(A) Calculate the wavelength (in nm) of light with energy 1.89 × 10–20 J per photon, (b) For light of wavelength 410 nm, calculate the number of photons per joule, (c) Determine the binding energy (in eV) of a metal if the kinetic energy possessed by an ejected electron [using one of the photons in part (b)] is 2.93 × 10–19 J.

Answer:

C. 12 × 16

Explanation:

Let mH be the mass of atoms of hydrogen and mO be the mass of atoms of oxygen.  The atoms of oxygen have 16 times the mass of atoms of hydrogen. That is,

mO = 16 mH   [1]

Let mX be the mass of the atoms of X. Atoms of element X have 12 times the mass of atoms of oxygen. That is,

mX = 12 mO   [2]

If we substitute [1] in [2], we get

mX = 12 × 16 mH

If mH is 1, we get,

mX = 12 × 16 × 1

mX = 12 × 16

Answer:

2 K(s) + Cl₂(g) ⟶ 2 KCl(s)

2 Cu(s) + O₂(g) ⟶ 2 CuO(s)

Explanation:

Both reactions are synthesis reactions (two substances combine to form another).

Reaction: K(s) + Cl₂(g) ⟶

The product is the binary salt KCl. The balanced chemical equation is:

2 K(s) + Cl₂(g) ⟶ 2 KCl(s)

Reaction: Cu(s) + O₂(g) ⟶

The most likely product is the metal oxide CuO. The balanced chemical equation is:

2 Cu(s) + O₂(g) ⟶ 2 CuO(s)

Answer:

Part A

Ag+ is the Lewis acid and NH3 is the Lewis base.

Part B

AlBr3 is the Lewis acid and NH3 is the Lewis base.

Part C

AlCl3 is the Lewis acid and Cl− is the Lewis base.

Explanation:

A Lewis acid is any specie that accepts a lone pair of electrons. Ag^+, AlBr3 and AlCl3 all accepted lone pairs of electrons according to the three chemical reaction equations shown. Hence, they are Lewis acids.

A Lewis base donates a lone pair of electrons. They include neutral molecules having lone pair of electrons such as NH3 or negative ions such as Cl- .

Hydrogen sulfide ions, dihydrogen phosphate, and water are amphoteric. Therefore, option (a), (c), and (d) are correct.

Amphoteric can be stated as any compound that can be mixed with other compounds both as a base and an acid. Water is amphoteric as it can be transformed into a compound that can be mixed as an alkali or an acid.  

Amphoterism is explaining the reactivity of a compound that indicates alkaline nature when mixed with an acid and describes acidic characteristics in an alkaline environment.

When acid reacts with water, it forms H₃O⁺ ion adding an H⁺ ion from the acid. When water is combined with a base, it donates a hydrogen H⁺ ion to the base and releases a hydroxide ion.

Besides water, there are many oxides and hydroxides are utilized in amphoterism. The substances that have both characteristics acids are proton donors and bases are proton acceptors are identified as amphoteric substances.

Therefore, HS⁻, H₂O, and H₂PO₄⁻ are amphoteric in nature.

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Answer:

ZnCl2=ionic

MgS=ionic

CH4=molecular

Explanation:

ZnCl₂=ionic, MgS=ionic and CH₄=molecular compounds.

Thus, Ions with opposing charges that are kept together by electrostatic forces make up ionic compounds. Typically, a metal and a nonmetal combine to make them.

Atoms share electrons through covalent bonds to form molecular compounds.

When atoms of various elements share electrons through covalent bonds, molecules are created, also known as covalent compounds. These compounds consist of molecules made up of joined atoms, and the shared electrons strengthen the bonds between the atoms.

Thus, ZnCl₂=ionic, MgS=ionic and CH₄=molecular compounds.

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Answer: trial b

Explanation:

Answer: The correct answer is Protein B.

Explanation:

Gel-filtration chromatography is a separation technique that is based on the size of the molecules in a compound. It is also known as size-exclusion chromatography in which the eluent (carrier) used is an aqueous solution.

The matrix that is used is a porous material. When the sample is inserted in the column, the smaller particles interact strongly with the matrix than the large ones. Thus, as the eluent is passed through the matrix, larger molecules come out first, and the smallest molecule comes out last.

Given sizes of the proteins:

Protein A: 1200 kDa

Protein B: 2000 kDa

Protein C: 800 kDa

As protein B has the largest size of all the given proteins, it will emerge out first from the column.

Hence, the correct answer is Protein B.

Answer:

The mechanical properties of urea formaldehyde resins may be improved by incorporating therein polyvinyl alcohol. The polyvinyl alcohol may be incorporated during pre-mixing, mid mixing, and/or post mixing of the resin components. Resins prepared using polyvinyl alcohol are particularly desirable in articles requiring improved mechanical strength and water resistance, as compared to similar resins prepared without the polyvinyl alcohol such as shingles.

Explanation:

Iron atom is been oxidised as it losses 2 electron to form 2 + ion.

Answer:

The tasks which form the preliminaries to a descriptive investigation are: Making careful objective observations. Asking the relevant scientific questions.

Answer:

Carbon is dull, have a low density, and are poor conductors of heat.

Explanation:

Carbon is a non-metal, therefore bearing properties of a non-metal element.

Answer:

Benzene <  Cyclohexane < CH4

Explanation:

The location of a peak in an NMR spectrum is determined by chemical shift. In 1H NMR, a proton that is strongly shielded, It implies a proton that has a high electron density, is exposed to a low magnetic field, which causes the chemical shift to diminish, resulting in a signal towards the right direction of the spectrum.

However, a de-shielded proton with its electron density reduced is exposed to a high magnetic field, which causes and resulted in a chemical shift and causes it to shift to the left of the spectrum.

Electronegativity is one of the factors that influence the electron density because it decreases the proton's electron density attached to it as well as the ones attached to nearby atoms due to the inductive effect. The impact of an electronegative atom diminishes fast as the distance between them grows.

We can utilize the impact of electronegativity to calculate how much chemical shift will take place in each molecule in this question.

The chemical shift for benzene is = 7.26 ppm

Chemical shift for cyclohexane is = 1.44 ppm

Chemical shift for methane = 0.23 ppm

Thus, in decreasing order, the chemical shift with the lowest shift from left to right is:

Benzene <  Cyclohexane < CH4

Explanation:

d=ut+5

d-5=ut

d-5/t=u

!!!!!!!

Answer:

Explanation:

Answer:

SO < CO2 < C3H8

Explanation:

Entropy refers to the degree of disorderliness of a system. The standard molar entropy of a substance refers to the entropy of 1 mole of the substance vunder standard conditions.

The molar entropy depends on the number of microstates in the system which in turn depends on the number of atoms in the molecule.

C3H8 has 11 atoms and hence the highest number of microstates followed by CO2 having three atoms and least of all SO having only two atoms.

Answer:

11 protons 10 neutrons 11 electron

13 protons 14 neutrons 13 electrons

Explanation:

Isotopes are atoms of the same element having same atomic number but different mass numbers.

Answer:

pH = 8.87

Explanation:

Hydroiodic acid, HI, is a strong acid that reacts with ammonia, NH3, to produce ammonium ion, NH⁴⁺. That means the moles of HI added = moles of NH3 consumed and moles of NH4⁺ produced.

Initial moles NH₄⁺:

0.225L * (0.298mol/L) = 0.06705 moles

Initial moles NH3:

0.225L * (0.478mol/L) = 0.10755 moles

After the reaction the moles are:

0.10755moles NH3 - 0.0560moles = 0.05155 moles NH3

0.06705moles NH4+ + 0.0560moles = 0.12305 moles NH4+

Using H-H equation for weak bases:

pOH = pKb + log ([NH4+] / [NH3])

pKb for ammonia is 4.75, [NH4+] could be the moles of NH4+ = 0.12305mol,

[NH3] = 0.05155moles

Replacing:

pOH = 4.75 + log (0.12305mol / 0.05155moles)

pOH = 5.13

pH = 14-pOH

Answer:

a) will react with water: K

b) will react with steam or acid, but not water: Cr & Sn

d) will not react with water, steam, or acid: Cu

Explanation:

K reacts violently with water.

Cr will react with steam to form an oxide + H gas and will react with most acids

Sn will react with steam to form SnO₂ + H gas and, though it does not react as rapidly as other metals in acid, it dissolves easily in concentrated acids

Cu is an extremely nonreactive metal, which is what makes it so suitable for wiring

Answer:

Molarity: 0.092M

Molality: 0.090m

Explanation:

Molarity, M, is defined as the moles of solute (In this case, C14H12 -Molar mass: 180.25g/mol-) in 1L of solution.

The molality, m, are moles of solute per kg of solvent.

