explain in brief how some bacteria cause tooth cavities
Answer:
because some bacteria change the ph of the teeth and leads to tooth cavitiew
Which statement is true with respect to standard reduction potentials?
SRP values that are greater than zero always represent a reduction reaction.
SRP values that are less than zero always represent a reduction reaction.
Half-reactions with SRP values greater than zero are spontaneous.
Half-reactions with SRP values greater than zero are nonspontaneous.
Answer:
C). Half-reactions with SRP values greater than zero are spontaneous.
Explanation:
SRPs or Standard Reduction Potentials are characterized as the ability of a probable distinction among the anode and cathode of a usual/standard cell. It aims to examine the capacity of chemicals to reduce themselves.
The third statement asserts a true claim regarding the SRPs(Standard Reduction Potentials) that the 'half-reactions which take place with the SRP possesses the values higher than zero and they are unconstrained.' The other statements are incorrect as they either show the estimation of SRPs more than 0 or display them as being restricted. Thus, option C is the correct answer.
For a gas sample containing equimolar amounts of carbon monoxideand heliumat 300 K, heliumhas _____________average speed and _____________ average kinetic energy compared tocarbon monoxidegas.a.a lower; the same b. the same; the same c. a higher; the same d. a higher; higher
Answer:
Option C (a higher; the same) is the appropriate response.
Explanation:
Given:
Temperature,
T = 300 K (both [tex]N_2[/tex] and [tex]H_2[/tex])
As we know,
Average speed of a molecule,
⇒ [tex]\bar v=\sqrt{\frac{8RT}{\pi M} }[/tex]
Thus, the average speed of [tex]N_2[/tex] will be lower as its molar mass is greater than [tex]H_2[/tex].
Now,
⇒ [tex]Average \ kinetic \ energy = \frac{3}{2} \ KT[/tex] (not depend on molar mass)
Hence, it will be the same.
The other three alternatives aren't connected to the scenario given. So the above is the correct answer.
An endothermic reaction will start when the required
energy is received from the environment or solution.
AH
activation
thermal
kinetic
Answer:
A: ΔH
Explanation:
Endothermic reactions are this that occur as a result of absorption of heat energy from the surroundings by the reactants to form new products.
Thus, we can say it is one with an increase in enthalpy (ΔH) of the system.
Thus, option A is correct.
it takes 513 kj to remove a mole of electrons from the atoms at the surface of a piece of metal. how much energy does it take to remove a single electron from n atom at the surface of the metal
Answer:
The right solution is "[tex]8.5\times 10^{-19} \ joule[/tex]".
Explanation:
As we know,
1 mole electron = [tex]6.023\times 10^{23} \ no. \ of \ electrons[/tex]
Total energy = [tex]513 \ KJ[/tex]
= [tex]513\times 1000 \ joule[/tex]
For single electron,
The amount of energy will be:
= [tex]\frac{513\times 1000}{(6.023\times 10^{23})}[/tex]
= [tex]8.5\times 10^{-19} \ joule[/tex]
Poly(ethylene terephthalate) (PET), which has glass transition (Tg) and crystalline melting (Tm) temperature of 69 and 267 °C, respectively, can exist in a number of different states depending upon temperature and thermal history. Thus, it is possible to prepare materials that are semicrystalline with amorphous regions that are either glassy or rubbery and amorphous materials that are glassy, rubbery or melts. Consider a sample of PET cooled rapidly from 300 °C (state A) to room temperature. The resulting material is rigid and perfectly transparent (state B). The sample is then heated to 100 °C and maintained at this temperature, during which time is gradually becomes translucent (state C). It is then cooled to room temperature, where it is again observed to be translucent (state D).
Answer:
Following are the solution to the given points:
Explanation:
For point A:
The sample cooking (PET) is between 300°C and room temperature.Now in nature, the substance is exceedingly stiff.Samples of PET up to 100°C were heated and stayed on equal footing.Now it has cooled off the same sample below 100° C and we may see how it is again TRASNEPARENT in nature.For point B:
In point 3, the mixture was added to 100°C, which implies that the granular material flows and deforms, enabling it to become elongated. This is termed solid-state crystalline such that grains are flexible, but this material contaminates numerous little crystalline that has spheres when we cool down in point 4 polymers. It forms therefore an unstructured solid, which then in point 4 is higher in particles and less pliable in orderly atoms.
