took the test, hope this helps!
A solution that holds more solute than it normally can under the conditions at a given temperature is _____. supersaturated unsaturated saturated diluted
Answer:
Supersaturated !
Explanation:
How many elements are in H2CrO4
Answer:
3 elements
Explanation:
The elements are:
- Chromium
- Hydrogen
- Oxygen
which statement differentiates between prokaryotic cells and eukaryotic cells?
A.Eukaryotic cells have DNA: prokaryotic cells do not.
B. Prokaryotic cells have DNA: eukaryotic cells do not.
C. Eukaryotic cells have nuclei: prokaryotic cells do not.
D. Prokaryotic cells have nuclei: eukaryotic cells do not.
Answer:
It is C
Explanation:
It is because Prokaryotic cells mostly don't have a nucleus.
Answer:
It is C.Eukaryotic cells have nuclei; prokaryotic cells do not
Explanation:
I just watched a video of it.
how many moles in 1.505x10^23 Na atoms
Answer:
The answer is 0.25 molesExplanation:
To find the number of moles in a substance given it's number of entities we use the formula
[tex]n = \frac{N}{L} \\[/tex]
where n is the number of moles
N is the number of entities
L is the Avogadro's constant which is
6.02 × 10²³ entities
From the question
N = 1.505 × 10²³ Na atoms
We have
[tex]n = \frac{1.505 \times {10}^{23} }{6.02 \times {10}^{23} } = \frac{1}{4} \\ [/tex]
We have the final answer as
0.25 molesHope this helps you
based on the half-life of Tc-99, how many half-lives have to pass for a 150 mg sample of Tc-99 to decay down to 30mg?
Answer:
2.322 half-lives have passed to decay down from 150 miligrams to 30 miligrams.
Explanation:
The half of Technetium-99 is approximately 211000 years. The decay of isotopes is represented by the following ordinary differential equation:
[tex]\frac{dm}{dt} = -\frac{m}{\tau}[/tex] (Eq. 1)
Where:
[tex]\frac{dm}{dt}[/tex] - First derivative of isotope mass in time, measured in miligrams per year.
[tex]m[/tex] - Mass of the isotope, measured in miligrams.
[tex]\tau[/tex] - Time constant, measured in years.
Now we proceed to obtain the solution of this differential equation:
[tex]\frac{dm}{m} = -\frac{dt}{\tau}[/tex]
[tex]\int {\frac{dm}{m} } = -\frac{1}{\tau}\int dt[/tex]
[tex]\ln m = -\frac{t}{\tau}+C[/tex]
[tex]m(t) = m_{o}\cdot e^{-\frac{t}{\tau} }[/tex] (Eq. 2)
Where:
[tex]m_{o}[/tex] - Initial mass of the isotope, measured in miligrams.
[tex]t[/tex] - Time, measured in years.
The time passed for isotope is cleared within the equation described above:
[tex]\ln \frac{m}{m_{o}} = -\frac{t}{\tau}[/tex]
[tex]t = -\tau \cdot \ln \frac{m}{m_{o}}[/tex]
In addition, we can obtain the time constant as a function of half-life:
[tex]\tau = \frac{t_{1/2}}{\ln 2}[/tex] (Eq. 3)
If we know that [tex]t_{1/2} = 211000\,yr[/tex], [tex]m_{o} = 150\,mg[/tex] and [tex]m = 30\,mg[/tex], then the time passed is:
[tex]\tau = \frac{211000\,yr}{\ln 2}[/tex]
[tex]\tau \approx 304408.654\,yr[/tex]
[tex]t = -(304408.654\,yr)\cdot \ln \left(\frac{30\,mg}{150\,mg} \right)[/tex]
[tex]t \approx 489926.829\,yr[/tex]
The amount of passed half-lives is that time divided by a half-life. That is:
[tex]n = \frac{489926.829\,yr}{211000\,yr}[/tex]
[tex]n = 2.322[/tex]
2.322 half-lives have passed to decay down from 150 miligrams to 30 miligrams.
The thermite reaction occurs when iron(III) oxide reacts with solid
aluminum. The reaction is so hot that molten iron forms as a product.
>
Fe2O3(s) + Al(s) → Fe(C) + Al2O3(s)
What mass of aluminum should be used in order to completely
consume 10.0 g Fe2O3(s)? If the reaction described produces 5.3 g
Al2O3(s), what is the percent yield?
Answer:
[tex]m_{Al}=3.38gAl[/tex]
[tex]Y=83.1\%[/tex]
Explanation:
Hello.
