Hence, 5.1 * 10^-11 alpha particles is being emitted each second by the sample.
What is half life?The term half life is the time taken for only half of the original amount of radioactive nuclides to remain.
Thus, we have that the half life is 432.2 years or 1.36 * 10^10 s.
k = 0.693/ 1.36 * 10^10 s
k = 5.1 * 10^-11 alpha particles per second.
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31. calculate the amount of energy released as heat by the freezing of 13.3 g of a liquid substance, given that the substance has a molar mass of 82.9 g/mol and a molar enthalpy of fusion of 4.60 kj/mol.
From the calculations, the heat of fusion of the substance is 0.73 kJ
What is is the heat of freezing?The heat of freezing is the energy released when the substance is converted from liquid to solid.
Now we know that the molar mass of the substance is 82.9 g/mol hence the number of moles of the substance is; 13.3 g /82.9 g/mol = 0.16 moles
Now the heat of fusion shall be;
H = 4.60 kj/mol * 0.16 moles
H = 0.73 kJ
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Rank the following atoms from the most electronegative (top) to the least electronegative (bottom).
Answer:
Oxygen
Carbon
Silicon
Hydrogen
Beryllium
Lithium
Explanation:
The trend of electronegativity is that electronegativity increases across a period, and decreases down a group. This means that the elements in the top right of the periodic table are the most electronegative (excluding noble gases)
Knowing this, let's rearrange the elements given in the question.
We have oxygen, carbon, silicon, hydrogen, lithium, and beryllium.
First let's separate the elements on the left and right side of the periodic table:
Left: Hydrogen, lithium, beryllium.
Right: Oxygen, carbon, silicon.
The elements on the right are more electronegative than the left.
Let's focus on the right elements.
Oxygen would be the most electronegative because it is furthest to the right.
Next would be carbon, because it is one higher than silicon.
Then, it would be silicon.
Now, let's look at the left elements.
Hydrogen would be the most electronegative because it is the highest.
Next would be beryllium because it is to the right of lithium
Last would be lithium because it is the most left, and down the group.
So, the final answer will be
Oxygen
Carbon
Silicon
Hydrogen
Beryllium
Lithium
Hope this helps!! If you have any questions about what I said please leave them down in the comments!
how can you explain that even though you continue to add pure water into a substance, even though the resultant ph might differ a little, the acidity or alkalinity of substance still remains the same to that of substance?
Addition of pure water does not change pH of a solution because pure water has neutral pH.
Why the pH does not change when pure water is added?Even though you continue to add pure water into a substance, the acidity or alkalinity of substance still remains the same to that of substance because pure water has neutral pH which can't change the acidity or alkalinity of a solution.
So we can conclude that addition of pure water does not change pH of a solution because pure water has neutral pH.
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Which of these is a characteristic of chemical change?
Select one:
a. turns cloudy
b. melts into liquid state
c. boil to a gas
d. break into smaller pieces
Characteristic of Chemical Change: c. boil to a gas
1. Chemical changes involve the transformation of one substance into another substance with different properties.
2. Option c, "boil to a gas," is a characteristic of chemical change.
3. When a substance undergoes a chemical change, it may experience a change in its physical state, such as boiling, as a result of the chemical reactions occurring at the molecular level.
4. Boiling refers to the process in which a substance changes from a liquid state to a gaseous state, usually by the absorption of heat energy.
5. During a chemical change, the bonds between atoms or molecules in the substance are broken and rearranged, leading to the formation of new substances.
6. The change in state from a liquid to a gas indicates that a chemical reaction has taken place, resulting in the formation of different chemical compounds.
7. On the other hand, options a and b, turning cloudy and melting into a liquid state, are characteristics of physical changes rather than chemical changes.
8. Turning cloudy generally occurs due to the formation of suspended particles in a substance, while melting refers to the transition from a solid to a liquid state without the formation of new substances.
