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larisa86 [58]
3 years ago
9

Fireworks that contain metallic salts such as sodium, strontium, and barium can generate bright colors. a technician investigate

s what colors are produced by the metallic salts by performing flame tests. during a flame test, a metallic salt is heated in the flame of a gas burner. each metallic salt emits a characteristic colored light in the flame. 72 explain why the electron configuration of 2-7-1-1 represents a sodium atom in an excited state. [1]
Chemistry
1 answer:
Tasya [4]3 years ago
7 0

Answer is: The electrons moved from the second energy level to the fourth.

Atomic number (Z) of sodium is 11, it means that it has 11 protons and 11 electrons, so atom of sodium is neutral.

Electron configuration of sodium atom in a ground state:

₁₁Na 1s² 2s² 2p⁶ 3s¹ or 2-8-1-0.

In a ground state of sodium atom, fourth energy level is empty.

In a excited state electron from second energy level (2s² 2p⁶) moves to fourth energy level.

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A balloon is filled with 35L of helium in the morning when the temperature is 20C. By noon the temperature has risen to 45C. Wha
neonofarm [45]

Answer: 38L

Explanation:

Initial volume of helium V1 = 35 L

Initial temperature T1 = 20°C

Convert temperature in Celsius to Kelvin

(20°C + 273 = 293K)

New volume V2 = ?

New Temperature T2 = 45°C

(45°C + 273 = 318K)

Since, volume and temperature are involved while pressure is constant, apply the formula for Charles' Law:

(V1/T1) = (V2/T2)

35L/293K = V2/318K

0.119 = V2/318K

To get V2, cross multiply

V2 = 0.119 x 318

V2 = 38L

Thus, the new volume of the balloon is 38 liters

8 0
3 years ago
Dissolving 5.28 g of an impure sample of calcium carbonate in hydrochloric acid produced 1.14 l of carbon dioxide at 20.0 °c an
kvv77 [185]

Answer:

Percentage by mass of calcium carbonate in the sample is 93.58%.

Explanation:

Assumptions:

  • calcium carbonate was dissolved completely and the amount of carbon dioxide released was proportional to the amount of calcium carbonate.
  • the sample did not contain any other compound that released or reacted with carbon dioxide.

PV = nRT

n = \frac{PV}{RT}

P = 791 mmHg = \frac{791 mmHg}{760 mmHg} x 1 atm = 1.040789 atm.

R = 8.314 \frac{J}{K*mol} = 0.082 \frac{L*atm}{K*mol}

T = 20^{0}C + 273^{0} C = 293 K

n = \frac{1.040789 atm * 1.14 L}{0.082 \frac{L * atm}{K * mol} * 293 K }

n = 0.0493839 mol.

given the equation of the reaction:

CaCO_{3}  + 2HCL =  CaCl_{2}  + CO_{2} + H_{2}O

from assumption:

amount carbon dioxide = amount of calcium carbonate

n(CaCO_{3} ) = n(CO_{2} )

reacting mass ( m )  = Molar Mass ( M ) * Amount ( n )

m(CaCO_{3} )   =   n(CaCO_{3} )  *   M(CaCO_{3} )

m = 0.04938397 mol * 100 \frac{g}{mol} =  4.93839 g

percentage by mass of   CaCO_{3} = \frac{mass of pure  }{mass of impure}*100  = \frac{4.93839g}{5.28g}*100  = 93.5802%.

8 0
3 years ago
Cuales son los cambios que siempre envuelven cambios en la compocision de la sustancia?
QveST [7]

I already answered this question in Spanish language. Now I answer in English.


Answer: the chemical changes.


Explanation:


We understand by composition of a substance to the proportion (ratio or percentage) of each element (type of atoms) that makes up the same, as well as the way in which these elements are linked (chemical bonds).


A chemical change is a process, also called a chemical reaction, in which one or more substances are converted into different substances.


The resulting substances are different because their composition is different, since some chemical bonds have been broken and others have been formed, giving rise to a new structure. The chemical formula of each compound product of the chemical change will present a different combination of atoms, in ratio or structure.

3 0
2 years ago
The energy released in the formation of a compound from its elements is always _____ the energy required to decompose that compo
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The answer is C.Identical to
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