Answer:
A = 65.46 u
Explanation:
Given that,
The composition of zinc is as follows :
Zn-64 = 48.63%
Zn-66 = 27.90%
Zn-67 = 4.10%
Zn-68 = 18.75%
Zn-70 = .62%
We need to find the average atomic mass of the given element. It can be solved as follows :
[tex]A=\dfrac{48.63\times 64+27.90\times 66+4.1\times 67+18.75\times 68+0.62\times 70}{100}\\A=65.46\ u[/tex]
So, the average atomic mass of zinc is 65.46 u.
A student dissolves 12.6g of amonium nitrate(NH4NO3) in 250.g of water in a well-insulated open cup. She then observed the temperature of the water fall from 23.0°C to 18°C over the course of 6.1 minutes.
NH4NO3 â NH4+ (aq) + NO3^-(aq)
a. Is this reaction exothermic, endothermic, or neither?
b. If you said the reaction was exothermic or calculate the amount of heat that was released or absorbed by the reaction in this case.
c. Calculate the reaction enthalpy ÎHrxn per mole of NH4NO3.
Answer:
a. Endothermic.
b. [tex]Q_{rxn}=5493.6J[/tex]
c. [tex]\Delta H_{rxn}=35.0kJ/mol[/tex]
Explanation:
Hello there!
In this case, according to the given information for this calorimetry problem, it turns out possible for us to proceed as follows:
a. Due to the fact that the temperature of water goes from 23.0 °C to 18.0 °C, we infer this reaction is endothermic as the ammonium nitrate absorbed heat from the water.
b. Here, we consider the following heat equation:
[tex]Q_{rxn}=-Q_{water}[/tex]
Whereas we solve for the heat of reaction by means of the mass of the solution (both water and ammonium nitrate), the specific heat of the solution (we assume it is equal to that of water) and the temperature change:
[tex]Q_{rxn}=-m_{solution}C_{solution}(T_f-T_i)\\\\Q_{rxn}=-(12.6g+250.g)(4.184\frac{J}{g\°C} )(18.0\°C-23.0\°C)\\\\Q_{rxn}=5493.6J[/tex]
c. Here, we divide the previously calculated heat by the moles of ammonium nitrate (molar mass = 80.043 g/mol) to obtain the enthalpy of reaction per mole of this compound:
[tex]n_{NH_4NO_3}=12.6g*\frac{1mol}{80.043 g}=0.157mol\\\\\Delta H_{rxn}=\frac{5493.6J}{0.157mol} =34898.7J/mol\\\\\Delta H_{rxn}=35.0kJ/mol[/tex]
Regards!
An atom's first 2 energy levels are filled and there are 2 electrons in the third energy
level. It's atomic number is:
Answer:
12
Explanation:
2+8+2=12
atomic no is the No of protons
Answer:
Atomic number is 12.
Explanation:
Atomic number = electrons in filled shells + outermost electrons
= 2 + 8 +2
= 12
A reaction vessel for synthesizing ammonia by reacting nitrogen and hydrogen is charged with 6.54 kg of H2 and excess N2. A total of 30.4 kg of NH3 are produced. What is the percent yield of the reaction
Explanation:
The given data is:
The mass of hydrogen is 6.54 kg.
The actual yield is 30.4 kg.
The balanced chemical equation of the reaction is:
[tex]N_2(g)+3H_2(g)<=>2NH_3(g)[/tex]
At first the theoretical yield should be calculated by using the balanced chemical equation:
3 mol. of hydrogen forms ---- 2 mol. of ammonia.
The molar mass of hydrogen is 2.0 g/mol.
The molar mass of ammonia is 17.0 g/mol.
Hence, the above statement can be rewritten as:
6g of hydrogen forms --- 34g of ammonia.
Then,
6.54g of hydrogen forms :
[tex]6.54 kg x 34 g / 6 g\\=37.1 kg[/tex]
% yield = (actual yield /theoretical yield )x 100
=(30.4 kg /37.1 kg )x100
=81.9
Hence, % yield is 81.9.
A 10.53 mol sample of krypton gas is maintained in a 0.8006 L container at 299.8 K. What is the pressure in atm calculated using the
van der Waals' equation for Kr gas under these conditions? For Kr, a = 2.318 L'atm/mol and b = 3.978x10²L/mol.