9. Option d, breaking into smaller pieces, can also be a characteristic of physical changes, such as when a solid is mechanically fragmented, without any alteration in its chemical composition.
10. Therefore, among the given options, the characteristic that specifically indicates a chemical change is c, boiling to a gas.
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identify the world that is being described in each statement about the previous topic afterwards write the first letter of each answer to the corresponding number of missing letters to reveal the words below
help me plss
Answer:
5. Richter magnitude scale
6. Magma
7. Epicenter
8. Seismographs/seismometers
9. Extinct volcanoes
10. Seismogram
Gas Law
In a mixture of carbon dioxide and oxygen, 40.0% of the gas pressure is exerted by oxygen. If the total pressure is 115 mmHg, what is the pressure of the carbon dioxide in
atm?
69 mmHg pressure is exerted by oxygen if 40% of the gas pressure is exerted by the oxygen gas.
What is pressure?Pressure is defined to be the amount of force exerted per area
40% of pressure is exerted by oxygen gas.
So, 60% of pressure will be exerted by carbon dioxide gas.
60% of 115 mmHg = 69 mmHg
Hence, 69 mmHg pressure is exerted by oxygen if 40% of the gas pressure is exerted by the oxygen gas.
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How many moles of electrons are transferred for each mole of o2 that reacts? justify your answer in terms of the balanced equation and the change in oxidation number of oxygen
Based on the equation of the reaction, for every 1 mole of oxygen that reacts, 4 moles of electrons are transferred.
What are redox reactions?Redox reactions are reactions in which oxidation and reduction reactions occur simultaneously to the same extent.
Oxidation reactions involves addition of oxygen or removal of oxygen.
The equation of reaction when one mole of oxygen accept ectrons is given below:
[tex]O_2 + 4e^{-} \rightarrow 2O^{2-}[/tex]
Therefore, for every 1 mole of oxygen that reacts, 4 moles of electrons are transferred.
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Some scientists believe that the mass extinction of dinosaurs was caused by the impact of a large meteorite on earth. this impact would have caused a darkening of the sky due to dust blown into the upper atmosphere. this darkening would have reduced the sizes of some ecosystems because of
The darkening of the atmosphere caused by meteorites would have reduced the sizes of some ecosystems due to less solar energy being available to plants.
What is Solar energy?This is the form of energy which is derived from the sun and is usually trapped by plants during photosynthesis.
Plants being primary producers will have less photosynthetic activity thereby leading to less food production and oxygen availability.
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How many ml of 0.50 m naoh are needed to exactly neutralize 40. ml of 0.15 m hci?
The volume of NaOH needed to neutralize 40. ml of 0.15 m Hcl acid is 12 mL.
Volume of base neededThe volume of base needed to neutralize 40. ml of 0.15 m Hcl acid is calculated as follows;
C1V1 = C2V2
V1 = (C2V2)/C1
V1 = (40 x 0.15)/(0.5)
V1 = 12 mL
Thus, the volume of NaOH needed to neutralize 40. ml of 0.15 m Hcl acid is 12 mL.
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a sample of a substance has a density of 1.75 g/cm3 and a mass of 14.7 g. What volume does the sample occupy?
The volume occupied by the sample is 8.4 cm³
What is density?The density is the ratio of mass of the object to its volume.
Given is the mass m =14.7 g and the density is 1.75 g/cm³, then the volume will be
ρ = m/ V
V =m /ρ
Substitute the values, we get
V = 14.7 /1.75
V = 8.4 cm³
Thus, the volume of the sample is 8.4 cm³.
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Metal objects, such as knifes or bullets, that come into contact with bones can leave trace evidence on them.
O True
O False
Why does hcl conduct electricity with water but not with chloroform
Answer:
ions need to be present in the water. If there are no ions in solution, no electricity is conducted. since, in water, electricity is conducted, this means that HCl completely ionizes to H + and C l − ions. However, in chloroform, since there is no conduction, HCl does not ionize and stays as the
Explanation:
When European demand for a certain solvent declined, Dow Chemical instructed its German plant to switch to manufacturing a chemical that had been imported from Louisiana and Texas. Dow Chemical would be best described as a(n)
Dow Chemical would be best described as a multinational corporation in this scenario.
What is a Multinational corporation?
This is the type of corporation which are involved in controlling production of goods and services in at least one country different from that of residence.
Dow chemical is known to have a plant in Germany and Russia thereby making it a multinational corporation.
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In industrialized states every tenth adult suffers daily, and every third occasionally, from heartburn. In Germany almost ten million people are affected by this disease. Helpful medicines against heartburn are the so-called ‘antacids’.
Antacids bound acids against an over-acidification of the stomach. The stomach acid contains hydrochloric acid (HCl, dissolved in water), which reacts with the antacid to form water, carbon dioxide and the corresponding salt. Generally, antacids are carbonates. Very common is ‘Bullrichs salt’, which uses sodium hydrogen carbonate as active ingredient. A single dose of an antacid is to be chosen in a way that it will react with two grams of hydrochloric acid. You are to formulate the instruction leaflet for a pharmaceutical company, which sells calcium carbonate (CaCO3) as an antacid. The dosing instruction says that in case of heartburn, one tablet with sufficient water is to be ingested.
But the specification, how many grams of calcium carbonate one tablet contains, is still missing…
Answer:
Antacids are medicines that counteract (neutralise) the acid in your stomach to relieve indigestion and heartburn. They come as a liquid or chewable tablets and can be bought from pharmacies and shops without a prescription.
What is the volume of a gas if 0.182 moles of the gas is at 1.99 atm and 83.4oC?
[tex]\text{Given that,}\\\\\text{Pressure,}~ P = 1.99~ \text{atm}\\ \\\text{No. of moles,}~ n = 0.182~ \text{mol.}\\\\\text{Temperature,}~ T = 83.4^{\circ}~ C = 356.4~K\\\\ \text{Molar gas constant,}~ R = 0.082~ \text{L}~ \text{atm}~ \text{mol}^{-1}~ \text{K}^{-1}\\\\\text{Volume,}~ V =?\\\\\text{We know that,}~\\\\~~~~~~~PV =nRT\\\\\implies V = \dfrac{nRT}{P}\\\\\\~~~~~~~~~~=\dfrac{0.182 \times0.082 \times 356.4 }{1.99}\\\\\\~~~~~~~~~~\approx 2.68~ \text{L.}\\\\\\[/tex]
[tex]\text{Hence the volume of the gas is 2.68 L.}[/tex]
2.68L is the volume of a gas if 0.182 moles of the gas is at 1.99 atm and 83.4°C.
What is volume?A measurement of three-dimensional space is volume. It is frequently expressed quantitatively using SI-derived units, as well as several imperial or US-standard units. Volume and the notion of length are connected. In contrast to how much space the container actually occupies, the size of a container is typically thought of as its capacity, or the quantity of liquid it could hold.
Volume was initially measured using naturally occurring vessels of a comparable shape and then with standardised containers. Arithmetic formulas can be used to quickly calculate the volume of several straightforward three-dimensional shapes. If a formula again for shape's boundary is known, it is possible to use integral calculus to determine the volumes of more complex shapes.
P×V = n×R×T
V=n×R×T /P
=0.182 ×0.082×356.4 /1.99
=2.68L
Therefore, 2.68L is the volume of a gas if 0.182 moles of the gas is at 1.99 atm and 83.4°C.
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D
Question 13
An atom has 23 protons and 29 neutrons. Which is the correct chemical symbol for this atom?
52 V
23
52 Cu
23
29 C
29 V
23
The correct chemical symbol for an atom that has 23 protons and 29 neutrons is 52/23 V. Details about chemical symbol can be found below.
What is chemical symbol?Chemical symbol is the 1- to 3-letter international code for a chemical element.
The chemical symbol of an element shows the atomic mass and mass number of the element.
The mass number of an element is the sum of the number of protons and neutrons. In this case, the mass number of the element is 23 + 29 = 52
Therefore, the correct chemical symbol for an atom that has 23 protons and 29 neutrons is 52/23 V.
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These statements describe three different reactions.
1-An atom shares electrons with another atom.
2- The nucleus of an atom is split apart.
3-An atom gains an electron from another atom.
Which reaction (s) most likely release the greatest amount of energy?
1
O2
O1 and 3
O2 and 3
An atom gains an electron from another atom. Hence, option B is the correct answer.
What is an atom?An atom is a particle of matter that uniquely defines a chemical element. An atom consists of a central nucleus that is usually surrounded by one or more electrons.
When an atom shares electrons with another atom then it results in the formation of a covalent bond.
Whereas when an atom transfer electrons from one atom to another then it results in the formation of an ionic bond.
When the nucleus of an atom splits then it represents a nuclear fission reaction and energy is released during this process.
Hence, option B is the correct answer.
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The arrows in the chart below represent phase transitions. Three bars are shown labeled Solid, Liquid, and Gas. They are connected by arrows labeled 1 to 6. Arrow 1 points from liquid to gas; arrow 2 from solid to liquid, arrow 3 from solid to gas, arrow 4 from gas to liquid, arrow 5 from liquid to solid, and arrow 6 from gas to solid. Which arrows represent the phase transitions in which heat energy is gained? 1, 2, and 3 2, 3, and 5 3, 4, and 5 4, 5, and 6 Mark this and return
The arrows that represent the phase transitions in which heat energy is gained is : (A). 1, 2 and 3
Meaning of phase transitionsPhase transitions can be defined as the changing of matter from one form to another due to the addition or gaining of heat or due to the removal or loss of heat.
Phase transitions in matter are majorly between three phases which are: Solid, Liquid and Gas.
In conclusion, The arrows that represent the phase transitions in which heat energy is gained is : (A). 1, 2 and 3
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Measurements show that unknown x compound has the following composition:
carbon 18.1%
hydrogen 2.27%
chlorine 79.8%
Write the empirical chemical formula of x.
The empirical formula of the compound with the percent composition C 18.1%, H 2.27%, Cl 79.8% is C₂H₃Cl₃.
What is an empirical formula?It is the minimum ratio between the elements that form a compound.
Step 1: Divide each percentage by the molar mass of the element.C: 18.1/12.01 = 1.51
H: 2.27/1.01 = 2.25
Cl: 79.8/35.45 = 2.25
Step 2: Divide all the numbers by the smallest one.C; 1.51/1.51 = 1
H: 2.25/1.51 ≈ 1.5
Cl: 2.25/1.51 ≈ 1.5
Step 3: Multiply all the numbers by 2 so all of them are whole.C: 1 × 2 = 2
H: 1.5 × 2 = 3
Cl: 1.5 × 2 = 3
The empirical formula is C₂H₃Cl₃.
The empirical formula of the compound with the percent composition C 18.1%, H 2.27%, Cl 79.8% is C₂H₃Cl₃.
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What is the density of a sample of charcoal with a mass of 3.0g and a volume of 10 cm^3
When 2.5 moles of oxygen gas react completely with pentane, how many moles of carbon dioxide are present?
Balanced equation: C5H12 + 8 O2 --> 5 CO2 + 6 H2O
Show work
Answer:
1.6 mol Carbon Dioxide
Explanation:
In order to convert between mols of compounds, you need to use the mole ratio. First, divide 2.5 moles of oxygen gas by 8 moles of oxygen because that is the number of moles of oxygen gas in the balanced equation. Then to find the number of moles of carbon dioxide, multiply by the 5 moles of carbon dioxide in the mole ratio. After multiplying, you get the answer 1.56 moles of carbon dioxide and with 2 significant figures present you would round to 1.6 moles.
