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1 year ago

For a hydrogen atom, which electronic transition would result in the emission of a photon with the highest energy?

Chemistry

1 answer:

BartSMP [9]1 year ago

6 0

Answer: A

Explanation:

Considering the order of filling electrons into orbitals, movement from a higher to a lower energy level results in the emission of a photon with energy equal to the energy difference between the two energy levels. However, the energies of different orbitals are close together for high values of n (principal quantum number). Their relative energies may change significantly when they form ions. This implies that energy levels are better separated and have high differences in energy for low values of n. Hence the answer. This means that photons transiting between these Lowe n levels will posses higher photon energy due to larger energy difference between levels.

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Magnesium burns in air with a dazzling brilliance to produce magnesium oxide: 2Mg (s) + O2 (g) →→ 2MgO (s) When 4.50 g of magnes

Klio2033 [76]

Answer:

7.46 g

Explanation:

From the balanced equation, 2 moles of Mg is required for 2 moles of MgO.

The mole ratio is 1:1

mole = mass/molar mass

mole of 4.50 g Mg = 4.50/24.3 = 0.185 mole

0.185 mole Mg will tiled 0.185 MgO

Hence, theoretical yield of MgO in g

mass = mole x molar mass

0.185 x 40.3 = 7.46 g

6 0

2 years ago

Read 2 more answers

A compound of barium and oxygen was dissolved in hydrochloric acid to give a solution of barium ion, which was then precipitated

n200080 [17]

Answer:

The empiricial formula of the compound is BaO2

Explanation:

Step 1: Data given

Barium and oxygen dissolved in hydrochloric acid gives a solution of barium ion. This was precipitated with an excess of potassium chromate and gives barium chromate.

The original compound weighs 1.345g and gives 2.012g of BaCrO4

Step 2: Calculate moles of BaCrO4

moles of BaCrO4 = mass of BaCrO4 / molar mass of BaCrO4

moles of BaCrO4 = 2.012g / 253.37 g/mol = 0.0079 moles

Step 3: Calculate moles of Ba

Mole ratio for Ba and BaCrO4 is 1:1 so this means for 0.0079 moles of BaCrO4, there are 0.0079 moles of Ba-ion

Step 4: Calculate mass of Ba-ion

Mass of Ba = Moles of Ba / Molar mass of Ba

Mass of Ba = 0.0079 moles * 137.327g/mole = 1.085 g Ba

Step 5: Mass of oxygen

Since the original compound has barium and oxygen, the mass of oxygen is the difference between the original mass and the mass of the Ba-ion

1.345 g - (1.085 g Ba) = 0.260 g O

Step 6: Calculate moles of Oxygen

moles oxygen = mass of oxygen / Molar mass of oxygen

moles oxygen = 0.260g / 16g/mole = 0.01625 moles O

We divide the number of moles by the smallest number of moles which is 0.0079

Ba → 0.0079/0.0079 = 1

O → 0.01625 / 0.0079 ≈ 2

(1.091 g Ba) / (137.3277 g Ba/mol) = 0.00794450 mol Ba

(0.254 g O) / (15.99943 g O/mol) = 0.0158756 mol O

This gives us the empirical formula of BaO2 for this compound

7 0

1 year ago

What is the minimum pressure in kPa that must be applied at 25 °C to obtain pure water by reverse osmosis from water that is 0.1

Yuri [45]

Answer:

The minimum pressure should be 901.79 kPa

Explanation:

Step 1: Data given

Temperature = 25°C

Molarity of sodium chloride = 0.163 M

Molarity of magnesium sulfate = 0.019 M

Step 2: Calculate osmotic pressure

The formula for the osmotic pressure =

Π=MRT.

⇒ with M = the total molarity of all of the particles in the solution.

⇒ R = gas constant = 0.08206 L*atm/K*mol

⇒ T = the temperature = 25 °C = 298 K

NaCl→ Na+ + Cl-

MgSO4 → Mg^2+ + SO4^2-

M = 2(0.163) + 2(0.019 M)

M = 0.364 M

Π = (0.364 M)(0.08206 atm-L/mol-K)(25 + 273 K)

Π = 8.90 atm

(8.90 atm)(101.325 kPa/atm) = 901.79 kPa

The minimum pressure should be 901.79 kPa

6 0

2 years ago

When double-stranded DNA is heated at neutral pH, which change does not occur?

Sindrei [870]

Answer:

B) The covalent N-glycosidic bond between the base and the pentose breaks

Explanation:

When forces that bind 2 DNA strands are broken, these strands finally split. This process is called denaturalization

The main forces that remain both DNA strands together are the hydrogen bonds (physical forces), between pair of bases (Adenine with Thymine, and Guanine with Cytosine)

Denaturalization may occur by different factor: Ph alteration, salt addition, temperature (heating), etc

When heating a DNA solution, denaturalization process may be followed using UV absorption (normally, at wavelength of 260 nm): when DNA (double strand) has its regular structure, UV light absorption is low, as the nitrogen bases are stacked like a pile of coins, for which structure absorbs less light

When DNA structure is denaturalized, these nitrogen bases are exposed, and UV absorption increases

Also, DNA denaturalization may be followed by viscosity: for a double strand DNA solution, viscosity is high due to double chain stiffness but when strands are denaturalized, simple strands solution are less viscous (so viscosity decreases over time, when heating the solution)

Lastly, when solution is heated, only physical forces are broken (hydrogen bonds) and not chemical bonds (such as covalent bonds), for which extreme conditions are needed

7 0

1 year ago

N2(g) + 3h2(g) ⇌ 2nh3(g) the equilibrium constant kc at 375°c is 1.2. starting with [h2]0 = 0.76 m, [n2]0 = 0.60 m and [nh3]0 =

nekit [7.7K]

N2(g) + 3 H2(g) = 2NH3(g)

Qc = (NH3^2) / { (N2)(H)^3)}

Qc= 0.48^2 /{ ( 0.60) (0.760^3) }= 0.875

Qc < Kc therefore the equilibrium will shift to the right. This implies that Nh3 concentration will increase

8 0

2 years ago