After 2 half-lives, 100,000 atoms of the radioactive substance will remain.
If two half-lives have passed, the number of remaining atoms will be one-fourth (1/2 x 1/2 = 1/4) of the original number of atoms.
Therefore, the number of remaining atoms will be:
400,000 x (1/4) = 100,000 atoms
Rounding this to the nearest whole number, we get:
100,000 atoms
Therefore after 2 half-lives, 100,000 atoms of the radioactive substance will remain.
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The empirical formula of caffeine is C4H5N2O. If the molar mass of caffeine is 194.19 g/mol, what is the molecular formula of caffeine?
The molecular formula of caffeine is C₈H₁₀N₄O₂
To find the molecular formula of caffeine, we need to determine the ratio of the empirical formula to the actual molecular formula. The empirical formula gives us the smallest whole-number ratio of atoms in a compound, while the molecular formula gives us the actual number of atoms of each element in a molecule.
First, we need to calculate the empirical formula mass of caffeine:
Empirical formula mass = (4 x atomic mass of carbon) + (5 x atomic mass of hydrogen) + (2 x atomic mass of nitrogen) + (1 x atomic mass of oxygen)
Empirical formula mass = (4 x 12.01 g/mol)+ (5 x 1.01 g/mol) + (2 x 14.01 g/mol) + (1 x 16.00 g/mol)
Empirical formula mass = 96.09 g/mol
Next, we can calculate the ratio of the molar mass of caffeine to the empirical formula mass:
Ratio = Molecular mass / Empirical formula mass
Ratio = 194.19 g/mol / 96.09 g/mol
Ratio = 2.02
This ratio tells us that the molecular formula of caffeine is approximate twice the size of the empirical formula. To find the molecular formula, we can multiply the subscripts in the empirical formula by the ratio:
C₄H₅N₂O × 2 = C₈H₁₀N₄O₂
Therefore, the molecular formula of caffeine is C₈H₁₀N₄O₂.
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S8 + 12O2 -------> 8SO3
If you start with 873.2 g of S8 and 859.3 g of O2, what mass of SO3 will be produced?
What is the amount (in mole) of sodium trioxocarbonate (IV) in 5.3g of the compound? (Na2CO3 = 106)
Answer:
To calculate the amount (in mole) of sodium trioxocarbonate (IV) in 5.3g of the compound , you can use the formula:
Amount (in moles) = Mass of substance / Molecular mass
The molecular mass of sodium trioxocarbonate (IV) (Na2CO3) is 106 g/mol, as given in the question. Substituting the values in the formula, we get:
Amount (in moles) = 5.3 g / 106 g/mol = 0.05 mol
Therefore, the amount (in mole) of sodium trioxocarbonate (IV) in 5.3g of the compound is 0.05 mol.
Note that the given molecular mass of Na2CO3 must be used to obtain the correct answe12 .
Explanation:
in diagram A, what is the value of ^H
The value of h in the right triangle is 7.7 cm.
Why is this so?Trigonometric ratio is used to show the relationship between the sides and angles of a right angled triangle.
In the right triangle, using trigonometric ratio:
a) sin(31) = h/15
⇒ 0.515 = h/15
Making H the subject of the formula we have:
0.515 x 15 = h/15 x 15
h = 7.725
h [tex]\approx[/tex] 7,7
Hence, is is correct to state that the value of h in the diagram is 7.7 cm approximately. See the attached image.
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Full Question:
Although part of your question is missing, you might be referring to this full question:
the diagram shows a right-angled triangle. what is the value of h? give your answer correct to 1 decimal place.
Combustion analysis of a 6.8253 g sample of an unknown organic compound produces 18.520 gof COzand 3.7905 gofH2O. The molar mass of the compound is 324.38 g/mol.Calculate the number of grams of C, H, and O in the original sample.
I need help understanding how to do this, please. (50 points)
Using the determined equivalence point from question 2 and the balanced reaction of acetic acid and sodium hydroxide, calculate the molarity of the acetic acid in your hot sauce packet.
=Equivalence point= (7.46, 7.0)
=Mass of hot sauce (g)= 0.5 g
=Concentration of NaOH solution used (M)= 1 M
=Volume of NaOH solution used to neutralize the sauce (found by locating the equivalence point on the titration graph) (mL)= 7 mL
=pH of NaOH= 10.66
Molarity of a solution is an important method to calculate the concentration of a solution. The concentration of a solution can also be expressed by using another methods like normality, molality, etc. The molarity of acetic acid is
Molarity is defined as the number of moles of the solute present per litre of the solution.