The bac is a measurement of the amount of alcohol in:.
Answer:
Blood
Explanation:
'B' stands for 'Blood' in Blood Alcohol Content
Calculate the concentration in gdm3 of 0.85M Ammonium Carbonate solution. [C=12, N=14, H=1, N=14, 0=16]
Answer:
You need to provide a volume for the problem to be solved.
Explanation:
A solvent is added to dissolve only one mixture component and then the liquids are separated. Choose... A liquid is carefully poured out, leaving the solid behind in the container. Choose... A solid is caught on paper or a membrane while the liquid passes through. Choose... A solid mixture is heated. One component transitions directly between solid and gas. Choose...
The solid would be caught on a filter paper or membrane while the liquid passes through.
FiltrationFiltration is used to separate a mixture of insoluble substances in a liquid.
Since the aim is to separate the insoluble component of the mixture from the liquid, filtration using a suitable filter paper or membrane will be the way out.
The liquid will pass through the filter paper or the membrane while the insoluble component will be caught. This can then be dried and collected accordingly.
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when you draw a bow across a violin string which kind of wave is created in the air surrounding the string
Answer:
When the string on a violin vibrates, waves move in both directions along the string, interfering with each other. These waves are standing waves.
Explanation:
What are Standing Waves?
The Standing Waves are waves generated due to the vibrational frequency that produces reflected waves capable of interfering with the incident waves.
how to make crystals of sodium chloride without putting sodium into hydrochloric acid
Answer:
• Reacting aqueous Sodium hydroxide solution with Magnesium chloride.
Explanation:
[tex]{ \rm{2NaOH _{(aq)} + MgCl _{2(s)} \: \dashrightarrow \: 2NaCl _{(s)} + Mg(OH)_{2(aq)} }}[/tex]
Answer:
Sodium hydroxide solution + Magnesium chloride = sodium chloride crystals
Explanation:
5.6 grams of hydrogen react with some oxygen. 41.4 grams of water is the product. How much oxygen reacted (in grams)?
The amount of oxygen in grams that reacted with 5.6 g of hydrogen to produce 41.4 g of water is 36.8 g
Balanced equation2H₂ + O₂ —> 2H₂O
Molar mass of O₂ = 32 g/mole
Mass of O₂ from the balanced equation = 1 × 32 = 32 g
Molar mass of H₂O = 18 g/mole
Mass of H₂O from the balanced equation = 2 × 18 = 36 g
SUMMARY
From the balanced equation above,
36 g of H₂O was produced from 32 g of O₂
NOTE: O₂ is the limiting reactant
How to determine the mass of oxygen requiredFrom the balanced equation above,
36 g of H₂O was produced from 32 g of O₂
Therefore,
41.4 g of H₂O will be produced from = (41.4 × 32) / 36 = 36.8 g of O₂
Thus, 36.8 g of O₂ reacted to produce 41.4 g of H₂O
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What can scientists learn from radiometric dating?
A- how long ago a plant or animal lived
B- how much time it took a fossil to form
C- where a plant or animal lived
D- whether a fossil has modern relatives
Answer:
B- how much time it took a fossil to form
Explanation:
To determine the ages in years of Earth materials and the timing of geologic events such as exhumation and subduction, geologists utilize the process of radiometric decay.
Which of the following atoms require the greatest amount of ionization energy? Cu, Ag, or Au
Ionization energy is the periodic property of an element. The copper atom has the highest ionization energy among gold and silver atom.
What is ionization energy?Ionization energy is the amount of energy required for the removal of the loosely bounded electron from an atom. The ionization energy can be first, second, and third based on the number of electrons.
Ionization energy down the group decreases from top to bottom as the atomic radii of the element increase. So, the ionization energy for the given elements is Cu > Au > Ag.
Therefore, copper has the highest ionization energy.
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Which scientist determined the charge of the electron?.
Answer:
J.J. Thomson
Explanation: