Answer:
1. Caffeine, C₈H₁₀N₄O₂
Amount = 1.00/194 = 0.00515 moles
2. Ethanol, C₂H₅OH
Amount = 0.0217 moles
3. Dry Ice, CO₂
amount = 0.0227 moles
Note: The question is incomplete. The compound are as follows:
1. Caffeine, C₈H₁₀N₄O₂;
2. Ethanol, C₂H₅OH;
3. Dry Ice, CO₂
Explanation:
Amount (moles) = mass in grams /molar mass in grams per mole
1. Caffeine, C₈H₁₀N₄O₂
molar mass of caffeine = 194 g/mol
Amount = 1.00 g/194 g/mol = 0.00515 moles
2. Ethanol, C₂H₅OH
molar mass of ethanol = 46 g/mol
Amount = 1.00 g/46 g/mol = 0.0217 moles
3. Dry Ice, CO₂
molar mass of dry ice = 44 g/mol
amount = 1.00 g/44 g/mol = 0.0227 moles
Calculate the wavelength of light (in nm) of the spectral line of Hydrogen where an electron falls from the 6th Bohr orbit to the 3rd Bohr orbit.
a) 540 nm
b) 2000 nm
c) 1090 nm
d) 1050 nm
Answer:
The wavelength of light (in nm) of the spectral line of Hydrogen where an electron falls from the 6th Bohr orbit to the 3rd Bohr orbit is 1090nm
Explanation:
We know that , the wavelength of the light is calculated by Rydberg's formula-
[tex]\frac{1}{\pi} =R^2(\frac{1}{n^2_1} -\frac{1}{n^2_2})[/tex] [tex][n_2>n_1][/tex]
Here , R = Rydberg's constant [tex](1.097\times 10^7 m^-^1)[/tex]
Z = atomic number (for hydrogen , Z= 1)
[tex]n_2 =6 , n_1=3[/tex]
[tex]\pi =[/tex] wavelength of light
Now , putting the values in the Rydberg's formula ,
[tex]\frac{1}{\pi} =1.097\times10^7m^-^1(\frac{1}{3^2} -\frac{1}{6^2} )[/tex]
=[tex]1.097\times 10^7m^-^1 (\frac{4-1}{36} )[/tex]
=[tex]1.097\times 10^7m^-^1(\frac{3}{36} )[/tex]
=[tex]1.097\times 10^7m^-^1(\frac{1}{12} )[/tex]
[tex]\frac{1}{\pi}[/tex] = [tex]0.0914167\times 10^7m^-^1[/tex]
[tex]\pi=\frac{1}{0.0914167\times10^7m^-^1}[/tex]
[tex]\pi=10.9389\times10^-^7\\\pi=1093.89\times10^-^9m[/tex]
=1090nm
Hence , the wavelength of the light is 1090nm,, that is option D is correct.
All organelles that only plant cells have
Answer:
Cell wall, chloroplast, and vacuoles
Explanation:
20 POINTS PLEASE ANSWER ASAP!!!!
Why is calcium (Ca) in group 2, period 4 on the periodic table?
A Calcium, like all group 2 elements, is nonreactive and a gas at room temperature.
B Calcium, like all period 4 elements, is nonreactive and a gas at room temperature,
C Calcium, like all group 2 elements, is reactive and a solid at room temperature.
D. Calcium, like all period 4 elements, is reactive and a solid at room temperature.
Calcium (Ca) is in group 2 and period 4 on the periodic table be because Calcium has 2 valence electrons and 4 electron shell. Thus, calcium is a metal like all other group 2 element.
The correct answer to the question is Option C. Calcium, like all group 2 elements, is reactive and a solid at room temperature.
Calcium is a group 2 element majorly because it has 2 valence electrons. It is also in period 4 because it has 4 electron shells.
Being a group 2 element, calcium is a solid at room temperature and also reactive. All elements in the group 2 are metals.
There are other elements in period 4 which are not solid. For example krypton is an element in period 4 and it is a gas and not reactive.
From the above information, we can conclude that the correct answer to the question is:
Option C. Calcium, like all group 2 elements, is reactive and a solid at room temperature.
See attached image
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the mass number of Fe is 56 . how many neutron are there in a single Fe atom
Answer:
30 neutrons
Explanation:
Since the mass of the iron nuclide is 56 , there must be 56−26=30 neutrons, 30 massive, neutral particles in this iron nucleus.
Which are characteristics of all living things?
Order, sensitivity or response to the environment, reproduction, growth and development, regulation, homeostasis, and energy processing.
Which condition produces an anion?
A. more neutrons than electrons
B. more protons than electrons
C. more electrons than neutrons
D. more electrons than protons
Aspirin is a weak organic acid whose molecular formula is HC9H7O4. An aqueous solution of aspirin is prepared by dissolving 3.60 g/L. The pH of this solution is found to be 2.6. Calculate Ka for aspirin. (atomic mass: C
Answer:
Ka = 3.50x10⁻⁴
Explanation:
First, we need to convert the unit of 3.60 g/L to mol/L:
[tex] C_{C_{9}H_{8}O_{4}} = 3.60 \frac{g}{L}*\frac{1 mol}{180.16 g} = 0.0200 mol/L [/tex]
The reaction dissociation of aspirin in water is:
C₉H₈O₄ + H₂O ⇄ C₉H₇O₄⁻ + H₃O⁺
0.02 - x x x
The constant of the above reaction is:
[tex] Ka = \frac{[C_{9}H_{7}O_{4}^{-}][H_{3}O^{+}]}{[C_{9}H_{8}O_{4}]} [/tex]
[tex] Ka = \frac{x^{2}}{0.02 - x} [/tex]
To find Ka we need to find the value of x. We know that pH = 2.6 so:
[tex] pH = -log[H_{3}O^{+}] [/tex]
[tex] 2.6 = -log(x) [/tex]
[tex] x = 2.51 \cdot 10^{-3} M = [H_{3}O^{+}] = [C_{9}H_{7}O_{4}^{-}] [/tex]
Now, the concentration of C₉H₈O₄ is:
[tex] C_{C_{9}H_{8}O_{4}} = 0.02 - 2.51 \cdot 10^{-3} = 0.018 M [/tex]
Finally, Ka is:
[tex] Ka = \frac{[C_{9}H_{7}O_{4}^{-}][H_{3}O^{+}]}{[C_{9}H_{8}O_{4}]} = \frac{(2.51 \cdot 10^{-3})^{2}}{0.018} = 3.50 \cdot 10^{-4} [/tex]
Therefore, the Ka of aspirin is 3.50x10⁻⁴.
I hope it helps you!
You need to make an aqueous solution of 0.243 M iron(III) chloride for an experiment in lab, using a 125 mL volumetric flask. How much solid iron(III) chloride should you add?
Answer:
5 g
Explanation:
From the question, we have,
Molarity of FeIII solution= 0.245 M
Volume of solution = 125 ml
From
number of moles= concentration × volume
We have;
Number of moles= 0.245 M × 125/1000
Number of moles = 0.031 moles
Molar mass of Fe III = 162.5g/moles
Mass of iron III = number of moles× molar mass = 0.031 × 162.5= 5 g
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A 100.00-mL water sample was adjusted to pH 10 and titrated to the calmagite endpoint with 10.87 mL of 0.0125 M EDTA solution. Then the pH of another 100.00-mL water sample was adjusted to pH 12 and titrated with EDTA to the calcon endpoint. In this second titration, 2.63 mL of titrant was required. Calculate the concentration of Mg2 and Ca2 in the water. Express your answers in mg/L of CaCO3 and MgCO3, respectively.
Answer:
The mass of Ca²⁺ present in the water sample = 13.23 mg/L.
The mass for the Mg²⁺ in the water sample = 25.06 mg/L.
Explanation:
We are given the following set of values which are going to aid in solving this particular question/problem. Thus, the parameters or data or information is given below:
First part:
Total volume of the water sample = 100.00-mL water sample, volume of the EDTA solution = 10.87 mL, the concentration of the EDTA solution = 0.0125 M, the adjusted pH of the water sample with = 10.
Second part:
Total volume of the water sample = 100.00-mL water sample, volume of the EDTA solution = 2.63 mL and the adjusted pH of the water sample with = 12.