Answer:
-401.06 atm
Explanation:
Applying,
P = (nRT/V-nb)-(an²/V²)............... Equation 1
Where P = Pressure, R = Universal gas constant, V = molar Volume, T = Temperature in Kelvin, a = gas constant a , b = gas constant b, n = numbers of mole
From the question,
Given: T = 299.8 K, V = 0.8006 L, a = 2.318 L.atm/mol, b = 3.978×10²L/mol
Constant: R = 0.0082 atm.dm³/K.mol
Substitute these values into equation 1
P = [(0.0082×299.8×10.53)/(0.8006-(10.53×397.8)]-[(10.53²×2.318/0.8006²)]
P = (25.89/-4188.0334)-(400.995)
P = -0.0618-400.995
P = -401.06 atm
Complete the sentences by identifying the correct missing words. Alph and beta particles originate from the Choose... . Protection from radiation is necessary because if radiation passes through the body it can damage Choose... . Exposure to radiation can be limited by increasing the Choose... from the radioactive source.
Answer:
Alpha and beta particles originate from the nucleus, protection from radiation is important because if the radiation passes through the body it can damage cells. Exposure to radiation is often limited by increasing the distance from the radioactive source.
Explanation:
Alpha and beta particles come from unstable atoms during their decay. This radiation is extremely harmful which may damage DNA, causing a high rate of mutation. If we increase the distance of the source of radioactive exposure we will prevent damage.The number of organic compounds that have been reported in 2019 is more than 10 million. This is due to carbon's ability to bond to other carbon molecules, called
electron affinity.
ionic bonding.
catenation.
electronegativity.
Answer:
catenation
Explanation:
Carbon atoms have four electrons to share in bonding environments to get to the ideal octet. To do this, it bonds with other carbon molecules, called catenation. Catenation is the ability of an atom to bond and share electrons with other atoms of its kind.
Buffer solutions that maintain certain levels of pH or acidity are widely used in biochemical experiments. One common buffer system uses sodium dihydrogenphosphate and sodium monohydrogenphosphate. What are the formulas of these two compounds
Answer:
Sodium dihydrogenphosphate = NaH₂PO₄
Sodium monohydrogenphosphate = Na₂HPO₄
Explanation:
A buffer solution is a solution is a solution that resists changes to its oH when a little quantity of strong acid or strong base is added to it.
They are solutions of weak acids or weak bases and their salts known as conjugate base or conjugate acids respectively for the weak acids and weak bases.
For example, a solution of the weak acid ethanoic acid and its salt or conjugate base, sodium ethanoate serves as a buffer solution.
In biochemical experiments, where the pH of the reaction medium is kept as constant and as close as possible to that of the internal environment, buffer solutions are widely used. One of the commonly used buffers is the phosphate buffer. The phosphate buffer consists of the acid salts sodium dihydrogenphosphate and sodium monohydrogenphosphate. Sodium dihydrogenphosphate serves as the weak acid while sodium monohydrogenphosphate serves as the conjugate base.
The formulas of these two compounds are given below:
Sodium dihydrogenphosphate = NaH₂PO₄
Sodium monohydrogenphosphate = Na₂HPO₄
12 grams of carbon is burnt with a certain amount of air containing 36 grams of oxygen. The product contains 24 grams of Co, and 4 grams of CO. Calculate the percentage of excess oxygen.
Answer:
C
Oxygen gas is limiting.
C(s) + O
2
→CO
2
(g)
No. of moles of carbon =
12
36
=3 moles
No. of moles of oxygen =
32
32
=1 moles
So, 2 moles of carbon is left and oxygen will be completed.
So, O
2
is limiting reagent.
Answer:
14.5
Explanation:
not sure how I got it but I hope this helped!
milk has a pH of 6.0 and household ammonia has a pH of 12.0. How much more acidic is milk than ammonia
60 I think bcz if there is 1&2 they differ 10 times
The milk has a pH of 6.0 and household ammonia has a pH of 12.0. then milk will be 6 times milk acidic than ammonia.
What is pH?The pH scale, which previously stood for "potential of hydrogen," would be used to describe how acidic or basic an aqueous solution is.
What is an acidic solution?More hydrogen ions are present in an acidic solution than it was in pure water.
It is given then,
[tex](milk)pH_{1} = 6\\(ammonia)pH_{2} = 12[/tex]
The concentration of hydrogen ions can be calculated by using the formula:
[tex][H^{+}] = 10^{-pH}[/tex]
By putting the value of given data in the above equation.
[tex][H^{+}_{milk} ] / H^{+}_{ammonia}= 10^{-6}/10^{-12}\\ = 10^{6} = 6[/tex]
We get that, milk will be 6 times more acidic than ammonia.
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How many shapes contains the same text: KTKEIHLPEQMKJAPDEK
In this figure, four shapes contains the same text as in the red oval. The text given in the red oval is KTKEIHLPEQMKJAPDEK.
What is shape?Shape is "the form of an object or its outline, outer boundary or outer surface".
What is text?Text is "a collection of words or letters that are understandable by the reader".
What is an oval?Oval is a rounded and slightly elongated outline or shape like that of an egg.
Hence, four shapes contains the same text as in the red oval.
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How can beta particles be dangerous to living cells?
A. They move fast and penetrate the skin.
B. They are very high in energy and can travel through most
materials.
C. They move slowly but are very large.
D. They are very low in energy but remain in the body for a long time.
What is the trend in electropositivity in group 1 elements?
Answer:
Electro positivity increases down the group
4. A balloon is filled with 3.0 L of helium at 310 K. The balloon is placed in an oven where the
temperature reaches 340 K. What is the new volume of the balloon?
Answer:
3,29L
Explanation:
3.29L = V2
Formula: V1/T1 = V2/T2
--------------------
Given:
V1 = 3.0 L V2 = ?
T1 = 310 K T2 = 340 K
--------------------
Plugin:
(X stands in place of V2 just to make it easier to look at)
[3.0L / 310K = X / 340K]
(3.0L / 310K = 0.01L/K)
0.01L/K = X / 340K
(multiply 340K on both sides, it cancels out on the right)
0.01L/K * 340K = X
(0.01L/K * 340K = 3.29L)
**3.29L = X**
[or]
**3.29L = V2**
What is the maximum most that can be extracted from 76 g og Cr2O3.
A) 36 g
B) 52 g
C) 104 g
D) 152 g
Answer:
D) 152 g
Explanation:
a mass of 1 mol Cr2O3 = 2 × 52 + 3 × 16 = 152 g number of moles of Cr2O3.
A new member of your team is visually impaired. He's having a hard time reading his computer screen. How can you show that you value diversity? a) Suggest the organization may not be a great fit. O b) Tell him to apply for a different job within the organization that does not b) require computer usage. 12 Od Tell him that he might want to schedule an eye exam. c) d) Provide access to technology that can magnify or read what is on the computer screen.
Answer:
C
Explanation:
If he can't read his computer screen. Means his eyes have problem
A new member of your team is visually impaired. He's having a hard time reading his computer screen. value diversity require computer usage. 12 Tell him that he might want to schedule an eye exam. Therefore, option C is correct.
What is value diversity ?Institutions and community members who value diversity do so in order to recognize the advantages of both their differences and commonalities. They make a deliberate effort to forge enduring connections between individuals and organizations with a broad membership.
When people's unique qualities, abilities, interests, and viewpoints are recognized and supported, they develop a stronger sense of self and health and achieve better results in their academic and professional endeavors.
Although diversity and inclusion are related ideas, they are not the same thing. Diversity has to do with representation or how something is put together. The degree to which the contributions, presence, and viewpoints of other groups of individuals are appreciated and incorporated into a setting is referred to as inclusion.
Thus, option C is correct.
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What happens as energy from sun warms the earth unevenly?
Answer:
Solar heating of the Earth's surface is uneven because land heats faster than water, and this causes air to warm, expand and rise over land while it cools and sinks over the cooler water surfaces.This differential heating is passed on to the air above by conduction which causes air expansion and changes in pressure.
When cyclopentane undergo free-radical substitution with bromine (Br2 /Heat) the product:
a. Bromo cyclopentene
b. Bromo cyclopentane + HBr
c. Bromo cyclopentene + HBr
Explanation:
b. Bromo cyclopentane + HBr
what happened when potassium chloride is added to silver nitrate solutions . there no reaction B two soluble salts are formed C two insoluble salts are formed D. one soluble salts and one insoluble salts are formed.
Answer:
D. One soluble and one insoluble salts are formed
Explanation:
what is the net charge of an ion that as 14 protons 16 electrons and 12 neutrons
Answer:
[tex]\boxed {\boxed {\sf -2}}[/tex]
Explanation:
We are asked to find the net charge of an ion.
The ion has 14 protons, 16 electrons, and 12 neutrons. Recall the charges of each subatomic particle.
Proton: +1 Electron: -1 Neutron: 0Neutrons are neutral and have no charge, so we can ignore them while finding the net charge. There are 14 protons and 16 electrons.
14 protons and 14 electrons have a net charge of 0 because the charges balance each other out. However, we have 16 electrons, which is 2 more than 14. Each electron has a charge of -1, so the 2 electrons add a charge of -2.
The net charge of the ion is -2.
How many grams of Br are in 445 g CaBr2 ?
Explanation:
The mass of bromine is 79.904, and since there are two of them in the Calcium Bromide molecule, we'll multiply it by 2 to get 159.808. Dividing that by the full mass of the molecule then multiply it by 100 will give you the answer.
Which one of the following compounds
contains ionic bonds?
a) NI3
B) HF
c) SiO2
d) CaO
Your answer is CaO.I hope that my answer helped you..
What is the molarity of a solution made by mixing 75.0 mL of 3.00 M NH₄OH with enough water to give 250. mL of solution?
Please explain and show work.
We know
[tex]\boxed{\Large{\sf M_1V_1=M_2V_2}}[/tex]
[tex]\\ \Large\sf\longmapsto M_2=\dfrac{M_1V_1}{V_2}[/tex]
[tex]\\ \Large\sf\longmapsto M_2=\dfrac{3(75)}{250}[/tex]
[tex]\\ \Large\sf\longmapsto M_2=\dfrac{225}{250}[/tex]
[tex]\\ \Large\sf\longmapsto M_2=0.9M[/tex]
Answer:
Mass 1=3M
Mass 2=?
Volume1=75mL
Volume2=250mL
By using molarity formula:
mass1*volume 1=mass2*volume 2
3M*75=mass2*250
mass2=225/250
mass2:0.9M
the molarity of a solution is 0.9M.When (R)-2-chloro-3-methylbutane is treated with potassium tert-butoxide, a monosubstituted alkene is obtained. When this alkene is treated with HBr, a mixture of products is obtained. Identify all of the expected products.
Answer:
See explanation and image attached
Explanation:
The reaction of (R)-2-chloro-3-methylbutane with potassium tert-butoxide yields a monosubstituted alkene .
Since the base is bulky, the Hoffman product predominates because attack occurs at the less hindered carbon atom to yield the major product as shown.
The alkene reacts with HBr at the secondary carbon atom to yield a carbocation intermediate which is flat and planar. Attack on either face of the carbocation yields a racemic mixture of the (2R) and (2S) products.
Rearrangement of the carbocation to yield a tertiary carbocation gives the 2-bromo-2-methyl butane product as shown in the image attached.
Gu
Magnesium metal is reacted with hydrochloric acid to produce
hydrogen gas. A sample of hydrogen gas is collected over water
in a eudiometer at 28.0°C. The atmospheric pressure is 636
mmHg. Determine the pressure (in atm) of the hydrogen gas
produced
Pressure =
atm
The pressure of hydrogen gas is 607.7 mmHg
According of Dalton's law of Partial pressure, the total pressure of a mixture of gases is the sum of the partial pressures of the individual gases in the mixture.
We can now write;
The for hydrogen collected over water, we have a mixture of hydrogen gas and water vapour.
Total pressure = pressure of hydrogen gas + vapour pressure of water
Pressure of hydrogen gas = Total pressure - vapour pressure of water
Pressure of hydrogen gas = 636 mmHg - 28.3 mmHg
Pressure of hydrogen gas = 607.7 mmHg
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Which type of organic compound is shown below?
A. Carboxylic acid
B. Ester
C. Amine
D. Alcohol
Answer:
I think its A maybe am not sure
The Lewis dot model of a molecule is shown.
Based on the model, which of the following is true?
Each carbon has three lone pairs of electrons on it.
The octet of carbon atom remains incomplete in the molecule.
The two carbon atoms share a total of six electrons with each other.
The difference between the electronegativity of carbon and hydrogen is greater than 1.7.
Answer:
The two carbon atoms share a total of six electrons with each other.
Explanation:
Looking at the structure of the molecule H-C≡C-H as shown in the question, we will notice that there exists a triple bond between the two carbon atoms.
Each bond between the two carbon atoms represents two electrons shared. Since there are three bonds between the two carbon atoms, then a total of six electrons were shared between the two carbon atoms hence the answer chosen above.
Complete the following nuclear equations. I recommend filling in the atomic number below each symbol. Instead of using superscripts in our answers, put each answer in the corresponding box. A). 54Fe 4He --> 2 1n _____
Answer:
gamma ray
Explanation:
According to the Vaporization Heat table, the heat needed for 1 mol of H2O to evaporate at 100°C is 40.7KJ and 44.0KJ/mol is needed to evaporate H2O at 25°C. Thus 44.0-40.7=3.7KJ is the energy needed to heat H2O to 100°C from 25°C.
However, according to the heat capacity of H2O, 3.7KJ will only warm the water by ~+43°C, which is not enough to reach 100°C starting from 25°C!
Am I missing something?!
Suppose you have a material in it's liquid phase. As you give energy to that liquid, the temperature of the liquid will increase gradually, and the relation between the increase of temperature and the given energy is the specific heat.
Now, there is a point, a critical point, where the temperature stops to increase, which means that we are near a change of phase. So from this point on, the energy is not used to increase the kinetic energy of the particles (which would increase the temperature), the energy is used to break the bonds and allow a change of phase, for example, from liquid to gas.
So, we know that if you have a mol of water at 100°C, then you need to add 40.7 kJ of energy to change the phase of the water from liquid to gas phase.
This means that if you have a mol of water and you give that exact energy, the temperature will not change, instead, you now will have a mol of water at the temperature of 100°C.
Similarly with the case at 25°C (which happens for a particular pressure only)
So the heat of vaporization can not really be related to increases in temperature as you thought.
For changes in temperature, you need to use the specific heat.
We know that for water it is:
c = 4.184 J/g*°C = 76.15 J/mol*°C
So, if you want to increase the temperature from 25° to 100°
This means an increase of 75°C of one mol of water.
We just need to multiply the above number by:
1mol*(75°C)
Energy needed = (76.15 J/mol*°C)*1mol*(75°C) = 5,711.25 J
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If my primary DNA strand is ATACCGCAA
a write the complimentary DNA strand
Answer:
TATGGCGTT
Explanation:
Complimentary base pairs:
A-T
C-G
Use the other letter for complimentary strands
Consider the reaction: NaNO3(s) + H2SO4(l) NaHSO4(s) + HNO3(g) ΔH° = 21.2 kJ
How much heat must absorbed by the reaction system to convert 100g of NaNO3 into NaHSO4(s)?
Please anyone help me out
Data obtained from the question
NaNO₃ + H₂SO₄ —> NaHSO₄(s) + HNO₃ ΔH° = 21.2 KJ
Heat absorbed by converting 100 g of NaNO₃ =? Step 2Determination of the mass of NaNO₃ that was converted from the balanced equation.
Molar mass of NaNO₃ = 23 + 14 + (16×3)
= 23 + 14 + 48
= 85 g/mol
Mass of NaNO₃ from the balanced equation = 1 × 85 = 85 g
Thus, 85 g of NaNO₃ were converted from the balanced equation.
Step 3Determination of the heat absorbed by converting 100 g of NaNO₃.
From the balanced equation above,
When 85 g of NaNO₃ were converted, 21.2 KJ were absorbed by the system.
Thus, the conversion of 100 g of NaNO₃ will cause the system to absorb = [tex]\frac{100 * 21.2}{85} =[/tex] 24.9 KJ of heat energy.
Therefore, the system will absorb 24.9 KJ of heat energy.
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