The half-life of scandium-46 is determined by noting that after 252 days, the mass of the isotope reduces from 12.0 g to 1.5 g, which is 1/8 of the original mass, indicating that three half-lives have passed. Dividing the total time by 3 gives us a half-life of 84 days for scandium-46.
To determine the half-life of scandium-46, we use the fact that after a certain number of half-lives, the remaining mass of a radioactive substance is half of its initial mass after each half-life period. In the given problem, a 12.0-g sample of scandium-46 decays to 1.5 g after 252 days. This decay represents a reduction to 1/8 of the original mass, indicating that three half-lives have passed (since 12.0 / 2 / 2 / 2 = 1.5).
Initial mass of scandium-46: 12.0 gFinal mass of scandium-46 after 252 days: 1.5 gMass reduction to 1/8 indicates 3 half-lives.Since 3 half-lives are equivalent to 252 days, we can find the length of a single half-life by dividing the total time by 3:
252 days ÷ 3 = 84 days
Therefore, the half-life of scandium-46 is 84 days.
What is the reason for the change in ionization energy as you go down a group
Ionization energy of an atom decreases down a group. It is due to the increase in the number of electrons and orbitals and thus screening of electrons reduces the nuclear pull.
What is ionization energy?Ionization energy is the minimum energy required to remove the loosely bound valence electron from an atom. From left to right in periodic table, the electronegativity of atoms increases thereby the ionization energy.
The positive charge of protons in the nucleus attracts the revolving electrons and each electron experiences a nuclear attractive pull which keep the electrons surrounds the nucleus.
However, one electron is shielded from the attractive pulling by its neighboring electrons and this shielding or screening increases with increases with increase in number of electrons Hence as the shielding increases, the net nuclear force decreases make it easy to remove the valence electron.
Down a group, the number of shells or orbitals increases and the electrons becomes more far from the nucleus and thus more shielded results in the decrease in ionization energy.
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Describe the three ways heat can be transferred-radiation, conduction, and convection
Final answer:
Heat is transferred in three ways: conduction through direct contact, convection by fluid movement, and radiation through electromagnetic waves. Each method requires a temperature difference and can occur together.
Explanation:
Heat Transfer Methods
Heat transfer occurs through three primary methods: conduction, convection, and radiation. These processes are all driven by a temperature difference between regions or objects.
Conduction
Conduction is the transfer of heat through direct contact between materials. The rate of heat transfer (Q/t) in conduction is proportional to the temperature difference between the two objects and the area in contact, and inversely proportional to the distance between them.
Convection
Convection involves the transfer of heat by the physical movement of fluid (such as gases or liquids). This method occurs in natural phenomena like wind patterns, ocean currents, and even in heating up a pot of water on the stove.
Radiation
Radiation refers to the transfer of heat through electromagnetic waves, such as the heat from the sun reaching Earth or heat emitted from a light bulb.
These methods can occur simultaneously in various processes and are essential for understanding how heat is transferred in different contexts.
Describe several products of photosynthesis important to humans
Which star is hotter,but less luminous, than polaris
How do ionic compounds and molecular compounds differ in their relative melting and boiling points? which would you expect to have the higher melting point? cao or cs2?
Answer:
Ionic compounds typically have much higher melting points than molecular compounds. ... To melt a molecular substance, you need to break these weak intermolecular forces between neutral molecules, which is why ionic compounds generally have much higher melting points than molecular compounds.
Explanation:
In a metallic bond, electrons ____?
In a metallic bond, electrons are delocalized, meaning they are free to move around and are not associated with a single atom, forming a 'sea of electrons' around metal cations
In a metallic bond, electrons are delocalized. This means that the valence electrons are not associated with any single metal atom but are free to move throughout the entire structure of the metal. These delocalized electrons form a 'sea of electrons' around the metal cations (positive ions), leading to the characteristic properties of metals, such as conductivity of electricity and heat, ductility, and malleability.
What element is used to cross-link the hydrocarbon chains when natural rubber undergoes vulcanization?
Which of the following is an example of a chemical change?
water boiling to produce a gas
baking soda and vinegar combining to form a gas and a solid
grinding cinnamon and sugar together
adding hot water to freeze-dried coffee
What is the heat capacity of 170 g of liquid water?
The heat capacity of a substance is the amount of heat needed to raise its temperature by one degree Celsius. In the case of 170g of water, with a specific heat capacity of 4.18 J/g°C, the heat capacity would be approximately 710.6 J/°C.
Explanation:The heat capacity of a substance is defined as the amount of heat required to raise the temperature of that substance by one degree Celsius. For water, the specific heat capacity is around 4.18 joules per gram per degree Celsius. Therefore, to find the heat capacity of 170 g of water, we multiply the mass of the water by its specific heat capacity.
So, the calculation would go as follows:
Heat capacity = mass of water * specific heat capacity Heat capacity = 170 g * 4.18 J/g°C Therefore, the heat capacity of 170 g of water is approximately 710.6 J/°C.
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Based on these data, what is the average atomic mass of element b? 10.01 10.51 10.81 11.01
Based on these data,10.81 is the average atomic mass of element b. Therefore, option C is correct.
What is atomic mass ?An atom's mass is its atomic mass. Although the kilogram is the SI measure of mass, the unified atomic mass unit, or dalton, is a common way to express atomic mass. An unbound carbon-12 atom in its ground state has a mass of 112 of a Da.
The total number of protons and neutrons in an isotope's nucleus is referred to as the mass number. This is due to the fact that each proton and neutron has a mass of one atomic mass unit (amu). You may get the mass of the atom by multiplying the total number of protons and neutrons by 1 amu.
From the given table,
Element B has two isotopes i.e.,
One with a mass of 10.01 and a relative abundance of 19,91,
while the another has a mass of 11.01 and a relative abundance of 80.09.
The average atomic mass
= ( 10.01 × 19.91 ) + ( 11.01 × 80.09)
= 1.99 + 8.817
= 10.81
Thus, option C is correct.
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Your question is incomplete, probably your question was
The table below gives the data that is needed to calculate the average atomic mass of element B. Isotope Atomic mass (amu) Relative abundance (%) B-10 10.01 19.91 B-11 11.01 80.09 Based on these data, what is the average atomic mass of element B? 10.01 10.51 10.81 11.01
If a neutral atom gains electrons, what type of particle is formed?
The electron microscope has been widely used to obtain highly magnified images of biological and other types of materials. when an electron is accelerated through a particular potential field, it attains a speed of 4.15 106 m/s. what is the characteristic wavelength of this electron?
A compound composed of only carbon and chlorine is 85.5% chlorine by mass. propose a lewis structure for the lightest of the possible compounds that allows each atom to have a complete octet without formal charges. draw the molecule by placing atoms on the grid and connecting them with bonds. include all lone pairs of electrons.
The lightest compound of carbon and chlorine is carbon tetrachloride (CCl4), which fulfils the octet rule for all atoms without any formal charges. The carbon forms four covalent bonds with the chlorine atoms, and each chlorine atom has three lone pairs of electrons.
Explanation:The question is asking for a Lewis structure for a compound made from carbon and chlorine that would have each atom have a complete octet of electrons and no formal charges. Based on the given mass percentage, the simplest possibility would be carbon tetrachloride (CCl4). Carbon has four electrons in its outer shell and chlorine has seven. In a CCl4 molecule, the carbon atom forms four covalent bonds with the chlorine atoms, using one of the electrons in carbon's outer shell and one electron from each chlorine atom. Thus, each atom has an octet of electrons. Carbon tetrachloride is composed of a central carbon atom bonded to four chlorine atoms in a tetrahedral shape. The Lewis structure would have carbon in the center, with a bond to each of the four chlorine atoms, and each chlorine atom will have three lone pairs of electrons.
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How do the properties of the p block metals compare with those of the metals in the s and d blocks?
Final answer:
p-block metals have higher electronegativities and ionization energies compared to the reactive s-block metals. d-block metals, known as transition metals, posses variable oxidation states and form colorful compounds, setting them apart from p-block and s-block elements.
Explanation:
The properties of p-block metals differ considerably compared to those in the s-block and d-block. One of the most distinguishing features of p-block metals is their position on the periodic table - they are found in the right-most six columns. Elements in the p-block, which include both metals and nonmetals, typically have higher electronegativities and ionization energies than s-block elements, which consists mostly of metals with low electronegativities like the alkali and alkaline earth metals.
d-block elements, also known as transition metals, have a much larger range of oxidation states and, due to incomplete inner d subshells, typically exhibit properties like colorful compounds, variable oxidation states, and often function as good catalysts. Electronegativity and electron affinity generally increase from left to right across the periodic table, affecting the chemical properties of these elements.
s-block elements tend to be softer and more reactive due to their single valence electron (alkali metals) or two valence electrons (alkaline earth metals). They usually have lower melting and boiling points compared to most d-block metals. The d-block elements are characterized by their partially filled d-orbitals which allow them to form a variety of complex ions and colored compounds.
What are group 6a elements likely to do when they form ions-gain electrons or lose them?what are group 6a elements likely to do when they form ions-gain electrons or lose them?lose electronsgain electrons?
One of the alkali metals reacts with oxygen to form a solid white substance. when this substance is dissolved in water, the solution gives a positive test for hydrogen peroxide, h2o2. when the solution is tested in a burner flame, a lilac-purple flame is produced. what is the likely identity of the metal?
Answer:
Potassium (K)
Explanation:
First, you need to know the possible alkali metals, which are:
Sodium (Na), Litium (Li), Potassium (K) and Cesium (Cs), rubidium (Rb).
Now, the reaction that is taking place is the following:
M + O2 ------> M2On
Where n should be the oxidation state of the metal. In this case, most of the alkalin metals have an oxidation state of +1, so, this number should be 1. However some elements can produce the peroxyde, like litium, sodium and potassium.
The following reaction would be:
M2O + H2O --------> MOH
Now, the hint here is that the solution is tested with a flame. This, would be, the final hint to know which element this is.
In the case of sodium, litium and potassium, the reactions being held are as following:
Li + O2 ------> Li2O2 Li2O2 + 2H2O ------> 2LiOH + H2O2
Na + O2 ------> Na2O2 Na2O2 + 2H2O ------> 2NaOH + H2O2
K + O2 ------> K2O2 K2O2 + 2H2O ------> 2KOH + H2O2
Now, all of these elements throw a different color in the flame. Litium is a red or crimson. Sodium is usually yellow, and finally the potassium is always purple.
Therefore the identity of this metal would have to be potassium.
How many grams of glucose are needed to prepare 400. ml of a 2.0%(m/v) glucose solution?
Answer:8 grams of glucose are needed to prepare 400. ml of a 2.0%(m/v) glucose solution.
Explanation:
Volume of the solution = 400 mL
Mass by volume percentage of the solution = 2%
Mass of the glucose = m
The mass by volume percent is given by formula ;
[tex](m/v\%)=\frac{\text{mass of the solute}}{\text{Volume of the solution}}\times 100[/tex]
[tex]2\%=\frac{m}{400}\times 100[/tex]
m = 8 g
8 grams of glucose are needed to prepare 400. ml of a 2.0%(m/v) glucose solution.
Mass Concentration is generally denoted as mass of solute (in grams) per ml volume of solution.
Mass Concentration:
It is generally denoted as mass of solute (in grams) per ml volume of solution. It can be calculated by formula,
[tex]\bold {p = \frac{m}{v} \times 100 }[/tex]
Where,
p = mass concentration (m/v%) = 2%
m = mass in grams = ?
v = volume in mL = 400mL
Put the values in the formula
[tex]\bold {2 = \frac{m}{400} \times 100 }[/tex]
[tex]\bold { m = 8 }[/tex]
Hence, we can conclude that the 8 g of glucose is needed to prepare 400mL of a 2%(m/v) solution.
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What is the mass of a 300 ml sample of gaseous hydrogen chloride at 2.0 atm and 30c?
Ideal gas law is valid only for ideal gas not for vanderwaal gas. Ideal gas is a hypothetical gas. Vanderwaal gas can behave as ideal gas at low pressure and high temperature. Therefore, the mass of a 300 ml sample of gaseous hydrogen chloride at 2.0 atm and 30°C is 0.00868g.
What is ideal gas equation?Ideal gas equation is the mathematical expression that relates pressure volume and temperature.
Mathematically the relation between Pressure, volume and temperature can be given as
PV=nRT
where,
P = pressure of gas
V= volume of gas
n =number of moles of gas
T =temperature of gas
R = Gas constant = 0.0821 L.atm/K.mol
substituting all the given values in the above equation
(2 )(0.3 ) = n(8.314 )(303)
0.6 = n(2519.142)
n = 0.00023818 mols of HCl
mass of HCl= 0.00023818 mols of HCl ×36.46g of HCl/ 1 mol of HCl
mass of HCl = 0.00868g
Therefore, the mass of a 300 ml sample of gaseous hydrogen chloride at 2.0 atm and 30°C is 0.00868g.
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Final answer:
To find the mass of a 300 ml sample of gaseous hydrogen chloride at 2.0 atm and 30°C, use the Ideal Gas Law to determine the number of moles, then multiply by the molar mass of HCl. The approximate mass is 0.89 grams.
Explanation:
To calculate the mass of a 300 ml sample of gaseous hydrogen chloride at 2.0 atm and 30°C, we can use the Ideal Gas Law, which is PV = nRT. In this case, we need to rearrange the equation to solve for n (the number of moles), then convert moles to mass using the molar mass of HCl.
First, convert the volume from milliliters to liters: 300 ml = 0.300 L.
Next, since the temperature is given in degrees Celsius, convert it to Kelvin: T(K) = 30°C + 273.15 = 303.15 K.
The Ideal Gas Law in terms of n is n = PV / RT. Here, P is the pressure in atm (2.0 atm), V is the volume in liters (0.300 L), R is the ideal gas constant (0.0821 L·atm/K·mol), and T is the temperature in Kelvin (303.15 K).
Substituting the values:
n = (2.0 atm * 0.300 L) / (0.0821 L·atm/K·mol * 303.15 K)n ≈ 0.0244 moles (rounded to the correct number of significant figures)Finally, we find the mass by multiplying the number of moles by the molar mass of HCl, which is approximately 36.46 g/mol.
Mass = n * molar mass of HCl = 0.0244 moles * 36.46 g/mol ≈ 0.89 g (rounded to two significant figures)
The mass of the 300 ml sample of gaseous hydrogen chloride at 2.0 atm and 30°C is approximately 0.89 grams.
Which base is the strongest for the given [H+]?
A group of two or more atoms held together by mutually shared electrons are called ________.
What is the practical use of scientific knowledge to solve everyday problems and improve lives?
A. research
B. publications
C. technology
D. patents
Openstudy the deflection of alpha particles in rutherford's gold foil experiments resulted in what change to the atomic model?
Calculate the molarity of a solution that contains 15.7g of caco3 dissolved in enough water to make 275 ml of solution
Taking into account the definition of molarity, the molarity of a solution that contains 15.7g of CaCO₃ dissolved in enough water to make 275 mL of solution is 0.57 [tex]\frac{moles}{liter}[/tex].
Definition of molarityMolar concentration or molarity is a measure of the concentration of a solute in a solution and indicates the number of moles of solute that are dissolved in a given volume.
The molarity of a solution is calculated by dividing the moles of solute by the volume of the solution:
[tex]Molarity= \frac{number of moles}{volume}[/tex]
Molarity is expressed in units [tex]\frac{moles}{liter}[/tex].
This caseIn this case, you have:
number of moles: [tex]15.7 gramsx\frac{1 mole}{100 grams} = 0.157 moles[/tex] , being 100 [tex]\frac{grams}{mole}[/tex] the molar mass of CaCO₃volume: 275 mL= 0.275 L, being 1000 mL= 1 LReplacing in the definition of molarity:
[tex]Molarity= \frac{0.157 moles}{0.275 L}[/tex]
Solving:
Molarity= 0.57 [tex]\frac{moles}{liter}[/tex]
Finally, the molarity of a solution that contains 15.7g of CaCO₃ dissolved in enough water to make 275 mL of solution is 0.57 [tex]\frac{moles}{liter}[/tex].
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what is the volume of 1 mole of helium gas when the pressure is 1.47 atm and the temperature is 287k
The volume of 1 mole of helium gas when the pressure is 1.47 atm and the temperature is 287k is 16.02 litres.
What is combined gas law?The combined gas law is the law of of gaseous state which is made by combination of Boyle's law, Charle's law, Avogadro's law and Gay Lussac's law.
It is a mathematical expression that relates Pressure, Volume and Temperature.
(P1 × V1)÷T1 = (P2 × V2)÷T2
Also, we can simply write it as
PV = nRT
P = 1.47 atm
V = ?
n = 1
R = 0.0821
T = 287K
V = nRT ÷ P
V = 16.02 litres
Therefore, The volume of 1 mole of helium gas when the pressure is 1.47 atm and the temperature is 287k is 16.02 litres.
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Brad and Juan conducted several tests to determine the properties of silver metal. They noted that is was white, and conducted both electricity and heat. They computed the density to be 10.49 g/cm3. Silver did not react with water but in nitric acid, gas was released. What evidence supports a chemical change in the silver? A) Silver conducts electricity. B) Silver reacts with nitric acid to produce a gas. C) The color of silver at room temperature is white. D) Silver conducted heat and as the temperature increased, became more malleable.
Answer:
B because it should be
Explanation:
and that is right answer??
How many molecules of ammonia are present in 3.0 g of ammonia (Formula = NH3)?
A) 1.2 × 1024
B) 1.8 × 101
C) 1.1 × 1023
D) 2.9 × 10-25
E) 3.6 × 1023
The number of molecules of ammonia present in 3.0 g of ammonia is equal to 1.1×10²³.
What is Avogadro's number?Avogadro’s number expressed the number of units in one mole of any substance. Generally, these units can be atoms, ions, electrons, protons, or molecules depending upon the type of the reaction or reactant and product.
The value of Avogadro’s number is 6.022×10²³. Avogadro’s number is usually denoted by the symbol ‘N[tex]_A[/tex]’.
Given, the mass of the ammonia = 3g
The molecular mass of the ammonia (NH₃) = 14 + 3(1) = 17g
As one mole of the ammonia contains molecules = Avogadro number
It means 17 grams of ammonia has molecules = 6.022×10²³
Then, 3 grams of ammonia will have molecules of ammonia
= 6.022 × 10²³ × (3/17)
= 1.1 × 10²³ molecules
Therefore, the number of molecules of ammonia in 3 g of ammonia is 1.1 × 10²³ molecules.
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Final answer:
To find the number of ammonia molecules in 3.0g of ammonia, you calculate moles from the given mass and molar mass, then use Avogadro's number to find the molecule quantity. The result is approximately 1.06 × 10²³ molecules, matching closely to option C in the question.
Explanation:
To determine how many molecules of ammonia (NH₃) are present in 3.0g of ammonia, we first need to calculate the molar mass of NH₃. The atomic masses of nitrogen (N) and hydrogen (H) are approximately 14.01 g/mol and 1.01 g/mol, respectively. A single molecule of NH₃ consists of one nitrogen atom and three hydrogen atoms, which gives us:
Molar mass of NH₃ = (1 × 14.01 g/mol) + (3 × 1.01 g/mol) = 14.01 g/mol + 3.03 g/mol = 17.04 g/mol
Next, we use the molar mass to convert grams of NH₃ to moles:
Moles of NH₃ = mass (g) ÷ molar mass (g/mol) = 3.0 g ÷ 17.04 g/mol = 0.176 moles of NH₃
Now we can use Avogadro's number (≈ 6.022 × 10²³ molecules/mol) to find the number of molecules:
Number of molecules = moles × Avogadro's number = 0.176 moles × 6.022 × 10²³ molecules/mol
This calculation gives us approximately:
Number of molecules ≈ 1.06 × 10²³ molecules of NH₃
Looking at the options provided, the closest answer to our calculated value is C) 1.1 × 10²³, which must be a rounded version of the value we obtained.
What is the study of the mass relationships among reactants and products in a chemical reaction?
Which two trends increase when one moves across a period from left to right?
atomic size and size of cations
ionization energy and atomic size
ionization energy and electronegativity
electronegativity and atomic size
The change of phase from a solid to a gas is called
I believe its sublimation. An example of it could be like dry ice.
Hope that helps!
Answer : The change of phase from a solid to a gas is called sublimation.
Explanation :
Melting or fusion : It is a type of process in which the phase changes from solid state to liquid state at constant temperature.
Freezing : It is a type of process in which the phase changes from liquid state to solid state at constant temperature.
Evaporation : It is a type of process in which the phase changes from liquid state to gaseous state at constant temperature.
Condensation : It is a type of process in which the phase changes from gaseous state to liquid state at constant temperature.
Sublimation : It is a type of process in which the phase changes from solid state to gaseous state without passing through the liquid state at constant temperature.
Deposition : It is a type of process in which the phase changes from gaseous state to solid state without passing through the liquid state at constant temperature.
Hence, the change of phase from a solid to a gas is called sublimation.
What causes pressure in a closed container of gas?
an increase in the thickness of the container walls
collisions between the particles of gas and the container walls
an increase in the size of the particles of the gas
Answer: collisions between the particles of gas and the container walls
Explanation:
Pressure is defined as the force acting per unit area.
[tex]Pressure=\frac{Force}{Area}[/tex]
Thus the pressure increases as the force increases and area decreases.
The particles present in a gas have least inter molecular forces of attraction ad thus the particles are in constant motion. they keep on colliding with other particles and the walls of the container in which they are kept.
Pressure of the gas molecules is due to the bombardment of gas molecules with other gas molecules and the walls of the container.
Pressure in a closed gas container is caused by collisions between the gas particles and the walls of the container. Changes in the number or temperature of the gas particles can alter the pressure.
In a closed container of gas, pressure is caused primarily by the collisions between the particles of the gas and the walls of the container. These particles are in constant, random motion and when they hit the container walls, they exert a force on it, resulting in pressure. Neither the thickness of the container walls nor the size of the gas particles directly affect the pressure within the container. However, increasing the number of gas particles (for instance, by adding more gas) or increasing their temperature (which speeds up their motion), would increase the pressure, because these changes result in more frequent and/or harder collisions with the container walls.
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