What is the electron configuration for La (lanthanum)?

The oxidation number of Mg in Mg(OH)₂ is +2.

Hence, Option A is correct answer.

The oxidation state, or oxidation number, is defined as the hypothetical charge of an atom if all of its bonds formed with different atoms were fully ionic. It indicates the degree of oxidation of an atom in a chemical compound. Conceptually, the oxidation state may be negative, positive or zero.

Oxidation number of OH = -1

Let us suppose the oxidation number of Mg = x

Charge on compound = 0

We can write

x + 2(-1) =0

x-2=0

x = 2

Thus from the above solution we concluded that The oxidation number of Mg is +2.

Hence, Option A is correct answer.

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base

This is the answer

13 half-lives have passed

General formulas used in decay:  

[tex]\large{\boxed{\bold{N_t=N_0(\dfrac{1}{2})^{t/t\frac{1}{2} }}}[/tex]

T = duration of decay  

t 1/2 = half-life  

N₀ = the number of initial radioactive atoms  

Nt = the number of radioactive atoms left after decaying during T time  

t1/2 = 4 days

Nt=18 mg (0.01% of the original isotope)

18 mg (Nt) = 0.01% No

No = the original isotope :

[tex]\tt No=\dfrac{100}{0.01}\times 18~mg=180,000[/tex]

The duration of decay  (T) :

[tex]\tt \dfrac{Nt}{No}=\dfrac{1}{2}^{T/4}\rightarrow Nt=0.01\%No[/tex]

[tex]\tt 0.01\%=\dfrac{1}{2}^{T/4}\\\\10^{-4}=\dfrac{1}{2}^{T/4}\\\\(\dfrac{1}{2})^{13}=\dfrac{1}{2}^{T/4}\\\\13=T/4\rightarrow T=52~days[/tex]

Half-lives passed :

[tex]\tt \dfrac{52}{4}=13~half-lives[/tex]

An atom is the fundamental unit of matter and it contains an equal number of protons and electrons in its nucleus which makes it electrically neutral. An ion however, is an atom containing an unequal number of protons and electrons which means it will either carry a net positive charge or negative charge depending on whether there are more electrons or protons.

Answer:

atoms are neutral or they have equal number of proton and electron but ions can be cation(positively charged) or anion(negatively charged) based on the number of electron the atom lose and gain respectively

Answer:

1/32 of the original sample

Explanation:

edgunity got it.

The mass of He gas = 21.428 g

Given

120 liters of He gas​

Required

the mass in grams

Solution

Conditions at T 0 ° C and P 1 atm are stated by STP (Standard Temperature and Pressure). At STP, Vm is 22.4 liters/mol.

Mol for 120 L :

[tex]\tt \dfrac{120}{22.4}=5.357~moles[/tex]

Mass of He gas(MW=4 g/mol) :

[tex]\tt mass=mol\times Ar\\\\mass=5.357\times 4=21.428~g[/tex]

Answer:

C. C₆H₁₄

General Formulas and Concepts:

Chemistry - Atomic Structure

Explanation:

To find the molecular formula of the model, you simply count and add up the same elements together.

We see that we have 6 carbons and 14 hydrogens. Therefore our answer is C. C₆H₁₄

The molecule which has a structure that is most like aspirin is benzene.

Aspirin, also known as acetylsalicylic acid, is a pain reliever, fever reducer, and inflammation reducer.

In the structure of aspirin one aromatic ring is present in which carboxylic group is present and molecular formula of aspirin is written as C₉H₈O₄.

Hence benzene has a structure that is most like aspirin.

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Answer:

pH = 2.98

Explanation:

pKa of HNO2 is 3.35

HNO2 reacts with NaOH as follows:

HNO2 + NaOH → NaNO2 + H2O

Where moles of NaOH added are equal to NaNO2 produced

And initial moles of HNO2 - Moles NaOH = Moles HNO2

Initial moles HNO2:

0.0200L * (0.10mol/L) = 0.00200moles HNO2

Moles NaOH = Moles NaNO2:

0.0100L * (0.10mol/L) = 0.00100 moles NaOH = Moles NaNO2

Moles HNO2:

0.00200moles - 0.00100moles = 0.00100 moles HNO2

Then, the added HCl reacts with NaNO2 producing HNO2:

HCl + NaNO2 → HNO2 + NaCl

Where moles added of HCl are moles of HNO2 produced and initial moles  of NaNO2 - moles of HCl = Moles NaNO2

Moles HCl:

4x10⁻⁵L * (10.0mol / L) = 0.00040moles HCl = Moles of HNO2 produced

Moles HNO2:

0.00100moles + 0.0004moles = 0.0014moles HNO2

Moles NaNO2:

0.00100moles - 0.0004moles = 0.0006moles NaNO2

With these moles and H-H equation we can solve for the pH of the buffer:

pH = pKa + log [NaNO2] / [HNO2]

Where pH is pH of the buffer

pKa is pKa of HNO2: 3.35

[] are moles of each species:

Replacing:

pH = 3.35 + log [0.0006moles NaNO2] / [0.0014moles HNO2]

Answer:

The amount of work required to raise the TV from point A to point B is equal to the amount of gravitational potential energy the TV gains from its height above the ground. This is generally true for any object ...

Answer:

The answer of 1×10 -8 is 2

Answer:

Answered below

Explanation:

1) 2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)

2) 2Na (s) + H2 (g) → 2NaH (s)

3) Formula for graphite is C.