Molarity:

Moles solute:

7.9g * (1mol/180.25g) = 0.04383 moles

Liters solution:

475mL = 0.475L

Molarity: 0.04383 moles / 0.475L = 0.092M

Molality:

kg solvent:

475mL * (1.03g/mL) = 489.25g = 0.48925kg

Molality:

0.04383 moles / 0.48925kg = 0.090m

Answer: here you go

Explanation:

Physical properties of the substances in a mixture are different, so this allows the substances to be separated. Think about the example of a mixture of salt water.

Answer:

Mixtures can be classified on the basis of particle size into three different types: solutions, suspensions, and colloids. The components of a mixture retain their own physical properties. These properties can be used to separate the components by filtering, boiling, or other physical processes.

Explanation:

Answer:

a. True

Explanation:

From the basic concepts of acids and bases, we know that when a base accepts a hydrogen ion (H⁺), it forms a conjugate acid which can accept again the H⁺ ion:

B⁻ + H₂O ⇆ BH + OH⁻

The stronger the base, the weaker the conjugate base. Thus, as more strength has a base, lesser strength will have the conjugate base (it will not be able to accept again the H⁺ ion). For example, when water (H₂O) loses its H⁺ , it forms the conjugate base OH⁻. So, OH⁻ is the stronger base that can exist in an aqueous solution.

H₂O ⇆ H⁺ + OH⁻

In fact, strong bases are hydroxides, such as NaOH or KOH.

Answer: The standard way to report this result is [tex]32.9\pm 0.3 mL[/tex]

Explanation:

The standard method of representing a result is:

[tex]\text{Calculated value }\pm \text{ Standard deviation}[/tex]

The reporting of a result is done in correct significant figures.

We are given:

Calculated value = 32.9 mL

Standard deviation = 0.3 mL

Rule of significant figures applied when numbers are added or subtracted:

The number having less number of significant figures after the decimal point will determine the number of significant figures in the final answer.

Number of significant figures after the decimal point = 1

Hence, the standard way to report this result is [tex]32.9\pm 0.3 mL[/tex]

Answer:

yes the experimental result is the expected result .

Explanation:

When Titrating acetate buffer with acid the PH will decrease gradually from a more neutral PH to a more acidic level and this is because buffer solutions are prepared with weak acids and its conjugate base.

The results gotten from the continuous addition of base NaOH to the acetate buffer is the expected result because the base is been absorbed by the buffer solution and it is converted to a conjugate base of the buffer solution which will gradually increase the PH level of the solution as more conjugate base is formed due to the addition of more NaOH.  

Answer:

D.) ±0.01 cm?​

Explanation:

Since 32.23 cm has two decimal places, the uncertainty is taken as one-half the last decimal pace.

The last decimal place is 0.03. Half of this is 0.03 cm/2 = 0.015 cm.

Since we cannot go below two decimal places, we ignore the 5 in 0.015 cm.

So, we have our uncertainty as 0.01 cm.

So, the best expression of the uncertainty in the measurement 32.23 cm is ± 0.01 cm.

So, the answer is D. which is ± 0.01 cm.

Answer:

0.10 M Ca(CH3COO)2- Less soluble than in pure water.

0.10 M K2SO3- Less soluble than in pure water.

0.10 M NaNO3 - More soluble than in pure water.

0.10 M KCH3COO- Similar solubility as in pure water.

Explanation:

We have to cast our minds back to the idea of common ions effect. If any ion is already present in solution, the presence of that ion in solution prevents any solute containing a common ion with the solution from dissolving in that solution. In order words, the presence of a common ion makes a solute less soluble in a solvent than it is in pure water.

For instance, 0.10 M Ca(CH3COO)2 and K2SO3 both contain Ca^2+ and SO3^2- ions respectively which are also contained in the solute calcium sulfite.

The presence of these common ions in solution makes calcium sulfite less soluble in these solutions than it is in pure water because the equilibrium position for the dissolution of the solute lies towards the left hand side.

However, calcium sulfite is more soluble in 0.10 M NaNO3 than in pure water due to displacement reaction between the ions in solution.

The solubility of calcium sulfite and 0.10 M KCH3COO in pure water is quite comparable.

Answer:

On heating, the van der Waals dispersion forces existing then will easily break as it has a low boiling point and sublimates into gas. On heating iodine in the test tube, iodine evolves as violet fuming gas.

Explanation:

Answer:

Số gam muối ăn cần là 76:42,7%=177,986 g

Explanation: