Chemical Changes
Chemical changes take place at the molecular level. A chemical change produces a new substance. Another way to think of it is that a chemical change accompanies a chemical reaction. Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan, and mixing hydrochloric acid and sodium hydroxide to make salt and water.
Physical Changes
Physical changes are concerned with energy and states of matter. A physical change does not produce a new substance, although the starting and ending materials may look very different from each other. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle.
How to Tell Chemical & Physical Changes Apart
A chemical change makes a substance that wasn't there before. There may be clues that a chemical reaction took places, such as light, heat, color change, gas production, odor, or sound. The starting and ending materials of a physical change are the same, even though they may look different.
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An element has five isotopes. Calculate the atomic mass of this element using the information below. Show all your work. Using the periodic table, identify the element this is likely to be and explain your choice. (18 pts)
A) Isotope 1 – mass: 64 amu; percent abundance: 48.89%
B) Isotope 2 – mass: 66 amu; percent abundance: 27.81%
C) Isotope 3 – mass: 67 amu; percent abundance: 4.11%
D) Isotope 4 – mass: 68 amu; percent abundance: 18.57%
E) Isotope 5 – mass: 70 amu; percent abundance: 0.62%
Answer: Sol:-
Data provided in the question is :-
Atomic mass of isotope -1 = 64 amu
Atomic mass of isotope -2 = 66 amu
Atomic mass of isotope -3 = 67 amu
Atomic mass of isotope -4 = 68 amu
Atomic mass of isotope - 5 = 70 amu
Percentage abundace of isotope - 1 = 48.89 %
Percentage abundance of isotope -2 = 27.81 %
Percentage abundance of isotope - 3 = 4.11%
Percentage abundance of isotope-4 = 18.57%
Percentage abundance of isotope - 5 = 0.62 %
Formula used :-
Average atomic mass of an element =[ {(atomic mass of isotope-1 * percentage abundance of isotope-1) + ( atomic mass of isotope-2 * percentage abundance of isotope -2) + ( atomic mass of isotope -3 * percantege abundance of isotope-3 ) + ( atomic mass of isotope-4 * percentage abundance of isotope-4) + (atomic mass of isotope-5 * percentage abundance of isotope-5)} / 100]
Calculation :-
Put all the value in the formula :-
Average atomic mass of an element = [{(64 * 48.89) + (66 * 27.81) + (67 * 4.11) + (68 * 18.57) + (70 * 0.62)} / 100] amu
= [{(3128.96) + (1835.46) +(257.37) + (1262.76) + (43.4)} / 100] amu
= {(6528.04) / 100} amu
= 65.2804 amu
Average atomic mass of an element is = 65.2804 amu
Then this mass is approximatly equal to atomic mass of zinc so this element would be zinc
atomic mass of zinc = 65.38 \approx 65.2804 amu
The 10x SDS gel electrophoresis buffer contains 250mM Tris HCl, 1.92M Glycine, and 1% (w/v) SDS. Buffers are always used at 1x concentration in the lab (unless specified otherwise in the protocol), so you will have to dilute the 10x buffer to 1x before use. What is the concentration of Tris and SDS in the 1x buffer
Answer:
25 mM Tris HCl and 0.1% w/v SDS
Explanation:
A 10X solution is ten times more concentrated than a 1X solution. The stock solution is generally more concentrated (10X) and for its use, a dilution is required. Thus, to prepare a buffer 1X from a 10X buffer, you have to perform a dilution in a factor of 10 (1 volume of 10X solution is taken and mixed with 9 volumes of water). In consequence, all the concentrations of the components are diluted 10 times. To calculate the final concentration of each component in the 1X solution, we simply divide the concentration into 10:
(250 mM Tris HCl)/10 = 25 mM Tris HCl
(1.92 M glycine)/10 = 0.192 M glycine
(1% w/v SDS)/10 = 0.1% w/v SDS
Therefore the final concentrations of Tris and SDS are 25 mM and 0.1% w/v, respectively.
which section from the article most emphasizes the role of technological development in the discovery of cells
Answer:
B. The microscope paved the way
Explanation:
This section from the article, "History of the Cell: Discovering the Cell", that emphasizes the role of technological development in the discovery of cells, is the subheading, "The microscope paved the way". In this subheading, the author narrated how Robert Hooke improved the existing microscope, and was able to discover the cell through it.
Further improvement of the simple microscope by Antonie van Leeuwenhoek led to the discovery of bacteria and protozoa.
What is the difference between stored energy and usable energy
answer:
In biology, the energy that is stored in the bonds between compounds is termed as the chemical energy. This chemical energy is released and converted into different forms according to the functions of the body.
Potential energy can be described as the energy that is stored in an object. In physics, the energy that an object possesses while at rest is termed as the potential energy.
The energy that can be used during work is termed as the kinetic energy. In physics, kinetic energy can be described as the energy that an object possesses while in motion.
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Answer: The stored energy is termed as potential energy while the working energy is termed as kinetic energy. The electricity used in our homes is also a form of energy because it is a form of usable power. The places from which the different energies are obtained are known as energy sources.
7. Use the concepts of relative abundance and relative weight to explain why carbon has an atomic mass of 12.011 amu when there are three isotopes of carbon weighing 12 amu, 13 amu and 14 amu. Why is the atomic mass not 13?
The uncertainties of the delta measurements and the uncertainty of the atomic weight derivedfrom the best measurement of isotopic abundances constrain the number of significant figures in theatomic-weight values of the upper and lower bounds. For carbon, the fifth digit after the decimal pointis uncertain because of the uncertainty value of 0.000 027. Therefore, the number of significant digitsin the atomic-weight value is reduced to four figures after the decimal point. The Commission may rec-ommend additional conservatism and reduce the number of significant figures further. For the lowerbound of carbon, 12.009 635 is truncated to 12.0096. For an upper bound, the trailing digit is increasedto ensure the atomic-weight interval encompasses the atomic-weight values of all normal materials. Inthe case of carbon, the upper bound is adjusted from 12.011 532 to 12.0116 to express four digits afterthe decimal point. The lower and upper bounds are evaluated so that the number of significant digits ineach is identical. If a value ends with a zero, it may need to be included in the value to express therequired number of digits. The following are examples of lower and upper atomic-weight bounds foroxygen that could be published by the Commission in its various tables.
---------------------------
Extracted from" Atomic weights of the elements 2009 (IUPAC Technical Report)"
How much heat must be used to raise the
temperature of 180. g water from 19° C to 96°C?
The specific heat of water is 4.18 J/gºC.
Answer:
Q = 57934.8 J
Explanation:
Given data:
Mass of water = 180.0 g
Initial temperature = 19°C
Fina temperature = 96°C
Specific heat capacity of water = 4.18 J/g.°C
Heat absorbed = ?
Solution:
Formula:
Q = m.c. ΔT
Q = amount of heat absorbed or released
m = mass of given substance
c = specific heat capacity of substance
ΔT = change in temperature
ΔT = 96°C - 19°C
ΔT = 77°C
Q = 180.0 g×4.18 J/g.°C×77°C
Q = 57934.8 J
When Elsa freezes things, is it an example of an exothermic or
endothermic reaction? Explain.
Answer:
endothermic reaction
Explanation:
When Elsa from Frozen freezes things, it is an example of an endothermic chemical reaction.
An endothermic involves a reaction in which heat is absorbed from the surrounding. Hence the surrounding becomes colder at the end of the the change.
So, Elsa draws heat from the environment and this causes the environment to be colder and things that are in contact with her.
The camel stores the fat tristearin (C57H110O6) in its hump. As well as being a source of energy, the fat is also a source of water because, when it is used, the reaction 2 C57H110O6(g) + 163 O2(g) 114 CO2(g) + 110 H2O(ℓ) takes place. What mass of water is available from 1.6 pound of this fat? Answer in units of g.
Answer:
8.1 × 10² g
Explanation:
Step 1: Write the balanced equation
2 C₅₇H₁₁₀O₆ + 163 O₂ ⇒ 114 CO₂ + 110 H₂O
Step 2: Convert 1.6 lb of C₅₇H₁₁₀O₆ to g
We will use the conversion factor 1 lb = 453.592 g.
1.6 lb × 453.592 g/1 lb = 7.3 × 10² g
Step 3: Calculate the moles corresponding to 7.3 × 10² g of C₅₇H₁₁₀O₆
The molar mass of C₅₇H₁₁₀O₆ is 890.83 g/mol.
7.3 × 10² g × 1 mol/890.83 g = 0.82 mol
Step 4: Calculate the moles of water produced from 0.82 moles of C₅₇H₁₁₀O₆
The molar ratio of C₅₇H₁₁₀O₆ to H₂O is 2:110. The moles of H₂O produced are 110/2 × 0.82 mol = 45 mol
Step 5: Calculate the mass corresponding to 45 moles of H₂O
The molar mass of H₂O is 18.02 g/mol.
45 mol × 18.02 g/mol = 8.1 × 10² g
Determine where each type of cleaning solution should be discarded after use. Solvent used to rinse chemicals out of a beaker ______Acid solution used to clean a crucible _________Water used to rinse detergent out of a flask ________
Answer:
Acidic solution used to clean a crucible
Explanation:
This liquid dissolves alcoholic solvents such as crucible, that is why it was selected as the ideal for cleaning.
Although it would be ideal to know in detail which chemical compound is the one you want to clean so that the cleaning technique has better effectiveness.
WASTE CONTAINER refers to the solvent used to rinse chemicals out of a beaker, and it also refers to the acid solution used to clean a crucible. Water used to rinse the detergent out of a flask refer to the SINK.
The disposal containers in a lab can be used for recycling, disposal of trash, glassware disposal box, sharp box, etc.A waste container is a container usually used to dispose of waste in a laboratory, which may be made of plastic.Moreover, a laboratory sink can be used to wash tools and/or hands without the hazard of damaging the health or the sink.In conclusion, WASTE CONTAINER refers to the solvent used to rinse chemicals out of a beaker, and it also refers to the acid solution used to clean a crucible. Water used to rinse the detergent out of a flask refer to the SINK.
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If it takes 38.70cm of 1.90M NaOH to neutralize 10.30cm of H2SO4 in a battery, what is the molarity of H2SO4?
Answer:
The molarity of the acid, H₂SO₄ is 3.57 M
Explanation:
We'll begin by writing the balanced equation for the reaction. This is illustrated below:
H₂SO₄ + 2NaOH —> Na₂SO₄ + 2H₂O
From the balanced equation above,
Mole ratio of the acid, H₂SO₄ (nₐ) = 1
Mole ratio of the base, NaOH (n₆) = 2
Finally, we shall determine the molarity of the acid, H₂SO₄. This can be obtained as follow:
Volume of base, NaOH (V₆) = 38.70 cm³
Molarity of base, NaOH (M₆) = 1.90M
Volume of acid, H₂SO₄ (Vₐ) = 10.30 cm³
Molarity of acid, H₂SO₄ (Mₐ) =?
MₐVₐ / M₆V₆ = nₐ/n₆
Mₐ × 10.3 / 1.9 × 38.70 = 1/2
Mₐ × 10.3 / 73.53 = 1/2
Cross multiply
Mₐ × 10.3 × 2 = 73.53 × 1
Mₐ × 20.6 = 73.53
Divide both side by 20.6
Mₐ = 73.53 / 20.6
Mₐ = 3.57 M
Thus, the molarity of the acid, H₂SO₄ is 3.57 M
Were any of your substances difficult to identify as polar, nonpolar, or ionic? Explain.
Answer:
See explanation
Explanation:
A substance is classified as polar, nonpolar or ionic based on its behavior.
For the substances identified, there was no difficult in identifying each as polar, nonpolar, or ionic because since it was quite to easy identify where each belongs by looking out for whether it mixes or dissolves in our experiment.
Every substance in the experiment either mixed or dissolved during the experiment.
You can use solid, wedged, and dashed lines to better represent the 3D structure of molecules. The solid lines represent bonds in the plane of the paper, wedged lines represent a bond coming out of the plane, and the dashed line represents a bond going back behind the plane of the paper. Draw a representation of methane that better depicts its 3D structure.
Answer:
See explanation and image attached
Explanation:
Often times, there is a need for a three dimensional representation of a molecule on paper. These three dimensional representations give us an idea of what the molecule really looks like if we were to be looking at it physically.
In order to make a three dimensional representation, we use wedged and dashed bonds. The wedged bonds are coming out of the plane of the paper towards you while the dashed bonds are going into the plane of the paper away from you.
In the image attached, you will find the three dimensional representation of the methane molecule.
For the reaction of ammonia (NH3) with oxygen (O2) to produce water and nitric oxide (NO), how many moles of water are produced when 2.2 moles of ammonia are reacted?
Answer:
3.3 moles of H₂O.
Explanation:
We'll begin by writing the balanced equation for the reaction. This is illustrated below:
4NH₃ + 5O₂ —> 6H₂O + 4NO
From the balanced equation above,
4 moles of NH₃ reacted to produce 6 moles of H₂O.
Finally, we shall determine the number of mole of H₂O produced by the reaction of 2.2 moles of NH₃. This can be obtained as follow :
From the balanced equation above,
4 moles of NH₃ reacted to produce 6 moles of H₂O.
Therefore, 2.2 moles of NH₃ will react to produce = (2.2 × 6)/4 = 3.3 moles of H₂O.
Thus, 3.3 moles of H₂O were obtained from the reaction.
The gas carbon dioxide is a pure substance. Which of the following is true about carbon dioxide? (5 points)
Select one:
a. Carbon and oxygen are chemically bonded in it.
b. Carbon and oxygen retain their original identity in it.
c. It can be separated into carbon and oxygen using physical methods.
d. The proportion of carbon and oxygen is different in different samples of the gas.
Answer:
Carbon and oxygen are chemically bonded in it.
Explanation:
The other answer choices do not apply for compounds, but rather for mixtures instead.
Temperature can weather rocks because A heat can cause minerals to oxidize B. most rocks do not absorb heat evenly C. water contracts when it freezes D. rocks usually melt in the hot sun
Answer:
b
Explanation:
it is not c because water expands when it freezes.
A rock's mass is a:
A. all of the above
B. chemical property
C. physical property
D. constant property
Answer:
all of the above
Explanation:
now I will bless you with this-
A gray element that borders on the zigzag line of the periodic table, is ductile and malleable, but is not a very good conductor of heat or electricity is known as which of the following?
A. metal
B. halogen
C. metalloid
D. nonmetal
A gray element that borders on the zigzag line of the periodic table, is ductile and malleable, but is not a very good conductor of heat or electricity is known as metalloid. The correct option is option C.
What is periodic table?In chemistry, a periodic table is an orderly arrangement of each of the chemical elements along order of atomic number is, the total amount of protons inside the atomic nucleus.
Whenever the chemical elements stand grouped in this manner, there is a recurrent pattern in their characteristics known as the "periodic law," in which elements within a single column (group) exhibit comparable qualities. A gray element that borders on the zigzag line of the periodic table, is ductile and malleable, but is not a very good conductor of heat or electricity is known as metalloid.
Therefore, the correct option is option C.
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A chemical reaction takes place inside a flask submerged in a water bath. The water bath contains 6.50kg of water at 24.2°C. During the reaction 88.2kJ of heat flows out of the flask and into the bath.Calculate the new temperature of the water bath. You can assume the specific heat capacity of water under these conditions is 4.18·J·g−1K−1. Be sure your answer has the correct number of significant digits.
Answer:
27.4°C
Explanation:
Using the equation:
Q = m*C*T
Where Q is heat added,
m the mass of water
C specific heat of water (4.18J/g°C)
And T the increase in temperature
We can solve for the increase in temperature and thus, the final temperature of water:
Q = 88200J; m = 6500g:
88200J = 6500g*4.18J/g°C*T
3.2°C = T = increase in temperature
Final temperature is:
24.2°C + 3.2°C =
27.4°Ca sample of fully saturated clay weighs 1350 g in its natural state and 975 g after drying. what is the natural water content of the soil
Answer:
The soil has a percentage of water by mass of 27.8 %.
Explanation:
Keeping in mind that
Mass of Clay = Mass of water + Mass of Dry Soilwe can calculate the mass of water:
1350 g = Mass of Water + 975 gMass of Water = 375 gWe can then calculate the mass percentage of water in the soil:
375 / 1350 * 100% = 27.8 %The best known Lepton is the _________________.
a
electron
b
boson
c
fermion
d
hadron
e
neutron
f
proton
Answer:
Electron (e-)
Explanation:
An electron is just one of the fundamental particles
Answer:heyyyy
Explanation:
An example of electrical energy is the battery from your cell phone
Answer/Explanation:
This electrical energy now travels through the phone supplying the phone with electricity. Batteries in a cell phone supply chemical energy to electric charges. The electric charges use the energy to be put into motion.
Find the mass in grams of 1.38 moles of Sr
Answer:
116.78 grams.
Explanation:
1 mol of Strontium (Sr) = 87.62 grams
1.38 mol of Strontium = x
Cross Multiply
1 * x = 1.38 * 87.62
x = 116.78 grams
In the kinetic theory, the particles in a gas
A. move independently of each other.
B. have attractive and repulsive forces.
C. move slowly.
D. are relatively close together.
Answer:
Im pretty sure its B
Sorry if Im wrong
Explanation:
Have a wonderful day!!!<3
Answer:
The only answer that could apply to a gas is A
Explanation:
A state of matter where the particles that make up a substance start to break apart
Answer:
Liquid
Explanation:
Which of the following has the largest atomic radius?
Answer:
b
Explanation:
In a chemical change
A. materials retain their properties.
B. materials change their properties.
C. new materials do not form.
D. new materials formed are always in liquid form.
Answer:
B. materials change their properties.
Explanation:
In a chemical change, materials often change their properties because a re-arrangement of atoms takes place.
A chemical change is one in which new kind of matter is formed.
It is always accompanied by energy changes.
Chemical changes are not reversible. They lead to the production of new kinds of matter It involves mass changesRequires considerable amount of energyHELP IT’S ABOUT TO BE DUE!
A chemist is studying the rate of the Haber synthesis: N2 + 3H2 2NH3
Starting with a closed reactor containing 1.25 mol/L of N2 and 0.50 mol/L of H2, the chemist finds that the H2 concentration has fallen to 0.25 mol/L in 44 seconds.What is the N2 concentration after 44 seconds?
Answer:
1.17 M
Explanation:
Step 1: Write the balanced equation
N₂ + 3 H₂ ⇒ 2 NH₃
Step 2: Calculate the rate of disappearance of H₂
We will use the following expression.
rH₂ = - Δ[H₂]/t = - (0.25 M - 0.50 M)/44 s = 0.0057 M/s
Step 3: Calculate the rate of disappearance of N₂
The molar ratio of N₂ to H₂ is 1:3.
0.0057 mol H₂/L.s × 1 mol N₂/3 mol H₂ = 0.0019 mol N₂/L.s
Step 4: Calculate the final concentration of N₂
We will use the following expression.
[N₂] = [N₂]₀ - rN₂ × t
[N₂] = 1.25 mol/L - 0.0019 mol/L.s × 44 s
[N₂] = 1.17 M
Describe the relationship between kinetic energy and the states of matter?
PLS HELP I DONT SCIENCE HELP ASAP HELP
Answer:
The kinetic molecular theory of matter states that: Matter is made up of particles that are constantly moving. All particles have energy, but the energy varies depending on the temperature the sample of matter is in. This in turn determines whether the substance exists in the solid, liquid, or gaseous state.
Explanation:
What is an ecosystem? ?
Answer:
An ecosystem is a community or group of living organisms that live in and interact with each other in a specific environment.
Explanation:
That's the most straight forward explanation I could come up with