Thus;

Na + C → NaC

4) 2Na (s) + O2 (g) → 2Na_2O_2 (s)

5) 2Na (s) + Cl2 (g) → 2NaCl (s)

6) Na + Pb → NaPb

7) Na (s) + NH3 (g) → NaNH2 (s) + H2 (g)

Answer:

D

Explanation:

If there are 2 of the same rocks on two continents, that shows that they were once merged. If there is glacial existence in places where glaciers would’ve melted (Like Africa has glacial existence from Antarctica ) this shows that continents were once merged. If life forms preserved as fossils were matched on 2 different continents this shows that all the continents were once merged.

Answer:

so i am doing this and i need help what did u get for number 1

Explanation:

its the first question

Explanation:

ok that is ans k............

The temperature of the 20 L tank containing 68 g of carbon dioxide, CO₂ at 500 KPa is 778.5 K

Mole = mass / molar mass

Mole of CO₂ = 68 / 44

Mole of CO₂ = 1.545 moles

Using the ideal gas equation, the temperature of the gas can be obtained as follow:

PV = nRT

Divide both side by nR

T = PV / nR

T = (500 × 20) / (1.545 × 8.314)

T = 778.5 K

Thus, the temperature of the tank is 778.5 K

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Answer:

cesium is the largest alkali metal.

Explanation:

Answer:

Cesium

Explanation:

Cesium is the largest atom among alkali metal.

Answer:52M

Explanation:

use S= 1000w/ MV

Here, s= molarity

w= the amount of NaCl

M= the atomic mass of NaCl

V= the volume of solution

Answer:

B

Explanation:

Answer:

D

Explanation:

Because if I said its 35 degrees outside that has nothing to do with climate maybe if I said its usually 35 degrees in the month of December but just saying what temperature it doesn't tell you anything about climate

Well, the definition of climate is the weather conditions prevailing in an area in general or over a long period so I don't really know

So maybe it is d

Answer:

B

Explanation:

Weather refers to the short-term conditions of the lower atmosphere, such as precipitation, temperature, humidity, wind direction, wind speed, and atmospheric pressure. It could be sunny, cloudy, rainy, foggy, cold, hot, windy, stormy, snowing … the list goes on.

Answer:

1. Pollution caused the bark to become darker.

2. The light-colored peppered moth had a higher chance of survival

3. The dark-colored peppered moth had a higher chance of survival

4. During the Industrial Revolution, the barks of trees got darks, causing the moths to be seen easily on a dark background. Now predators were more likely to eat the lighter cloured moths as they were easier to find. Since fewer light-colored moths were surviving, there was a smaller likelihood of light moths surviving long enough to reproduce. Since there were fewer light-colored moths, the dark-colored moths had less competition and were able to reproduce quickly.

5. Sunny, warm place: I live in a place with lots of light and sunshine, so it would be easier for light moths to blend in with their environment long enough to reproduce and thrive.

Dark, rainy Place: I live in a place with little light and sunshine, so it would be easier for dark moths to blend in with their environment long enough to reproduce and thrive.

Explanation:

Answer:

The answer would be cation

Explanation:

Answer:

it's an anion

if it has more electrons than protons, then it has a negative net charge making it an anion

Answer:

0.6022×10²³ molecules

Number of moles = 0.1 mol

Explanation:

Given data:

Mass of HCl = 3.65 g

Number of molecules = ?

Number of moles = ?

Solution:

Number of moles:

Number of moles = mass/molar mass

Number of moles = 3.65 g/36.45 g/mol

Number of moles = 0.1 mol

Number of molecules:

1 mole of any substance contain 6.022×10²³ molecules

0.1 mol ×  6.022×10²³ molecules/ 1 mol

0.6022×10²³ molecules

Answer:

molecular formulas of the hydrocarbons

Answer:

coh3 and xxxxxxxxxxxxx

Answer:

B

Explanation:

CH4 + 2 O2 → CO2 + 2 H20

12 + I X 4 → → 2 ( I X2 + 16 )

16 → → 36

25, 5 → → ?

amount of H2O = 36 X 25,5 / 16 = 57. 39

One mole or 16 g of methane gas reacts with excess oxygen to give 2 moles or 36 g of water. Then, the mass of water produced from 25.5 g of methane is 57.3 g.

Combustion is the reaction of a gas with the atmospheric oxygen producing water and carbon dioxide. The hydrocarbon gases such as methane, ethane etc easily undergo combustion reaction.

As per the given balanced reaction, one mole of methane gas CH4 produces two moles of water.

molar mass of methane = 16 g/mol

molar mass of water = 18 g/mol

mass of 2 moles of water = 36 g.

Hence, 16 g methane gas produce 36 g of water.

The mass of water produced from 25.5 grams of methane gas is then calculated as follows:

mass of water = 25.5 × 36 / 16 = 57.3 g.

Therefore, 57.3 g of water is produced in this reaction from 25.5 g of methane.

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Answer:

atoms

Explanation:

atoms combines to form compound

Answer:Multiple the moles of Na2 SO4 that you found just

Explanation:

Ions are formed by gaining and donating the valence electrons from the outer shells. Sodium has an extra electron and forms cations. In 1.5 grams of Na⁺, there are 0.0652 moles ions.

Cations are said to be the ions that are formed by donating electrons from their valence shell. They tend to donate their electrons to form ionic bonds with another atom that accepts the electrons.

The mass and the molar mass of the cation can be used to calculate the number of moles contained in the atom or the ion.

Given,

Mass of sodium ions = 1.50 grams

The molar mass of sodium ions = 22.98 amu

The number of moles of sodium cation is calculated as:

Moles (n) = mass ÷ molar mass

n = 1.50 ÷ 22.98

= 0.0652 moles

Therefore, 0.0652 moles are present in 1.50 grams of sodium ions.

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Answer:

17 for chlorine atom ; 18 electrons for a chlorine ion

Explanation:

giving equal opportunity,making good governance, maintaining peace and harmony among people, other try to write by your self