For point C:
In point 2, the specimen gets forced at room temperature to organize a huge molecule in an ordinary and crystal fashion and therefore is transparent due to highly crystalline atoms in point 2 of the PET sample.
In point 4, however, we notice how amorphous, firm but not crystalline develops. It's why light tends to disperse over many cereal limits, since many microscopic crystallines, therefore dispersion, PET in point 4 is translucent.
Calculate percent yield when you start with 0.78 grams of camphor and end with 0.23 grams of iso/borneol. The molecular weight of camphor is 152.23 g/mol, and the molecular weight of iso/borneol is 154.25 g/mol.
Answer:
29.1%
Explanation:
First we convert 0.78 g of camphor to moles, using its molar mass:
0.78 g ÷ 152.23 g/mol = 0.00512 mol camphorThen we convert 0.23 g of isoborneol to moles, using its molar mass:
0.23 g ÷ 154.25 g/mol = 0.00149 mol isoborneolFinally we calculate the percent yield:
0.00149 mol / 0.00512 mol * 100% = 29.1%
the carbon tetrachloride molecule CCI 4 is
Answer:
is a nonpolar molecule with polar bonds
Identify the highest energy molecular process that occurs when a molecule absorbs a microwave photon.
The question is incomplete, the complete question is;
Identify the highest energy molecular process that occurs when a molecule absorbs a microwave photon
a) electronic excitation
b) bond breakage
c) molecular vibration
d) molecular rotation
Answer:
molecular rotation
Explanation:
Microwaves are part of the electromagnetic spectrum. They are lower energy, lower frequency radiation.
When molecules absorb infrared radiation, they transition between the rotational states of the molecule.
Hence, the highest energy molecular process that occurs when a molecule absorbs a microwave photon is molecular rotation.
An electrolysis reaction is
A)
exothermic.
B)
hydrophobic.
C)
spontaneous.
D)
non-spontaneous.
Answer:
the electrolysis reaction is a non- spontaneous reaction
Explanation:
Since electrons flow from it, the anode in an electrolytic cell is positive, while the cathode is negative when electrons flow into it. The device functions like a galvanic cell in that direction. In an electrolytic cell, an external voltage is applied and that is what causes a non spontaneous reaction
When perchloric acid (HClO4) reacts with tetraphosphorus decaoxide, phosphoric acid and dichlorine heptaoxide are produced.
a. Trei
b. False
Answer:
я не знаю ответа :(
Explanation:
What is the major product in this reaction
Answer:
I think option A is right answer
A sample of oxygen gas has a volume of 89.6 L at STP. How many moles of oxygen gas are present ?
Answer:
89,6/22,4 =4(mol)
Explanation:
There are approximately 1.089 moles of oxygen gas present in the sample at STP.
At STP (Standard Temperature and Pressure), the conditions are defined as follows:
Temperature (T) = 0 degrees Celsius = 273.15 Kelvin
Pressure (P) = 1 atmosphere (atm) = 101.325 kPa = 1013.25 hPa
Now, to find the number of moles of oxygen gas (O2) present in the sample, we can use the ideal gas law:
PV = nRT
Where:
P = pressure (in atm)
V = volume (in liters)
n = number of moles
R = ideal gas constant = 0.0821 L.atm/(mol.K)
T = temperature (in Kelvin)
Given:
V = 89.6 L (volume at STP)
T = 273.15 K (STP temperature)
Let's plug in the values and solve for n (number of moles):
n = PV / RT
n = (1 atm) × (89.6 L) / (0.0821 L.atm/(mol.K) × 273.15 K)
n = 1.089 moles
So, there are approximately 1.089 moles of oxygen gas present in the sample at STP.
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A molecule of acetone and a molecule of propyl aldehyde are both made from 3 carbon atoms, 6 hydrogen atoms, and 1 oxygen atom. The molecules differ in their arrangement of atoms. How do formulas for the two compounds compare? Both compounds have the same molecular formula, but have unique structural formulas. Both compounds have unique molecular formulas and structural formulas. Both compounds have the same structural formula, but have unique molecular formulas.
Explanation:
The structures of both acetone and propanal are shown below:
In the formula of propanal there is -CHO functional group at the end.
In acetone -CO- group is present in the middle that is on the second carbon.
The molecular formula is C3H6O.
Both have same molecular formula but different structural formulas.
When 4.41g of phosphoric acid (H3PO4) react with 9.25g of barium hydroxide, water and insoluble barium phosphate form. [T/I-7] a. Write and balance the chemical equation.
Answer:
2 H₃PO₄(aq) + 3 Ba(OH)₂(aq) ⇒ Ba₃(PO₄)₂(s) + 6 H₂O(l)
Explanation:
Let's consider the unbalanced equation that occurs when phosphoric acid reacts with barium hydroxide to form water and barium phosphate. This is a neutralization reaction.
H₃PO₄(aq) + Ba(OH)₂(aq) ⇒ Ba₃(PO₄)₂(s) + H₂O(l)
We will balance it using the trial and error method.
First, we will balance Ba atoms by multiplying Ba(OH)₂ by 3 and P atoms by multiplying H₃PO₄ by 2.
2 H₃PO₄(aq) + 3 Ba(OH)₂(aq) ⇒ Ba₃(PO₄)₂(s) + H₂O(l)
Finally, we will get the balanced equation by multiplying H₂O by 6.
2 H₃PO₄(aq) + 3 Ba(OH)₂(aq) ⇒ Ba₃(PO₄)₂(s) + 6 H₂O(l)
When butane reacts with Br2 in the presence of Cl2, both brominated and chlorinated products are obtained. Under such conditions, the usual selectivity of bromination is not observed. In other words, the ratio of 2-bromobutane to 1-bromobutane is very similar to the ratio of 2-chlorobutane to 1-chlorobutane. Can you offer and explanation as to why we do not observe the normal selectivity expected for bromination
Answer:
Bromine radical formation is carried out in the presence of Br₂ and Cl₂ causing the normal selectivity not to be observed ( this causes the difference in activation energy to be reduced )
Explanation:
Why the normal selectivity expected for bromination is not observed
On the basis of selectivity and applying the Arrhenius equation the greater the difference between the activation energies the more the selectivity.
as seen in the formation of primary and secondary radicals in the Bromine radical formation. this difference is caused mainly by the propagation step ( exothermic ) . But the main reason why the the usual selectivity of bromination is not observed is because it Bromine radical formation is carried out in the presence of Br₂ and Cl₂ ( this causes the difference in activation energy to be reduced )
0.50 g of hydrogen chloride (HCl) is dissolved in water to make 4.0 L of solution. What is the pH of the resulting hydrochloric acid solution
Explanation:
Given the mass of HCl is ---- 0.50 g
The volume of solution is --- 4.0 L
To determine the pH of the resulting solution, follow the below-shown procedure:
1. Calculate the number of moles of HCl given by using the formula:
[tex]number of moles of a substance=\frac{given mass of the substance}{its molecular mass}[/tex]
2. Calculate the molarity of HCl.
3. Calculate pH of the solution using the formula:
[tex]pH=-log[H^+][/tex]
Since HCl is a strong acid, it undergoes complete ionization when dissolved in water.
[tex]HCl(aq)->H^+(aq)+Cl^-(aq)[/tex]
Thus, [tex][HCl]=[H^+][/tex]
Calculation:
1. Number of moles of HCl given:
[tex]number of moles of a substance=\frac{given mass of the substance}{its molecular mass}\\=0.50g/36.5g/mol\\=0.0137mol[/tex]
2. Concentration of HCl:
[tex]Molarity of HCl=\frac{number of moles of HCl}{its molar mass}\\=\frac{0.0137 mol}{4.0 L} \\= 0.003425 M[/tex]
3. pH of the solution:
[tex]pH=-log[H^+]\\=-log(0.003425)\\=2.47[/tex]
Hence, pH of the given solution is 2.47.
Classify the following as either solutions or colloids. If a colloid, name the type of colloid and identify both the dispersed and the dispersing phases.
a. glucose in water
b. smoke in air
c. carbon dioxide in air
d. milk
Answer:
a. glucose in water( solution)
b. smoke in air (colloids)
c. carbon dioxide in air (solution)
d. milk( colloids)
Explanation:
A solution is said to be formed when a solute dissolves in a solvent to form a homogeneous mixture. The solute particles are less than 10^-9m in size. Familiar solutions are those where the solute are dissolved in a liquid solvent. When the liquid water, the solution is known as an aqueous solution. A typical example is (glucose in water). In some other cases, the apparent solution of a solute in a solvent is accompanied by a chemical reaction and this is often known as a chemical reaction. A typical example is (carbon dioxide in air).
Colloids are also known as false solutions. Here, the individual solute particles are larger than the particles of the true solution, but not large enough to be seen by the naked eye. When a light beam is placed beside a beaker containing a colloid, the light rays of the beam can be clearly seen. This shows that it exhibits the Tyndall effect while a solution dosent exhibit such.
In a colloid, the liquid solvent is more appropriately know as the DISPERSION medium while the solid solute particles constitute the DISPERSED substance. This can either be solid, liquid or gas.
For example:
--> smoke in air : Dispersion medium is gas while the dispersed substance is solid.
--> milk: Dispersion medium is liquid while the dispersed substance is liquid.
A gas mixture, with a total pressure of 300. torr, consists of equal masses of Ne (atomic weight 20.) and Ar (atomic weight 40.). What is the partial pressure of Ar, in torr
Answer:
The partial pressure will be "100 torr".
Explanation:
Given:
[tex]P_{Ar} = 300 \ torr[/tex]
By assuming Ar and Ne having 50 gm each, we get
mol of Ne = [tex]\frac{50}{20}[/tex]
= [tex]2.5 \ mol[/tex]
mol of Ar = [tex]\frac{50}{40}[/tex]
= [tex]1.25 \ mol[/tex]
now,
[tex]n_T= mol.A_r+mol.N_e[/tex]
[tex]=1.25+2.5[/tex]
[tex]=3.75[/tex]
then,
[tex]X_{Ar}=\frac{n_{Ar}}{n_T}[/tex]
[tex]=\frac{1.25}{3.75}[/tex]
[tex]=0.33[/tex]
hence,
The partial pressure of Ar will be:
⇒ [tex]P_{Ar} = P_T\times X_{AT}[/tex]
By substituting the values, we get
[tex]=300\times 0.33[/tex]
[tex]=100 \ torr[/tex]
The partial pressure of Ar in the mixture is 99.9 torr
Let the mass of both gas be 10 g
Next, we shall determine mole of each gas.
For Ne:Mass = 10 g
Molar mass of Ne = 20 g/mol
Mole of Ne =?Mole = mass / molar mass
Mole of Ne = 10 / 20
Mole of Ne = 0.5 mole For Ar:Mass = 10 g
Molar mass of Ar = 40 g/mol
Mole of Ar =?Mole = mass / molar mass
Mole of Ar = 10 / 40
Mole of Ar = 0.25 moleNext, we shall determine the mole fraction of Ar
Mole of Ne = 0.5 mole
Mole of Ar = 0.25 mole
Total mole = 0.5 + 0.25 = 0.75 mole
Mole fraction of Ar =?[tex]mole \: fraction \: = \frac{mole}{total \: mole} \\ \\ mole \: fraction \: of \:Ar = \frac{0.25}{0.75} \\ \\ mole \: fraction \: of \:Ar = 0.333 \\ \\ [/tex]
Finally, we shall determine the partial pressure of Ar
Mole fraction of Ar = 0.333
Total pressure = 300 torr
Partial pressure of Ar =?Partial pressure = mole fraction × total pressure
Partial pressure of Ar = 0.333 × 300
Partial pressure of Ar = 99.9 torrLearn more on partial pressure: https://brainly.com/question/15577259
Write the symbol for every chemical element that has atomic number greater than 70 and atomic mass less than 185.2
Answer:
HF...Ta... W....Lu...
Tema: Métodos de Separação de Misturas – Homogêneas e Heterogêneas;
1. Capa (0,5 ponto)
2. Índice ou Sumário (0,5 ponto)
3. Texto do trabalho
a) Introdução (1,0 ponto)
b) Objetivos (0,5 ponto)
c) Método (0,5 ponto)
d) Desenvolvimento: Fundamentação Teórica (5,0 pontos)
e) Conclusão (1,0 ponto)
4. Bibliografia (1,0 ponto)
Answer:
fjskeowkcnekvo Dee five votes come vote for dog even r
dentify the correct formula for the following ionic compounds. - sodium chloride - magnesium chloride - calcium oxide - lithium phosphide - aluminum sulfide - calcium nitride A. SCl B. LiP 3 C. AlS D. Li 3P E. CaN F. CaO G. Ca 3N 2 H. MgCl 2 I. NaCl J. CaO 2 K. CaN 2 L. LiP M. MnCl 2 N. Al 2S 3 O. AlS 3
Explanation:
The chemical formula of an ionic compound can be written by using the symbols of the respective cations and anions.
The overall charge on the molecule should be zero.
Hence, the total charge of cations=total charge of anions.
The symbols of the given molecules are shown below:
sodium chloride ---- NaCl
magnesium chloride ---[tex]MgCl_2[/tex]
calcium oxide ---- CaO
lithium phosphide----[tex]Li_3P[/tex]
aluminum sulfide ----- [tex]Al_2S_3[/tex]
calcium nitride---- [tex]Ca_3N_2[/tex]
cual es la masa atomica del hidrogeno
El hidrógeno es el elemento químico de número atómico 1, representado por el símbolo H. Con una masa atómica de 1.00784 u es el más ligero de la tabla periódica de los elementos. Por lo general, se presenta en su forma molecular, formando el gas diatómico H₂ en condiciones normales.
Bond length is the distance between the centers of two bonded atoms. On the potential energy curve, the bond length is the internuclear distance between the two atoms when the potential energy of the system reaches its lowest value.
a. True
b. False
Answer:
True
Explanation:
When two atoms are at infinite distance from each other, the both atoms posses high energy.
However, as they begin to approach each other, the distance between them gradually decreases and so does their energy.
A point is eventually reached when the potential energy curve reaches its minimum value. The internuclear distance between the two atoms at this point is called the bond length of the system.
DATA SHEET p 45. TRIAL 1 TRIAL 2 1. Mass of the ground pretzel 1.00 gram 1.03 g 2. Initial volume of the AgNO3 solution 0.00 mL 9.10 mL 3. Final volume of the AgNO3 solution 9.10 mL 17.25 mL 4. Volume of AgNO3 solution used 9.10 mL 8.15 mL Line 3 – Line 2 5. Volume of AgNO3 solution in liters _____ L _____ L 6. Molarity of AgNO3 solution 0.01 M 0.01 M (given) 7. Number of moles of AgNO3 ______ mol _____ mol (Line 5 × Line 6) 8. Number of mol of NaCl present in pretzel ______ mol _____ mol (Line 7) number of mol NaCl = number of mol AgNO3 9. Mass of NaCl present in the titrated sample ______ gram _____ gram (Line 8) × 58.5 g/mol
Answer:
1. 1.00 gm
2. 50 ml
3. 38.93 ml
4. 11.07 ml
5. 0.01107 L
6. 0.010 moles / L
7. 0.0001107 moles
8. 0.0001107 moles
9. 0.00647042 grams
Explanation:
Silver nitrate can react with various compounds to form different products. The weight of products may be different from the original solution introduced due to combustion reaction, as heat energy is released during the chemical process.
Identify the oxidation half-reaction for this reaction:
Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g)
A. Fe2+ + 2e → Fe(s)
O B. H2(g) → 2H+ + 2e
O C. Fe(s) → Fe2+ + 2e
O D. 2H+ + 2e → H2(9)
Answer:
Fe(s)->Fe2+2e-
Explanation:
A.p.e.x
The oxidation half-reaction for the given reaction is Fe(s) → Fe²⁺ + 2e⁻ Hence, Option (C) is correct
What is Oxidation reaction ?Oxidation reaction is a chemical reaction which can be described as follows ;
Addition of oxygen Removal of hydrogen Loss of ElectronAddition of electronegative atomRemoval of Electropositive elementIn the given reaction ;
Fe(s) + 2HCl(aq) → FeCl₂(aq) + H₂(g)
Fe at RHS got converted to Fe²⁺ state at LHS which shows the gain of electron by Fe with in the reaction.
Therefore,
The oxidation half-reaction for the given reaction is Fe(s) → Fe²⁺ + 2e⁻ Hence, Option (C) is correct
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_________one moleculetwo moleculesone moletwo moles of H2(g) reacts with _________one moleculetwo moleculesone moletwo moles of F2(g) to form _________one moleculetwo moleculesone moletwo moles of HF(g).
Answer:
The reaction between hydrogen and fluorine.
Explanation:
The balanced chemical equation of the reaction is:
[tex]H_2(g)+F_2(g)->2HF(g)[/tex]
From the balanced chemical equation, it is clear that:
1 mole of [tex]H_2[/tex] gas reacts with one mole of [tex]F_2(g)[/tex] and forms 2 moles of HF(g).
5. A beam of photons with a minimum energy of 222 kJ/mol can eject electrons from a potassium surface. Estimate the range of wavelengths of light that can be used to cause this phenomenon. Show your calculations with units of measure (dimensional analysis) and briefly explain your reasoning.
Answer: The range of wavelengths of light that can be used to cause given phenomenon is [tex]8.953 \times 10^{21} m[/tex].
Explanation:
Given: 222 kJ/mol (1 kJ = 1000 J) = 222000 J
Formula used is as follows.
[tex]E = \frac{hc}{\lambda}[/tex]
where,
E = energy
h = Planck's constant = [tex]6.625 \times 10^{-25} Js[/tex]
c = speed of light = [tex]3 \times 10^{8} m/s[/tex]
Substitute the values into above formula as follows.
[tex]E = \frac{hc}{\lambda}\\222000 J = \frac{6.625 \times 10^{-34}Js \times 3 \times 10^{8} m/s}{\lambda}\\\lambda = 8.953 \times 10^{21} m[/tex]
Thus, we can conclude that the range of wavelengths of light that can be used to cause given phenomenon is [tex]8.953 \times 10^{21} m[/tex].
What is the correct order for the reactions that produce the following transformation. a. (1) H2/Lindlar (2) CH3CO2OH b. (1) H2/Lindlar (2) O3, Zn, HCl c. (1) H2/Pd (2) CH3CO2OH d. (1) Na, NH3 (2) CH3CO2OH
Answer:
Explanation:
Can you provide a picture? I can outline the reactions though. a) will make a Z double bond from a triple bond and then peroxyacid can do epoxidation. b) will make the Z double bond then ozonolysis to double bond will create to aldehyde compounds. c) is essentially useless unless there is a ketone or aldehyde in the compound already since H2/Pd will fully reduce the alkyne (which I am assuming is present) and so the peroxyacid can't do epoxidation and can only do baeyer villiger oxidation, and d) reduces the alkyne to an E alkene and then do epoxidation to give an epoxide (with trans steroechemistry)
Determine whether the reaction will be spontaneous at high temperatures only, at low temperatures only, at all temperatures, or no temperatures. (HINT: Use your chemical sense and your real-world knowledge to predict the signs of delta Hrxn & delta Srxn)
4Fe(s) + 3O2(g) ----> 2Fe2O3(s) [rust]
Circle one:High T, Low T, All T, No T
Answer:
The rusting of iron is spontaneous at low temperatures.
Explanation:
The given chemical reaction is:
4Fe(s) + 3O2(g) ----> 2Fe2O3(s) [rust]
The rusting of iron is a chemical reaction in which iron reacts with oxygen in presence of moisture and forms iron oxide.
This reaction takes place in a faster rate when there is low temperatures in the atmosphere.
When temperature is low, the moisture in the atmosphere is more and hence, rate of rusting is more.