In this case, for the given balanced reaction:
[tex]Fe_2O_3(s) + 2Al(s)\rightarrow 2Fe(s) + Al_2O_3(s)[/tex]
For 10.0 g of iron (III) oxide (molar mass = 160 g/mol), based on the 1:2 mole ratio with Al (atomic mass = 27 g/mol), the required mass is then:
[tex]m_{Al}=10.0gFe_2O_3*\frac{1molFe_2O_3}{160gFe_2O_3} *\frac{2molAl}{1molFe_2O_3} *\frac{27gAl}{1molAl} \\\\m_{Al}=3.38gAl[/tex]
Moreover, as 5.3 g of aluminum oxide are actually yielded, from the 10.0 g of iron (III) oxide, we can compute the theoretical mass of aluminum oxide (molar mass = 102 g/mol) via their 1:1 mole ratio:
[tex]m_{Al_2O_3}=10.0gFe_2O_3*\frac{1molFe_2O_3}{160gFe_2O_3} *\frac{1molAl_2O_3}{1molFe_2O_3} *\frac{102gAl_2O_3}{1molAl_2O_3} \\\\m_{Al_2O_3}=6.38gAl_2O_3[/tex]
Thus, the percent yield (actual/theoretical*100%) turns out:
[tex]Y=\frac{5.3 g}{6.38 g}* 100\%\\\\Y=83.1\%[/tex]
Best regards.
What is conduction?
Transfer of heat through circular movement
Transfer of heat through direct physical contact
Transfer of heat through electromagnetic waves
Transfer of heat through the movement of part
Answer:
Transfer of heat through direct physical contact
Explanation:
The meaning of conduction is the transfer of heat directly transmitted through a substance when there is the difference between temperature and electrical potential. Hope it helps!
Answer:
B
Explanation:
A piece of metal is composed of atoms. Each atom in the metal contains 29 protons. How is the metal classified?
Answer:
The metal is Copper
Explanation:
Matter is composed of atoms, which is the smallest indivisible particle of an element. The atom of an element consists of three subatomic particles namely: proton, electron and neutron etc.
The proton, which is the positively charged particle, is equal to the electron, which is the negatively charged particle. The proton number of the atom is the ATOMIC NUMBER of an element.
In the periodic table, the element with atomic number 29, which also means proton number 29 is Copper (Cu).
What is the same on the left and right side of a balanced equation? Explain your answer.
Answer:
Number of atoms of elements are same on left and right side of balance equation.
Explanation:
Every chemical reaction must follow the law of conservation of mass. According to which mass can neither be created nor destroy but it change from one to another form. It means mass remain conserved. That is why we need to balance the chemical equation because mass remain same on both side of equation. Consider the example,
Chemical equation:
N₂ + H₂ → NH₃
We can see that nitrogen and hydrogen react with each other and from ammonia. We need to balance the equation to have equal amount on both side.
Balance chemical equation:
N₂ + 3H₂ → 2NH₃
It means mass remain same but change from one to another form.
A balanced equation is one that is having a chemical reaction where the numbers of atoms. Here the number of elements in each reaction and the total charges are the same. This includes both the reactant and the product.
However, the mass and charge are balanced on both sides of the reaction. Hence the left and the right side is always equal to the number of atoms. Thus the chemical reaction is a balance of atoms involved in the reaction.Learn more about the same on the left and right sides of a balanced equation.
brainly.ph/question/20750343.
How would I create a Lewis dot structure with the compound: CHBr2Cl
Answer:
Step 1: Find the Total Number of Valence Electrons. ...
Step 2: Find the Number of Electrons Needed to Make the Atoms "Happy" ...
Step 3: Determine the Number of Bonds in the Molecule. ...
Step 4: Choose a Central Atom. ...
Step 5: Draw a Skeletal Structure. ...
Step 6: Place Electrons Around Outside Ato
Explanation:
When iron reacts with oxygen, it forms iron oxide, or rust.
4 Fe + 3 O2 2 Fe2O3
If 112 g of iron (Fe) combines with 24 g of oxygen (O2), how much iron oxide is formed?
Answer:
Mass of iron oxide: 79.85 g
Explanation:
Given data:
Mass of iron = 112 g
Mass of O₂ = 24 g
Mass of iron oxide formed = ?
Solution:
4Fe + 3O₂ → 2Fe₂O₃
Number of moles of Fe:
Number of moles = mass/ molar mass
Number of moles = 112 g/ 55.85 g/mol
Number of moles = 2 mol
Number of moles of O₂:
Number of moles = mass/ molar mass
Number of moles = 24 g/ 32 g/mol
Number of moles = 0.75 mol
Now we will compare the moles of oxygen and iron with iron oxide.
Fe : Fe₂O₃
4 : 2
2 : 2/4×2 = 1
O₂ : Fe₂O₃
3 : 2
0.75 : 2/3×0.75 = 0.5
The number of moles of iron oxide formed by oxygen are less thus it will be limiting reactant.
Mass of iron oxide:
Mass = number of moles × molar mass
Mass = 0.5 mol × 159.69 g/mol
Mass = 79.85 g
Answer:
136 g Fe2O3
Explanation:
study island
18. Which of these is an ion?
A. Fluorine with 9 protons
B. Calcium with 18 electrons
C. Calcium with 18 neutrons
D. Fluorine with 9 neutrons
An object with a mass of 15 kg has an acceleration of 3 m/s/s. What is the force
applied to the object? *
45 N
5N
18 N
Answer:
45N
Explanation:
force=mass×acceleration
Nervous tissue transmits messages throughout the human body by
contracting.
providing protection.
conducting impulses.
absorbing vital nutrients.