Thus, the first thing to do now is to determine the number of moles of the EDTA solution in Ca²⁺ titration which is; 0.0125 x 0.00263 = 3.30 x 10⁻⁵ moles.
The mass of Ca²⁺ present in the water sample = [3.30 x 10⁻⁵ moles × 40.08 ] ÷ 100 mL. = 13.23 mg/L
In 100mL, the number of moles of Mg²⁺ = (total number of moles of EDTA solution used ) - ( number of moles of the EDTA solution in Ca²⁺ titration).
Also, The number of moles of Mg²⁺ = ( 0.0125 x 0.01087) - (3.30 x 10⁻⁵ moles.) = 1.031 x 10⁻⁴ moles.
The mass for the Mg²⁺ in the water sample = 1.031 x 10⁻⁴ moles x 24.305/0.1 = 25.06 mg/L.
Aluminum metal and bromine liquid (red) react violently to make aluminum bromide (white powder). One way to represent this equilibrium is:
Al(s) + 3/2 Br2(l)AlBr3(s)
We could also write this reaction three other ways, listed below. The equilibrium constants for all of the reactions are related. Write the equilibrium constant for each new reaction in terms of K, the equilibrium constant for the reaction above.
1) 2 AlBr3(s) 2 Al(s) + 3 Br2(l)
2) 2 Al(s) + 3 Br2(l) 2 AlBr3(s)
3) AlBr3(s) Al(s) + 3/2 Br2(l)
Answer:
Explanation:
Al(s) + 3/2 Br₂(l) = AlBr₃(s)
K = [ AlBr₃] / [ Al] [ Br₂]³/²
K² = [ AlBr₃]² / [ Al ] ² [ Br₂]³
2 AlBr₃ = 2 Al(s) + 3 Br₂(l) =
K₁ = [ Al ] ² [ Br₂]³ / [ AlBr₃]²
K₁ = ( 1 / K² ) = K⁻²
2 ) 2 Al(s) + 3 Br₂(l) = 2 AlBr₃(s)
K₂ = [ AlBr₃ ]² / [ Al ]² [ Br₂ ]³
K₂ = K²
3 )
AlBr₃(s) = Al(s) + 3/2 Br₂(l)
K₃ = [ Al ] [ Br₂ ] ³/² / [ AlBr₃ ]
= ( 1 / K ) = K⁻¹
Which statements best describe half lives of radioactive isotopes
Answer:
The half-life varies depending on the isotope.
Half-lives range from fractions of a second to billions of years.
The half-life of a particular isotope is constant.
Explanation:
Make sure you add the options
3. A certain Chemical Industry company has a quality control job opening. The job is open for any major with basic knowledge of chemistry. You decided to apply. In the interview the HR personnel gives you a sealed folder from a certain lot to test your laboratory experience, as well as your quantitative and volumetric analysis skills. The chemical contained in the sample is benzoic acid (C-H602) and it is known to be a monoprotic acid. In order to get the job, you need to determine if the sample's purity is acceptable based on their standards. Inside the folder you found a vial with a solid sample labeled BA-I, a periodic table, and the following data: 1.250 g of the sample required 20.15 mL of 0.500 M concentration of NaOH to reach the end point. The lot can be denied if the purity is below 99.5 % purity.
1) What is the purity in the sample?
2) Is it the purity acceptable?
3) Would you repeat the titration experiment?
Answer:
1) 97.6%
2) No the purity is not acceptable because the standard is 99.5% purity.
3) Yes I will repeat the titration experiment to confirm my result.
Explanation:
Equation of the reaction;
C7H6O2(aq) + NaOH(aq) ---------> C7H5ONa(aq) + H2O(aq)
From the information provided;
Number of moles of NaOH reacted = concentration × volume = 20.15/1000 × 0.500 = 0.01 moles
From the reaction equation;
1 mole of C7H6O2 reacts with 1 mole of NaOH
Hence 0.01 moles of C7H6O2 will react with 0.01 moles of NaOH
Mass of C7H6O2 reacted = number of moles of C7H6O2 × molar mass of C7H6O2
Molar mass of C7H6O2 = 122.12 g/mol
Mass of C7H6O2 reacted = 0.01 moles × 122.12 g/mol = 1.22 g
Percentage by mass of pure C7H6O2 in the impure sample = 1.22/1.250 × 100 = 97.6 %
BaCl2+Na3PO4-->NaCl+Ba3 (PO4)2If 3.54g of Ba3 (PO4)2are produce by the reaction given how many grams of the starting material BCl2 were used?a) 3.680 gb) 1.23 gc) 3.68 gd) 4.16 g
Answer:
1.23 g
Explanation:
Given that the mass of barium phosphate formed= 3.54 g
Molar mass of Ba3 (PO4)2 = 602 g/moles
Number of moles of Ba3 (PO4)2= 3.54g/602 g/moles = 0.0059 moles
Since 1 mole of BaCl2 forms 1 mole of Ba3 (PO4)2
Hence, 0.0059 moles of BaCl2 yields 0.0059 moles of Ba3 (PO4)2
Hence mass of BaCl2 reacted= mass × molar mass= 1.23 g
Nicotinic acid, HC6H4NO2, is a B vitamin. It is also a weak acid with Ka = 1.4 × 10-5. Calculate [H+] and the pH of a 0.041 M solution of HC6H4NO2.
Answer:
[H+] = 7.576x10⁻⁴M
pH = 3.12
Explanation:
Based on the equilibrium of the nicotinic acid in water:
HC6H4NO2(aq) + H2O(l) ⇄ C6H4NO2-(aq) + H3O+(aq)
Ka = [C6H4NO2-] [H3O+] / [HC6H4NO2]
As both C6H4NO2-(aq) and H3O+(aq) comes from the same equilibrium, we can approximate their concentration as X and replace:
Ka = [C6H4NO2-] [H3O+] / [HC6H4NO2]
1.4x10⁻⁵ = [X] [X] / [0.041M]
5.47x10⁻⁷ = X²
7.576x10⁻⁴M = X = [H+]And as pH is defined as -log [H⁺]
pH = 3.12A geochemist has determined by measurements that there are moles of tin in a sample of cassiterite. How many moles of oxygen are in the sample
The question is incomplete, the complete question is:
This is the chemical formula for cassiterite (tin ore): SnO2 A geochemist has determined by measurements that there are 13. moles of tin in a sample of cassiterite. How many moles of oxygen are in the sample? Round your answer to 2 significant digits.
Answer:
Explanation:
In SnO2, there are two moles of oxygen for each mole of tin.
Hence, if there are 13 moles of tin, then we should have 13 * 2 moles of oxygen. This gives us 26 moles of oxygen.
Hence there are 26 moles of oxygen.
Suppose the reaction Ca3(PO4)2 + 3H2SO4 → 3CaSO4 + 2H3PO4 is carried out starting with 149 g of Ca3(PO4)2 and 86.9 g of H2SO4. How much phosphoric acid will be produced?
Answer:
57.9 grams .
Explanation:
Ca₃(PO₄)₂ + 3H₂SO₄ → 3CaSO₄ + 2H₃PO₄
1 mole 3 moles 2 moles
149 g of Ca₃(PO₄)₂ = 149 / 310 = .48 moles
86.9 g of H₂SO₄ = 86.9 / 98 = .8867 moles
Here H₂SO₄ is the limiting reagent .
.8867 / 3 = .2955
.2955 moles of Ca₃(PO₄)₂ reacts with .8867 mole of H₂SO₄ to give
2 x .2955 moles of H₃PO₄
H₃PO₄ produced = 2 x .2955 moles
= .591 moles
= .591 x 98 = 57.9 grams .
State the number of sig figs in each value:
1) 0.00004050
2) 54.7000
3) 1,000.09
4) 0.039
Answer:
Explanation:
Significant figure implies number of digits that are to be considered. Some rules are required to be considered when writing a given expression to an expected significant figures.
So that:
1) 0.00004050 is 4 significant figures
2) 54.7000 is 6 significant figures
3) 1,000.09 is 6 significant figures
4) 0.039 is 2 significant figures
The chemical formula for sumuric acid is H Son. In one molecule of sulfuric acid, there are____
A. two atoms of hellum
B. two atoms of oxygen
C. four atoms of oxygen
D. four atoms of sulfur oxide
Answer:
I want to say option C: four atoms of oxygen. Sorry if I'm wrong
Why doesn't chromic acid oxidize tertiary alcohol?
What is the best way to organize desert several several million different types of organisms on earth
Answer:
The desert should be divided into different types based on its properties. The organisms living in specific type of desert should be named accordingly.
Explanation:
There are usually five major types of desert in the world. Tropical, rainy, semi arid desert, coastal desert and dry desert. There are many different types of organisms living in these deserts. The biodiversity has made it difficult for the humans to analyse and identify the millions of different types. The best way is to organize and name the organisms that live in specific types of deserts.
When 60 mL of 0.22 M NH4Cl is added to 60 mL of 0.22 M NH3, relative to the pH of the 0.10 M NH3 solution the pH of the resulting solution will:____________.
Answer:
Will be more acidic
Explanation:
The equilibrium of NH3 in water is:
NH3(aq) + H2O(l) ⇄ NH4⁺(aq) + OH⁻(aq).
Where equilibrium constant, Kb, is:
Kb = 1.85x10⁻⁵ = [NH4⁺] [OH⁻] / [NH3]
From 0.10M NH3, the reaction will produce X of NH4⁺ and X of OH⁻ and Kb will be:
1.85x10⁻⁵ = [X] [X] / [0.10M]
1.8x10⁻⁶ = X²
X = 1.34x10⁻³ = [OH⁻]
As pOH = -log[OH⁻] = 2.87
And as pH = 14 - pOH
pH of the 0.10M NH3 is 11.13
Now, to find the pH of the NH4Cl and NH3 we need to use H-H equation for bases:
pOH = pKb + log [NH4⁺] / [NH3]
Where pKb is -log Kb = 4.74 and [] are moles of both compounds.
Moles of [NH4⁺] = [NH3] = 60mL, 0.060L*0.22M = 0.0132moles:
pOH = 4.74 + log [0.0132] / [0.0132]
pOH = 4.74
pH = 14 - 4.74 = 9.26
That means the pH of the resulting solution will be more acidic
A certain first-order reaction has a rate constant of 2.10×10−2 s−1 at 19 ∘C. What is the value of k at 58 ∘C if Ea = 82.0 kJ/mol ?
Answer:
K₂ = 1.12s⁻¹
Explanation:
Based on Arrhenius equation:
ln K₂/K₁ = -Ea/R (1/T₂ - 1/T₁)
Where K is rate constant,
R is gas constant (8.314J/molK),
T is absolute temperature (In K) Of 1, initial state and 2, final state.
ln K₂/K₁ = -Ea/R (1/T₂ - 1/T₁)
ln K₂/2.10x10⁻²s⁻¹ = -82000J/mol/8.314J/molK (1/(273.15 + 58) - 1/(273.15 + 19))
ln K₂ / 2.10x10⁻²s⁻¹ = 3.976
K₂ / 2.10x10⁻²s⁻¹ = 53.3
K₂ = 1.12s⁻¹
The three dots in the Lewis dot diagram for boron indicates that it. Please help
Answer:
valence electrons
Explanation:
it is outermost shell of electrons
The three dots in the Lewis dot diagram for boron indicates that it has three valence electrons.
The three dots in the Lewis dot diagram for boron indicates that it
can bond with three other atoms. NO. It can bond with less than 3 atoms by forming double or triple bonds.can only form triple covalent bonds. NO. It can also form single and double covalent bonds.has three valence electrons. YES. It has 3 electrons in the outermost electron shell.scores a 3 on Pauling's electronegativity scale. NO. The electronegativity of boron is 2.04.The three dots in the Lewis dot diagram for boron indicates that it has three valence electrons.
You can learn more about the Lewis dot structure here: https://brainly.com/question/20300458
Which of the following is one way creativity can help scientists?
By ensuring they follow the scientific method
By increasing the amount of time it takes to complete scientific experiments
By making sure they only try things that have already been proven
By leading them to ask more questions about the natural world
Answer:
Creativity can help scientists by leading them to ask more questions about the natural world.
Explanation:
Beacause they use creativity to make up questions about the natural world.
A. In a separatory funnel containing ethyl acetate and 10% aqueous sodium bicarbonate (NaHCO3), which layer would contain the brominated aromatic compound?
Answer:
ethyl acetate layer
Explanation:
This question tests your knowledge of the principle of solvent extraction.
In solvent extraction, there is always an organic layer and an aqueous layer. The ethyl acetate is the organic layer while the sodium bicarbonate is the aqueous layer.
A brominated aromatic compound will be extracted into the organic layer (ethyl acetate layer).
Which are replenished MORE quickly than they are used?
A. energy resources
B. material resources
C. renewable resources
D. nonrenewable resources
Answer:c
Explanation: more expensive so people use nonrenewed energy more.
Identify the following reaction as an endothermic reaction, exothermic reaction, or both endothermic and exothermic:
Dissolving NH4Cl in water to make a cold pack.
Answer:
Endothermic reaction
Explanation:
Endothermic reactions are defined as the type of chemical reaction in which the system absorbs the energy from the surroundings and the temperature of the surrounding decreases while in Exothermic reactions, heat is released by the system to the surroundings and it makes the surrounding warm.
The given example is an "endothermic reaction" because the reaction between NH4Cl and water is making the surrounding cool (cold pack) due to the release of heat.
Hence, the correct answer is "endothermic reaction".
1. What step dogs every scientific experiment begin with?
A hypothesis
B. procedures
C conclusion
D. question/problem
The water bottle contains 575 grams of water at 80°C. The water eventually cools to
40°C. How many calories of heat could be transferred to the student's back?
Answer:
–23000 Calories.
NOTE : The negative sign indicates that heat has been loss to the student back.
Explanation:
The following data were obtained from the question:
Mass (M) of water = 575 g
Initial temperature (T1) = 80 °C
Final temperature (T2) = 40 °C
Heat (Q) transferred =.?
Next, we shall determine the change in temperature (ΔT).
This is illustrated below:
Initial temperature (T1) = 80 °C
Final temperature (T2) = 40 °C
Change in temperature (ΔT) =?
Change in temperature (ΔT) = T2 – T1
Change in temperature (ΔT) = 40 – 80
Change in temperature (ΔT) = –40°C
Finally, we shall determine the heat transferred. This can be obtained as follow:
Mass (M) of water = 575 g
Change in temperature (ΔT) = –40°C
Specific heat capacity (C) of water = 1 Cal/g°C
Heat (Q) transferred =.?
Q = MCΔT
Q = 575 × 1 × –40
Q = –23000 Calories
NOTE : The negative sign indicates that heat has been loss to the student back.
Determine ΔH for the reaction CaCO3 → CaO + CO2 given these data: 2 Ca + 2 C + 3 O2 → 2 CaCO3 ΔH = −2,414 kJ C + O2 → CO2 ΔH = −393.5 kJ 2 Ca + O2 → 2 CaO ΔH = −1,270 kJ Write your answer using 4 significant figures, do not include units.
Answer:
The ΔH for the reaction is -456.5 KJ
Explanation:
Here we want to determine ΔH for the reaction;
Mathematically;
ΔH = ΔH(product) - ΔH(reactant)
In the case of the first reaction;
ΔH = ΔH(CaO) + ΔH(CO2) - ΔH(CaCO3) ...........................(*)
From the other reactions, we can get the respective ΔH for the individual molecule in the reaction
In second reaction;
Kindly note that for elements, molecule of gases, ΔH = 0
What this means is that throughout the solution;
ΔH(Ca) = 0 KJ
ΔH(O2) = 0 KJ
ΔH(C) = 0 KJ
Thus, in writing the equation for the subsequent chemical reactions, we shall need to write and equate the overall ΔH for the reaction to that of the product alone
So in the second reaction
ΔH = 2ΔH(CaCO3)
Thus;
-2414/2 = ΔH(CaCO3)
ΔH(CaCO3) = -1,207 KJ
Moving to the third reaction, we have;
ΔH = ΔH(CO2)
Hence ΔH(CO2) = -393.5 KJ
For the last reaction;
ΔH = ΔH(CaO)
Hence ΔH(CaO) = -1270 KJ
Going back to equation *
ΔH = ΔH(CaO) + ΔH(CO2) - ΔH(CaCO3)
Using the values of the ΔH of the respective molecules given above,
ΔH = -1270 + (-393.5) - (-1207)
ΔH = -456.5 KJ