Here 1 mole of acetic acid reacts with 1 mole of NaOH
Moles of NaOH is:
7 mL = 7 x 10⁻³L ₓ (1 mol / L) = 0.007 moles of NaOH = moles of CH₃COOH.
you can assume its density as 1g/mL. Thus, volume of 0.5 g of hot sauce is 0.5 mL = 5 x 10⁻⁴L
And molarity of the packet is:
0.007 moles acetic acid / 5 x 10⁻⁴L = 14 × 10⁻⁷ M
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Hydrogen bonding activity drawings
Answer:UIHIU
A small amount of chemical splashes in Frank’s eye. What should Frank do immediately?
Explanation:A small amount of chemical splashes in Frank’s eye. What should Frank do immediately?
Heat absorbed or released by a substance can be calculated with the equation _____________.
q = m × Cs × ∆T
q = m × Cs ÷ ∆T
q = m + Cs + ∆T
q = m + Cs
Which of the following solutions can function as a buffer
All of the solutions can function as a buffer and the correct option is option 4.
A buffer solution is a water solvent-based solution which consists of a mixture containing a weak acid and the conjugate base of the weak acid or a weak base and the conjugate acid of the weak base.
They resist a change in pH upon dilution or upon the addition of small amounts of acid/alkali to them.
All of these solutions are combinations of weak acid or base with its salt and thus can function as a buffer.
Thus, the ideal selection is option 4.
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please can someone fill the blanks, and/or tell me if this information SO FAR is accurate
it's just about pH levels, bases and acids
The acid base indicators or neutralization indicators are the substances which are employed for the visual detection of the end point in acid base titrations on account of their ability to change colour during the pH change that occurs in vicinity of the end point.
The characteristic pH range in which an acid-base indicator changes colour is called the colour change interval. This varies widely with different indicators. For water pH = 7, acidic solution has pH < 7 and basic solution has pH > 7.
The correct order of pH is:
13 > 10 > 9 > 6 > 4 > 3
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N₂ +
H₂O →>>
NH, -
+
0₂
The balanced chemical equation for the reaction is:
N₂ + 3H₂O → 2NH₃ + O₂
The equation shows that nitrogen gas (N₂) and water (H₂O) react to form ammonia (NH₃) and oxygen gas (O₂). The coefficients in the balanced equation indicate that one molecule of N₂ reacts with three molecules of H₂O to produce two molecules of NH₃ and one molecule of O₂.
1. (16 points) Shown below are IR and MS data for a compound with a molecular formula of C3H₂O
a) Identify the functional groups
responsible for the labeled
absorptions in the IR spectrum.
i) 1601 cm¹
ii) 1691 cm¹
Relative Intensity
100-
80-
m/z
rel. Intensity
22.6
73.1
105 100.0
120
26.2
$1.0
77.0
50 60
TRATT
100 110 120
1601 cm
1691 cm³
iii) From the parent,
what mass is lost to form
the base peak at m/z =
105?
iv) What is the likely
structure of that
fragment that is lost
to form m/z 105?
70
m/z
v) From the parent, what mass is lost to form the m/z = 77 peak?
Answer:
i) 1601 cm¹ - This absorption is likely from a C=O stretching vibration indicative of an aldehyde or ketone functional group.
ii) 1691 cm¹ - This absorption is likely from an O-H stretching vibration indicative of an alcohol functional group.
iii) From the parent, the mass lost to form the base peak at m/z = 105 is 17 amu.
iv) The likely structure of the fragment that is lost to form m/z 105 is C2H2O.
v) From the parent, the mass lost to form the m/z = 77 peak is 28 amu.
vi) The likely structure of the fragment that is lost to form m/z 77 is C2H3O.
Explanation:
Which of these terms best describe an urban community? Select the two
correct responses..
A. Open country
B. Very few shops and restaurants
C. Well-connected to natural systems
D. High-density human population
E. Tall buildings
SUBMIT
The two terms that best describe an urban community are D) high-density human population and E) tall buildings. Open country is typically associated with rural areas, and well-connected natural systems are often found in areas with lower levels of human activity.
Urban communities are characterized by a high concentration of people living in a relatively small area. This means that the population density in urban areas is significantly higher than in rural areas. This high density of population is what drives the development of tall buildings and other types of urban infrastructure. Urban communities are also characterized by the presence of tall buildings. The tall buildings are built to accommodate the high density of human population in urban areas, as they allow a larger number of people to occupy a smaller area of land.
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Can someone please help? And quickly if you can thank you!
The concept ideal gas equation is used here to determine the number of moles. The ideal gas law is the equation of state of a hypothetical ideal gas. Here the number of moles of gas is 0.17.
The equation which is formed by the combination of Boyle's law, Charles's law and Avogadro's law is called the ideal gas equation. An ideal gas is a theoretical gas composed of a set of randomly moving point particles which interact through elastic collisions.
The ideal gas equation is:
PV = nRT
n = PV / RT
10°C = 283 K
Number of moles is:
n = 1.2 × 3.4 / 0.0821 × 283 = 0.17
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Saccharin (HNC7H4SO3) is a weak acid with pKa = 2.32 at 298 K.
a. Write a hydrolysis equation for the reaction of saccharin with water.
b. Calculate the pH of 0.10 M solution of saccharin.
c. Calculate the %ionization of the acid in this solution.
The pka or molarity of a solution may be used to calculate its pH. The saccharin solution in this area has a pH of 1.65.
The pH for a solution determines how acidic or basic it is. It refers to the opposite of the positive logarithm of the H+ ion concentration in maths. A solution that is acidic has a pH below 7, while a basic solution has a pH above 7.
Ka of an acid = [A-] [H+] / [HA]
ka = antilog (-pka)
= antilog (- 2.32)
= 0.0047
Ka = [H+]²/[HA]
[H+]² = Ka × [HA]
= 0.0047 × 0.11
= 0.00051
[H+] = 0.022.
pH = -log [H+]
= -log (0.022)
= 1.65
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Simplify (4.64 x 10¹5) + (8 × 10¹2 ) and write the answer in scientific notation.
The numbers (4.64 x [tex]10^{15[/tex]) + (8 × [tex]10^{12[/tex] ) will be simplified as scientific notation as [tex]4.6 X 10^{15[/tex].
To add these two numbers, we need to make sure they have the same exponent. We can convert 8 × [tex]10^{12[/tex] to scientific notation with the same exponent as 4.64 × 10¹5:
8 × [tex]10^{12[/tex] = 0.008 × [tex]10^{15[/tex]
Now we can add the two numbers:
(4.64 × [tex]10^{15[/tex]) + (0.008 × [tex]10^{15[/tex]) = 4.648 × [tex]10^{15[/tex]
Thus, we can simplify this answer by rounding to two significant figures and expressing it in scientific notation: 4.6 × [tex]10^{15[/tex].
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3 CO + Fe₂O3 --->2 Fe + 3 CO2
what is the mole ratio of carbon monoxide reacting to the amount of
carbon dioxide being produced?
Measurements show that the energy of a mixture of gaseous reactants increases by 190 kJ during a certain chemical reaction, which is carried out at a constant pressure. Furthermore, by carefully monitoring the volume change it is determined easurements show that the energy of a mixture of gaseous reactants increases by during a certain chemical reaction, which is carried out at a constant pressure. Furthermore, by carefully monitoring the volume change it is determined that 143kJ of work is done on the mixture during the reaction.that of work is done on the mixture during the reaction.
The enthalpy or heat content of a system can be defined as the sum of the internal energy and the pressure volume energy of the system. It is denoted by H. The energy change of mixture is 47 kJ.
The transference of energy may take place in the form of work if the system and surroundings have different pressures. According to international conventions, work done on the system is positive and work done by the system is negative.
The enthalpy change is:
ΔH = ΔU + PΔV
190 = ΔU + 143
ΔU = 47 kJ
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the upstairs in a house is usually warmer than downstairs. this is to to this type of heat transfer
Convection currents. Convection currents. allow hot air balloons to rise and explain why it is generally hotter upstairs than downstairs in dwellings.
What is heat transfer?Heat transfer is a thermal engineering subject that deals with the generation, consumption, conversion, and exchange of thermal energy between physical systems.
Heat transmission is categorized into several methods, including thermal conduction, thermal convection, thermal radiation, and energy transfer via phase shifts.
The Transfer of Heat Energy
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Which statement explains why germanium is a semiconductor while titanium
is a conductor?
O A. Titanium atoms have more electrons than germanium atoms.
OB. Germanium atoms have more electrons than titanium atoms.
C. Both elements allow electrons to move between atoms, but
germanium allows more movement of electrons than titanium
does.
O D. Both elements allow electrons to move between atoms, but
titanium allows more movement of electrons than germanium
does.
Answer:
B) Germanium atoms have more electrons than titanium atoms
Explanation:
Trust me I did this but for those who are hesitant
---> Conductors : It is a type of substance which conduct electricity that means it allow the electrons to flow through them.
Example of conductors are, iron, aluminium, gold, etc.
Insulators : It is a type of substance which does not conduct electricity that means it does not allow the electrons to flow through them.
Examples of insulators are, glass, rubber, ceramics, etc.
Semiconductors : It is a type of substance which conduct electricity under certain conditions that means it allow the electrons to flow through them. The conductivity level of semiconductors lie between the conductors and the insulators.
The good examples of semiconductors are silicon, germanium, gallium, and selenium.
In the given options, aluminium, gold are the metals which conduct electricity and concrete is an insulator which do not conduct electricity while the germanium is the good semiconductor.
5. Aspirin (acetylsalicylic acid, HAsp, Mr-180.2) is absorbed from stomach with the form of free
acid. A patient takes some antacid to adjust the pH of gastric juice to 2.95, then takes0.65 g of aspirin.
Assume aspirin dissolves immediately, and the pH of gastric juice is invariant. What is the mass of aspirin that the patient can absorb from stomach at once? pK, of acetylsalicylic acid is 3.48.
CAnswer m= 0.50
The patient's stomach can absorb 0.50 g of aspirin at once.
How to determine mass?The equation for the dissociation of acetylsalicylic acid is:
HAsp ⇌ H+ + Asp-
The dissociation constant (Ka) can be calculated from the pKa value as:
Ka = 10^(-pKa)
Ka = 10^(-3.48) = 2.51 x 10⁻⁴
At pH 2.95, the concentration of H+ ions can be calculated from the equation:
pH = -log[H+]
[H+] = 10^(-pH) = 1.13 x 10⁻³ M
The concentration of Asp- ions can be calculated from the equation:
Ka = [H+][Asp-]/[HAsp]
[Asp-] = Ka[HAsp]/[H+]
[Asp-] = (2.51 x 10⁻⁴)(0.65 g / 180.2 g/mol) / (1.13 x 10⁻³ M)
[Asp-] = 0.0036 M
The total amount of aspirin that can be absorbed is the sum of the amounts of HAsp and Asp-:
m = (0.65 g / 180.2 g/mol) + (0.0036 M)(0.1 L)(180.2 g/mol)
m = 0.50 g
Therefore, the patient can absorb 0.50 g of aspirin from the stomach at once.
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A soft drink contains 33g of sugar in 349g of H2O. What is the concentration of sugar in the soft drink in mass percent?
.
A soft drink contains 33g of sugar in 349g of H[tex]_2[/tex]O. 14.3% is the concentration of sugar in the soft drink in mass percent.
One approach to indicate the concentration of any dissolved component in a solution is by mass percentage. Mass percentage is the ratio of the total weight of a compound in a solution to the overall mass of the solution, expressed in percentages.
In order to express the mass percent of a solution, the grammes of solute are divided by the grammes of solution, and the result is multiplied by 100. As long as you use a comparable number for both the component and solute mass.
Mass percent = (mass of solute/mass of solute+ mass of solvent)×100
= ( 33/ 33+ 349)×100
=14.3%
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A student's sample of Alka Seltzer (0.350 g) contained 0.207 g of sodium bicarbonate (NaHCO3). How many moles of NaHCO3 are in their sample?
Group of answer choices
The number of moles of the sodium bicarbonate is 0.0025 moles
What is the number of moles?We know that the moles is the amount of the substance that is contained and that we can get the moles as the ratio of the mass to the molar mass of the substance and that is what we are going to do in the case of the sodium bicarbonate that we have in the question that is here.
Now we have from the question that;
Mass of the sodium bicarbonate = 0.207 g
Number of moles of the sodium bicarbonate can now be gotten in this case by the use of the formula;
Number of moles
0.207 g/84 g/mol
= 0.0025 moles
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Question 3 of 10
How can the effect of heat on a reaction be determined?
A. Heat will increase reaction rate, but not equilibrium position.
B. Heat always shifts a reaction toward reactant formation.
C. Heat always shifts a reaction toward product formation.
D. Heat is treated as a reactant or a product.
SUBMIT
A saturated solution of a salt was made by adding 36.00 g to 150.0 g water. There was 5.00 g of salt on the bottom that didn't dissolve. What is the % solubility of the salt ?
Answer:
The mass of the salt that dissolved is:
36.00 g - 5.00 g = 31.00 g
The % solubility of the salt can be calculated using the formula:
% solubility = (mass of solute dissolved ÷ mass of saturated solution) × 100%
The mass of the saturated solution is:
36.00 g + 150.0 g = 186.00 g
Therefore, the % solubility of the salt is:
(31.00 g ÷ 186.00 g) × 100% = 16.67%
The % solubility of the salt is 16.67%.
Explanation:
Which compound represents fe+3 o-2
Answer:
The compound that represents Fe+3 O-2 is Fe2O3 (iron oxide or rust)
Calculate the percent ionization of 0.115 M lactic acid in a solution containing 7.0×10−3 M sodium lactate.
The percent ionization of 0.115 M lactic acid in a solution containing 7.0×[tex]10^-^3[/tex] M sodium lactate is 1.22% as percent ionization of a weak acid in solution is a measure of how much of the acid has dissociated into its ions.
The chemical equation for the dissociation of lactic acid is:
HC₃H₅O₃ ⇌ H+ + C₃H₅O₃−
The Ka value for lactic acid is 1.4×10^−4 at 25°C.
Initial: [HC₃H₅O₃]] = 0.115 M, [NaC₃H₅O₃] = 7.0×[tex]10^-^3[/tex] M, [H+] = 0 M, [C₃H₅O₃−] = 0 M
Using the Ka expression for lactic acid,
Ka = [H+][C₃H₅O₃−]/[HC₃H₅O₃]]
Substituting the equilibrium concentrations into the equation and solving for x,
1.4×[tex]10^-^4[/tex]= [tex]x^2[/tex]/(0.115−x)
Solving for x using the quadratic formula,
x =1.4×[tex]10^-^3[/tex] M
Now the percent ionization of lactic acid:
% Ionization = [H+]/[HC₃H₅O₃] × 100%
% Ionization = (1.4×[tex]10^-^3[/tex] M)/(0.115 M) × 100%
% Ionization = 1.22%
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Given the following equations and H° values, determine the heat of reaction at 298 K for the reaction: C(s) + 2 H2(g) -> CH4(g)
H2 (g) + 1/2 02 (g) -> H20 (l)
CO2 (g) + 2 H20 (l) -> CH4 (g) + 2 02 (g)
C(s) + O2(g) -›CO2(g)
H kJ = - 393.5
H kJ = -285.8
H kJ = +890.3
The heat of reaction for the reaction C(s) + 2 H2(g) -> CH4(g) at 298 K can be calculated by using the following equation: ΔH = (ΔHf products - ΔHf reactants).
Applying this equation to the given reaction, we get ΔH = (-890.3 + 393.5 + 285.8) kJ = -210.0 kJ.
This is the heat of reaction at 298 K for the reaction C(s) + 2 H2(g) -> CH4(g).
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Which structural formula represents a non polar symmetrical molecule?
The structural formula which represents a nonpolar symmetrical molecule is CH₄ (methane). Option 2 is correct.
Methane is a tetrahedral molecule with four hydrogen atoms surrounding a central carbon atom. Each hydrogen atom is bonded to the carbon atom by a single covalent bond, and all four hydrogen atoms are arranged symmetrically around the carbon atom, resulting in a nonpolar molecule.
On the other hand, NH₄ (ammonium ion) and H₂O (water) are polar molecules. NH₄ has a positive charge on the nitrogen atom, and the hydrogen atoms are arranged tetrahedrally around it, making it a polar molecule. H₂O has a bent or V-shaped molecular geometry with two lone pairs of electrons on the oxygen atom, resulting in an uneven distribution of charge and making it a polar molecule as well.
Hence, 2. is the correct option.
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Assuming that the mass defect originates solely from the interactions of protons and neutrons in the nucleu, estimate the nuclear binding energy of Li given yhe following data.observee atomic mass (a.m.u) of Li is 7.01600u
1u=1.66054×10^-27kg
Electron rest mass= 9.10939×10^-31kg
Proton rest mass=1.67262×10^-27kg
Neutron rest mass=1.67493×10^-27kg
C=2.998×10^8
The mass lost in the formation of a nucleus is converted into energy in accordance with the Einstein's mass energy relationship and released, thereby tending to impart stability to the nucleus.
An input of the same amount of energy referred to as the binding energy would be required to decompose the nucleus into its component nucleons. So the energy released from the nucleons during the formation of a nucleus is called the binding energy.
No: of protons in 'Li' = 3
No: of neutrons in 'Li' = 4
Total mass of nucleons = 3(1.67262×10⁻²⁷) + 4 (1.67493×10⁻²⁷) = 1.171 × 10⁻²⁶ kg
Mass defect = 1.171 × 10⁻²⁶ - 1.165 × 10⁻⁻²⁶ = 6 × 10⁻²⁹
Binding energy = Δmc² = 6 × 10⁻²⁹ × (2.998×10⁸)² = 5.392 × 10⁻¹² J
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