Answer: conducting impulses
Explanation:
just did it on edge
Answer:
c. conducting impulses.
Explanation:
got it right on edg, hope this helps!
HEEELLLPPPP:(!!!!! im stuckkkk!!!
Answer:
LIGHT
AIR
SHELTER
FOOD
WATER
Answer:
light
air
shelter
food
water
Calculate the atomic mass of the unknown element X described below.
Please help
Answer:
286
Explanation:
Add atomic mass of all the Isotopes,
Outcome = 825
divide it by number of isotopes which is 4 because there are 4 isotopes
Atomic mass of x = [tex]\frac{825}{4}[/tex]
Atomic mass of x is 286
The atomic mass of the unknown element X is 206 amu. Thus option B is correct.
What is atomic mass?Atomic mass is defined as the relative mass of the element's atom in comparison to the mass of an atom of the C12 isotope.
In an example, the general atomic mass is the average of the atomic masses of a large number of different isotopes.
First we added atomic mass of each isotopes
= 204 + 206 + 207 + 208 = 824
Now to calculate the atomic mass of element X we divide it by 4 as there is four isotopes
So, atomic mass = 824 / 4
= 206 amu
Thus, the atomic mass of the unknown element X is 206 amu. Thus option B is correct.
To learn more about atomic mass, refer to the link below:
https://brainly.com/question/17067547
#SPJ5
What do we call the study of matter and how matter changes?
Answer:
Explanation:
Chemistry is the study of matter and the changes that matter undergoes. Matter is anything that has mass and takes up space.
Help me lol
I’ll give branliest if two people answer
Answer:
I think all of the above
Explanation:
Put as brainliest if you wish
PLS HELP ITS URGENT
Some plant cells need energy to carry nutrients across the cell membrane. Which type of energy transformation does these plant cells use to bring the nutrient molecule inside the cell membrane?
thermal energy to kinetic energy
potential energy to light energy
chemical energy to kinetic energy
kinetic energy to potential energy
Answer:
Answer
The answer is option 4
The energy transformation during nutrients transportation across the cell membrane is transformation from chemical energy to kinetic energy, where the uphill and downhill movements of molecules based on concentration gradient carries the whole process.
What is energy transformation?The total energy in a system is always conserved. However, one form of energy can be transformed into another form. For example we uses electrical devices such as bulbs fan etc, wherever the energy transformation is getting way from electrical energy to light or mechanical energy.
In plant cells nutrient molecules and ions are balanced inside and outside the cell and hence they are transported across the cell membrane by a concentration gradient with a chemical energy produced by the molecules.
The chemical energy inside of the ions and molecules converts to kinetic energy to transport itself through downhill and uphill mechanisms with aid of various enzymes and electron channels.
To find more on energy transformation, refer here:
https://brainly.com/question/29102331
#SPJ6
What is epithelial tissue characterized by?
closely packed cells
sarcomeres
many cell junctions
an extracellular matrix
Answer:
closely packed cells
many cell junctions
Explanation:
Answer:
A,B
Explanation:
EDGE2021
What was the average speed of the truck for this trip?
compare and contrast solids liquids and gases in terms of volume shape compessibility and energy
Answer:
solid has definite shape and volume.
liquid do not have definite shape but have definite volume.
gas do not have definite shape and definite volume.
solid have lowest compressibility out of three, liquid have more compressibility than solid but less than gases. gases have the highest compressibility out of three. Molecules in the solid phase have the least amount of energy, while gas particles have the greatest amount of energy. The temperature of a substance is a measure of the average kinetic energy of the particles.
How many total atoms are in 0.550 g of P2O5?
Answer:
Total atoms in 0.550g of =1.631x1022
Explanation:
answer is above
an atom has 79 protons, 78 electrons and a mass number of 118. how many neutrons does this atom have
Answer:
39
Explanation:
Electrons weigh almost nothing, so their mass doesn't really matter for these types of problems. Just subtract 118-79 to find the remaining mass which is for the neutrons.
Mass can be changed into energy in a ____ reaction
A)Chemical
B)Nuclear
what is the chemical formula for the magnesium ion and the carbonate ion?
Answer: The formula for magnesium carbonate is MgCO_3.
Explanation:
Convert 5.4g of NaCl to moles
Answer:
.0924 moles of NaCl
Explanation:
So you know you have 5.4 g of NaCl and you need to know how many moles there are in this amount of NaCl
You'll need to find the atomic mass of the compound NaCl to help you solve for moles Sodium (Na) on the periodic table has a mass of 22.99 Chlorine (Cl) on the periodic table has a mass of 35.45Add these two together----> 22.99 + 35.45 = 58.44
Now you can calculate for moles
Written-out method:
5.4 grams of NaCl | 1 mole of NaCl
| 58.44 grams NaCl = .0924 moles of NaCl
Plug into calculator method:
(5.4 g of NaCl/ 58.44g NaCl= .0925 moles)
2. How does friction effect speed?
Answer:
It acts as a force upon it like in newtons first law of motion an object in motion will stay in motion until a force acts upon it So friction bascicallly slows it down or stops it completly
Explanation: