Answer:
Melting-point apparatus
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!
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:
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
What is the trend in electropositivity in group 1 elements?
Answer:
Electro positivity increases down the group
List the following substances in order of decreasing boiling point:
CO2, Ne, CH3OH, KF
The correct order of the substances in order of decreasing boiling point is,
KF , CH30OH , CO2 , Ne
What is boiling point?Boiling point, the temperature at which the force exerted by the surroundings upon a liquid exists equaled by the pressure exerted by the vapor of the liquid; under this situation, the addition of heat affects the transformation of the liquid into its vapor without increasing the temperature.
The main difference between the boiling point and the melting point stands that the melting point is determined as the temperature at which solid and liquid phases exist in equilibrium, whereas the boiling point stands as the temperature at which the vapor pressure of a liquid stands equal to the external pressure.
Hence, The correct order of the substances in order of decreasing boiling point is,
KF , CH30OH , CO2 , Ne
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2- . the number of waves in n *10 bohr's orbit are
oxide. b) Silicon dio
43. What is the nature of an enzyme?
a) Vitamin. b) Lipid. c) Carbohydrate. d) Protein
44. Name the enzyme which catalyzes the oxidation-reduction reaction?
a) Transaminase. b) Glutamine synthetase. c) Phosphofructokinase. d) Oxidoreductase
nontido
Answer:
43) protein
44) oxidoreductase
.formular for Charles' law
Explanation:
Hey there!
Charles law states that the volume of gas is directly proportional to the absolute temperature at constant pressure.
As the fact is, at a constant pressure the volume of fix amount of dry gas is directly proportional to absolute temperature from Charles law.
Since V and T are directly varying directly, we can write the equation using constant "k".
V/T = k
In this case the value of k depends on the pressure of gas, the amount of gas and also unit volume.
V/T = k .........(i)
Let us consider V1 and T1 the Volume and temperature of the ideal gases.
Then the equation is;
V1/T1 =k........(ii)
After this let change the temperature and volume be T2 and V2, respectively.
Then the equation is:
V2/T2 = k.......(iii)
Now; Equating equation (ii) and (iii)…
V1/T1 = V2/T2
So, this the formula. (i.e V1/T1 = V2/T2).
Hope it helps!
g When 2.50 g of methane (CH4) burns in oxygen, 125 kJ of heat is produced. What is the enthalpy of combustion (in kJ) per mole of methane under these conditions
Answer:
-800 kJ/mol
Explanation:
To solve the problem, we have to express the enthalpy of combustion (ΔHc) in kJ per mole (kJ/mol).
First, we have to calculate the moles of methane (CH₄) there are in 2.50 g of substance. For this, we divide the mass into the molecular weight Mw) of CH₄:
Mw(CH₄) = 12 g/mol C + (1 g/mol H x 4) = 16 g/mol
moles CH₄ = mass CH₄/Mw(CH₄)= 2.50 g/(16 g/mol) = 0.15625 mol CH₄
Now, we divide the heat released into the moles of CH₄ to obtain the enthalpy per mole of CH₄:
ΔHc = heat/mol CH₄ = 125 kJ/(0.15625 mol) = 800 kJ/mol
Therefore, the enthalpy of combustion of methane is -800 kJ/mol (the minus sign indicated that the heat is released).
Provide two real world examples of habitats and niches within ecosystems? Explain the interdependence that exists within those ecosystems.
Answer:
An ecosystem encompasses living organisms and the nonliving elements of their environments. Hence, the components of an ecosystem include animals, plants, microorganisms, rocks, soil, minerals, atmosphere, and the surrounding water masses. An ecosystem can be huge, cutting across several nations, or it can be relatively small, such as the body of an animal, which is home to numerous microorganisms.
We can describe ecosystems under two headings – natural ecosystems and unnatural ecosystems. Unnatural ecosystems, which include agricultural and urban areas, are greatly modified and maintained by human activity. Conversely, natural ecosystems are self-sufficient, balanced ecological units, with a high proportion of native biodiversity and minimal human disruption.
The natural ecosystem is broad. It is divided into two major groups – terrestrial and aquatic ecosystems. These are further divided into many other smaller types of ecosystems as outlined in this article.
Explanation:
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What is molarity?
A. A measure of saturation.
B. A ratio of moles of solvent to moles of solution.
C. A measure of moles.
D. A measure of concentration.
Answer:
Molarity is a measure of concentration
I Hope its right if not so advance sorry :)
The molarity measures the number of moles of the solute present per liter of the solution and it measures the concentration of the solution. option D is correct.
What is molarity?Molarity is the amount or the number of moles present in per liter of the solution it is the unit to measure the concentration of the moles.
Unit of molarity will be moles per liter and the temperature does not affect the molarity of the solution. molarity can be calculated by dividing the concentration of the solution by the molar mass of the given element.
molarity = weight / mass × 1000/ volume in liters.
With the help of this formula, we can calculate the molarity.
Therefore, molarity measures the number of moles of the solute present per liter of the solution and it measures the concentration of the solution. option D is correct.
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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.
Notice
10 January 2018
Gift A Tree
This is to inform students of Class XII to assemble in the ground on Saturday, 31 January
2018 at 8:00 in the morning to participate in a Tree Plantation Ceremony being organised
by the Environment Club as a part of the Farewell Programme.
Amita/Amit
Secretary, Environment Club)
Exercises
As the Head Boy/ Head Girl, Central Public School, draft a notice informing all students about
a wrist watch that was found near the school canteen.answar
Answer:
gahwidsuacsgsuacayau1joagavahiq8wtw8quavakiafabajozyavqhaigavayquata
Explanation:
vahaiqgahiavavqugafayqigqvsbjsiagwyeiwvvs
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..
Place the following elements in order of decreasing atomic size: lead, phosphorus, oxygen, cesium, barium, and silicon.
Rank from largest to smallest. To rank items as equivalent, overlap them.
Cs, O, P, Si, Ba, Pb
Answer:
Cs> Ba> Pb>Si> P>O
Explanation:
Recall that atomic size decreases across a period and increases down the group.
As we move from Cs to Ba, the atomic size decreases across the period. Lead is larger than silicon since atomic size increases down the group.
Between phosphorus and oxygen, phosphorus is larger than oxygen as you move across the period.
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.PLEASE HELP ASAP!!!
Answer:
I don't know What can I do.
In the reaction HCI + NH4OH --> NH4CI+H2O, which compound has an element ratio of 1:4:1?
H2O
NH4Cl
HCI
ΝΗ4ΟΗ
The compound in this reaction which is having the elemental ratio of 1:4:1 is NH₄Cl where nitrogen and chlorine are of one mole each with 4 hydrogens.
What is elemental ratio?Elemental ratio of a compound is the ratio of number of atoms of each elements in that compound. The elemental ratio can be determined from the molecular formula of compounds.
The given reaction is a double displacement reaction. Here, the Cl group is replaced to the ammonia and OH group is replaced to the water. Thus, two species is replaced in the reaction.
In NH₄Cl, there are one nitrogen, 4 hydrogens and one chlorine atom. Therefore, the elemental ratio of the compound is 1:4:1. The elemental ratio of water is 2:1 and HCl is 1:1 and that in NH₄OH is 1:5:1. Hence, option b is correct.
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3. Suppose you wanted to design an experiment to test the composition of a mixture that includes sodium phenoxide (NaC6H5O). You know that this solid mixture contains both the NaC6H5O and some inert NaCl, but do not know how much of each is present. You decide to test the composition by titrating with 0.100-M HCl. a. If a 1.000-g sample is 25% NaC6H5O by mass, how many mL of 0.100-M HCl would be required to reach the equivalence point of the titration
Answer:
21.5mL of a 0.100M HCl are required
Explanation:
The sodium phenoxide reacts with HCl to produce phenol and NaCl in a 1:1 reaction.
To solve this question we need to find the moles of sodium phenoxide. These moles = Moles of HCl required to reach equivalence point and, with the concentration, we can find the needed volume as follows:
Mass NaC6H5O:
1.000g * 25% = 0.250g NaC6H5O
Moles NaC6H5O -116.09g/mol-
0.250g NaC6H5O * (1mol/116.09g) = 2.154x10⁻³ moles = Moles of HCl required
Volume 0.100M HCl:
2.154x10⁻³ moles HCl * (1L/0.100mol) = 0.0215L =
21.5mL of a 0.100M HCl are requiredStibnite, Sb2S3, is a dark gray mineral from which antimony metal is obtained. What is the mass percent of antimony in the sulfide? If you have 1.00 kg of an ore that contains 10.6% antimony, what mass of Sb2S3 (in grams) is in the ore?
Answer:
duw8 Wert gsi
Explanation:
pues pues y 8y1rcuecisscfjfj3eoeu xv cihskdkkd HD jekifeuifkeñ elijo eh fh FC eh SSH DJ djdvheshdhs
The mass percent of antimony in the sulfide is 71.7% and the mass of Sb2S3 is 0.148 g.
What is mass percent?Mass percent is defined as a way of expressing a concentration or describing a component in a particular mixture.
To calculate the mass percent of an element in a compound, divide the mass of the element in 1 mole of the compound by the molar mass of the compound and multiply the result by 100.
Mass percent = Mass of chemical / Total mass of compound x 100
Mass of ore = 10 kg
% antimony in ore = 10.6%
= 10.6 / 100 = 0.106 g
Mass of antimony = 0.106 g
Mass percent = Mass of antimony / Mass of stibnite x 100
71.7% = 0.106 / X x 100
X = 0.106 x 1000 / 71.7 x 1000
= 106 / 717 = 0.148 g
Thus, the mass percent of antimony in the sulfide is 71.7% and the mass of Sb2S3 is 0.148 g.
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What mass of precipitate (in g) is formed when 250.0 mL of 0.150 M CuCl₂ is mixed with excess KOH in the following chemical reaction?
CuCl₂(aq) + 2 KOH(aq) → Cu(OH)₂(s) + 2 KCl(aq)
Answer:
3.6487g
CuCl2 moles reacted = (0.15×250)/1000
according to balanced chemical equation
precipitated Cu(OH)2 moles = Reacted CuCl2 moles
molar mass of Cu(OH)2 = 63.5+ (17+1)×2 = 97.5
mass of precipitate = (97.5 × 0.15×250)/1000
= 3.648g
PLEASE HELP!!
this is on USAtestprep
a)
b)
c)
d)
A sample of an ideal gas is slowly compressed to one-half its original volume with no change in temperature. What happens to the average speed of the molecules in the sample
Answer:
See explanation
Explanation:
The average speed of the molecules of a gas depends on the temperature of the gas and its molar mass and not on the volume of the gas.
The average velocity of a gas is given by; vrms=√3RTM
R= gas constant
T= Absolute temperature
M= molar mass of the gas
Where the temperature of the gas is held constant, the average velocity of gas molecules depends on the molar mass of the gas. Hence, if a sample of gas is slowly compressed to one-half of its original volume with no change in temperature, the average speed of the molecules in the sample of gas remains the same.
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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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
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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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**
Copper crystallizes in a face-centered cubic unit cell. The density of copper is 8.94 g/cm3. Calculate the length of the edge of the unit cell in pm.
a) 461 pm
b) 361 pm
c) 261 pm
d) 161 pm
e) None of the above
Answer:
361.4 pm is the length of the edge of the unit cell
Explanation:
First, let's calculate the average volume each atom is taking. Start with calculating how many moles of copper we have in a cubic centimeter by looking up the atomic weight. Atomic weight copper = 63.546 Now divide the mass by the atomic weight, getting 8.94 g / 63.546 g/mol = 0.140685488 mol And multiply by Avogadro's number to get the number of atoms: 0.140685488 * 6.022140857x10^23 = 8.472278233x10^22 Now examine the face-centered cubic unit cell to see how many atoms worth of space it consumes. There is 1 atom at each of the 8 corners and each of those atoms is shared between 8 unit cells for for a space consumption of 8/8 = 1 atom. And there are 6 faces, each with an atom in the center, each of which is shared between 2 unit cells for a space consumption of 6/2 = 3 atoms. So each unit cell consumes as much space as 4 atoms. Let's divide the number of atoms in that cubic centimeter by 4 to determine the number of unit cells in that volume. 8.472278233x10^22 / 4 = 2.118069558x10^22 Now calculate the volume each unit cell occupies. 1 cm^3 / 2.118069558x10^22 = 4.721280262x10^-23 cm^3 Let's get the cube root to get the length of an edge. (4.721280262x10^-23 cm^3)^(1/3) = 3.61426x10^-08 cm Now let's convert from cm to pm. 3.61426x10^-08 cm / 100 cm/m * 1x10^12 pm/m = 361.4 pm Doing an independent search for the Crystallographic Features of Copper, I see that the Lattice Parameter for copper at at 293 K is 3.6147 x 10^-10 m which is in very close agreement with the calculated amount above. And since metals expand and contract with heat and cold, I assume the slight difference in values is due to the density figure given being determined at a temperature lower than 293 K.
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.
how is the akin of frog similar to a fish
Answer:
Have you ever touched a fish? Most fish will feel a bit rough - due to their scales. Some, like sharks, will feel like sandpaper. Even fish with small, smoother scales will feel a bit like that. Amphibians don’t have scales, and most species will be wet to some degree - they have to keep their skin moist or they’ll die. A few groups, like toads and newts, have rougher skin, which is heavier and thicker, which allows them to retain moisture better away from water.
Functionally, the big thing about amphibian skin is that it is semi-permeable. Amphibians can breathe through their skin - all amphibians can get some oxygen through their skin, but some species of salamanders get all their oxygen that way - they have no lungs or gills. The skin can also allow water in - sort of like a paper towel. The bad thing is that other chemicals can pass through the skin, too - pollutants and other chemicals tend to affect amphibians far more than they do other groups.
Amphibians also shed their skin - fish do not. People don’t tend to see frogs shedding their skin often, though, since they eat it to regain nutrients and other resources in the skin.
Finally, since amphibian skin offers no defense against predators in the way that scales do, and limited barrier against disease the way non-amphibian skin does (shedding helps), the skin of many amphibians contain toxins, and some of them have anti-fungal properties (typically due to symbiotic bacteria). Many species have evolved chemical defenses in the skin, while others have glands that produce toxins that can be secreted outside of the skin.
The skin can withstand dessication more than the fish.
They have moist skin used as respiratory surface during deep sleep / hibernation.
They have moist skin due to secretion of mucus by glands under the skin.
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