which of these elements has two valence electrons?

a. hydrogen (H)
b. barium (Ba)
c. nitrogen (N)
d. krypton (Kr)
e. bromine (Br)​

Answer:

The change in concentration of H+ ions is -9.99×10⁻⁵

Explanation:

When pH rises, we talk about neutralization and, there is a decline in proton's concentration.

pH lower than 7 is acid

pH higher than 7 is basic

Protons are neutralized by hydroxides to make water as this:

H₃O⁺   +  OH⁻  ⇄   H₂O

pH = - log [H₃O⁺]

[H₃O⁺] = 10^-pH

In conclussion: [H₃O⁺]₁ = 10⁻⁴ → 1×10⁻⁴

[H₃O⁺]₂ = 10⁻⁷ → 1×10⁻⁷

1×10⁻⁷- 1×10⁻⁴

The change in concentration of H+ ions is -9.99×10⁻⁵

Answer:

Explanation:

The percentage error of a certain measurement can be found by using the formula

[tex]P(\%) = \frac{error}{actual \: \: number} \times 100\% \\ [/tex]

From the question

actual density = 7.80 g/cm³

error = 7.30 - 7.80 = 0.5

We have

[tex]p(\%) = \frac{0.5}{7.8} \times 100 \\ = 6.410256...[/tex]

We have the final answer as

Hope this helps you

Answer:

so in one mole of atom there are 6.02×10^23.

answers to B is 2.41×10^24

Explanation:

use this equation

number of particle=moles X 6.02×10^23

=4 X 6.02 ×10^23

=2.41×10^24

hope this make sense:)

The number of particles present in 4 moles of a substance is 24.088 particles.

Moles is a unit to express the amount of any substance and in one mole of any substance 6.022 × 10²³ particles of that substance are present and this number is known as Avogadro's number.

As in 1 mole = 6.022 × 10²³ particles are present

In 4 moles = 4 × 6.022 × 10²³ = 24.088 particles are present

Hence, 24.088 particles are present in 4 moles.

To know more about Avogadro's number, visit the below link:
https://brainly.com/question/10614569

Answer:

See explanation

Explanation:

The functional group is an atom, group of atoms or bond which is responsible for the chemical reactions of the members of a series of organic compounds.

The chemical properties of various groups of compounds in organic chemistry depends of the concept of functional groups. They help us to classify molecules into families or groups based on a common general molecular formula.

The nature of the functional group determines the overall chemical properties of the molecule such as polarity, water solubility, and so on. Chemical reactions occur only at the functional group.

For instance, for the reaction below, reaction occurs at the functional groups as follows;

CH3COOH + CH3OH -------> CH3COOCH3

Also, during amide formation, reaction occurs between the carbonyl chloride and an amine at the respective functional groups as shown;

CH3COCl + CH3NH2 -----> CH3CONHCH3 + HCl

Answer:

lead causes vessels to constrict, limiting the space for blood to flow (compare the size of the red circles.) This narrowing increases blood pressure, forcing the heart to work harder.

Answer:

By mimicking calcium and increasing cell stress, lead causes vessels to constrict, limiting the space for blood to flow. This forces the heart to work harder because the narrowing increases blood pressure.

Answer:

The boiling point of heavy water is 101.4C

please mark me brainlest pls

Answer: 101.42 Celsius

Explanation:

The boiling point of heavy water is 101.42 Celsius which is higher than the boiling point of normal water (100 Celsius)due to its higher molar mass

The carbons on either side of the double bond are pointed in opposite directions.

Answer:

333.3mL

Explanation:

Using the formula as follows:

C1V1 = C2V2

Where;

C1 = initial concentration (M)

C2 = final concentration (M)

V1 = initial volume (mL)

V2 = final volume (mL)

According to the information provided in this question,

C1 = 4.00M

C2 = 1.50M

V1 = 125mL

V2 = ?

Using C1V1 = C2V2

4 × 125 = 1.5 × V2

500 = 1.5V2

V2 = 500/1.5

V2 = 333.3mL

Therefore, the CuSO4 solution needs to be diluted to 333.3mL to make 1.50 M solution.

Answer:

In a physical change the appearance or form of the matter changes but the kind of matter in the substance does not. However in a chemical change, the kind of matter changes and at least one new substance with new properties is formed. The distinction between physical and chemical change is not clear cut.

Answer:

B) 0.211 M

Explanation:

Answer:

The products from the neutralization reaction are barium nitrate and water.  

The balanced chemical equation is

2 [tex]HNO_{3}[/tex] +  1 [tex]Ba(OH)_{2}[/tex]  -->  1 [tex]Ba(NO_3)_{2}[/tex] +  2 [tex]H_{2}O[/tex].  

potassium reacts the most vigorously.

Answer:

c. 0.37 moles

Explanation:

To find the number of moles (n) in a certain number of atoms of a substance, we divide the number of atoms by Avogadro number (nA), which is 6.02 × 10²³ atoms.

That is,

n = number of atoms ÷ 6.02 × 10²³

According to this question, there are 2.25 x 10²³ atoms of carbon (C). The number of moles contained in this carbon is as follows:

n = 2.25 x 10²³ ÷ 6.02 × 10²³

n = 2.25/6.02 × 10 (23 - 23)

n = 0.374 × 1

n = 0.374moles

Answer:

Ozone layer depletion is the thinning of the ozone layer present in the upper atmosphere. This happens when the chlorine and bromine atoms in the atmosphere come in contact with ozone and destroy the ozone molecules. One chlorine can destroy 100,000 molecules of ozone. It is destroyed more quickly than it is created

Answer:

Ozone depletion, gradual thinning of Earth’s ozone layer in the upper atmosphere caused by the release of chemical compounds containing gaseous chlorine or bromine from industry and other human activities. The thinning is most pronounced in the polar regions, especially over Antarctica. Ozone depletion is a major environmental problem because it increases the amount of ultraviolet (UV) radiation that reaches Earth’s surface, which increases the rate of skin cancer, eye cataracts, and genetic and immune system damage. The Montreal Protocol, ratified in 1987, was the first of several comprehensive international agreements enacted to halt the production and use of ozone-depleting chemicals. As a result of continued international cooperation on this issue, the ozone layer is expected to recover over time.

Answer:

im not entirely sure what needs to be done but the 2NH3 is the product and the other half is the reactants .

if any elements are added to others it is the reactants

this is a breakdown of a compound because the arrow always indicates the direction of the reaction .

Answer:

the third one...........

Answer:

wax melting off a candle

Answer:

The answer is SiO2

Explanation:

Because nonmetals are those who gain electrons and form ve ions

Answer:

Because iodine is a liquid, it has no melting point. Iodine is not an electrical conductor because each molecule consists of two iodine atoms connected by a covalent bond that cannot be stimulated sufficiently to transmit electrical energy.

Explanation:

brainlist???

Explanation:

Because in an aqueous solution of iodine, iodine atoms are joined to each other by simple covalent bonds. Thus, when excitation occurs, the strength of the covalent bond is too weak to be able to transfer electrons, thus lacking the ability to conduct electricity.

Answer:

Metals:

1. Metals are strong than non metals

2. Metals can be formed in wires, thin sheets, utensils and any other heavy meachinary for industries.

3. Metals are used for building construction and used in many other manufacturers

Non Metals:

1. Non metals are less stronger than metals.

2. Non metals can be used for manufacturing bottles, toys, bags, files etc.

3. Non metals are used in making of bottles, jars, chairs etc.

Thank you.....

Have a good day.....

Answer:

A. 31.0

Explanation:

Remember the formula [tex]Density = \frac{mass}{Volume}[/tex], or [tex]D=\frac{m}{V}[/tex].

The problem tells us that the density is 1.89 g/L, and that the volume is 16.4 L.(Remember that if the units are in some form of liters, it is volume, similar to how if the units are in grams, it is mass.)

Plug in the numbers for density and volume, and you will get:

[tex]1.89=\frac{m}{16.4}[/tex]

Then, multiply both sides by 16.4 to get:

m = 30.996 g ≈ 31.0 g

Hope this helps!

Answer: The number of moles of excess reagent left is 0.750 moles

Explanation:

The number of moles is calculated by using the equation:

[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex] ......(1)

Given mass of [tex]KI[/tex] = 249 g

Molar mass of [tex]KI[/tex] = 166 g/mol

Putting values in equation 1, we get:

[tex]\text{Moles of KI}=\frac{249g}{166g/mol}=1.5mol[/tex]

Given mass of [tex]Pb(NO_3)_2[/tex] = 496.5 g

Molar mass of [tex]Pb(NO_3)_2[/tex] = 331 g/mol

Putting values in equation 1, we get:

[tex]\text{Moles of }Pb(NO_3)_2=\frac{496.5g}{331g/mol}=1.5mol[/tex]

The given chemical equation follows:

[tex]2KI+Pb(NO_3)_2\rightarrow 2KNO_3+PbI_2[/tex]

By stoichiometry of the reaction:

If 2 moles of KI reacts with 1 mole of lead(II) nitrate

So, 1.5 moles of KI will react with = [tex]\frac{1}{2}\times 1.5=0.75mol[/tex] of lead(II) nitrate

As the given amount of lead(II) nitrate is more than the required amount. Thus, it is present in excess and is considered as an excess reagent.

Thus, KI is considered a limiting reagent because it limits the formation of the product.

Moles of excess reactant ([tex]Pb(NO_3)_2[/tex]) left = [1.5 - 0.75] = 0.750 moles

Hence, the number of moles of excess reagent left is 0.750 moles

Answer:

20.25 W

Explanation:

Applying,

P = I²R.................... Equation 1

Where P = Power, I = current drawn by the test light, R = Resistance of the test light

From the question,

Given: I = 1.5 A, R = 9.00 Ω

Substitute these values into equation 1

P = (1.5²)(9)

P = 2.25×9

P = 20.25 W

Answer:

the anwer is glycolysis

Answer:

Sugar was the solute and water was the solvent.

Answer:

1. 43.44g of HCl

2. 26.67 L of HCl

Explanation:

1) Molarity of a solution = number of moles (n) ÷ Volume (V)

According to the provided information in this question,

V = 350 mL = 350/1000 = 0.350L

Molarity = 3.4 M

Using Molarity = n/V

3.4 = n/0.350

n = 3.4 × 0.350

n = 1.19mol

Using the formula below to calculate the mass of HCl;

mole = mass/molar mass

Molar mass of HCl = 1 + 35.5 = 36.5g/mol

mole = mass/MM

mass = 1.19 mol × 36.5g/mol

mass = 43.44g of HCl

2) At STP, HCl has a pressure of 1atm, a temperature of 273K

V = ?

n = 1.19 mol

R = 0.0821 Latm/molK

Using PV = nRT

V = nRT/P

V = 1.19 × 0.0821 × 273/1

Volume = 26.67L

Answer:

B

Explanation:

B

Answer:

The correct option is 2.

Explanation:

In a nuclear reaction balanced we have that:

1. The sum of the mass number (A) of the reactants (r) is equal to the sum of the mass number of the products (p) [tex] \Sigma A_{r} = \Sigma A_{p} [/tex]

2. The sum of the atomic number (Z) of the reactants is also equal to the sum of the atomic number of the products [tex]\Sigma Z_{r} = \Sigma A_{p}[/tex]      

So, let's evaluate each option.

1) [tex]^{23}_{11}Na \rightarrow ^{24}_{11}Mg + ^{1}_{1}H[/tex]

The mass number of the reactant is:

[tex]A_{r} = 23 [/tex]

The sum of the mass number of the products is:

[tex] A_{p} = 24 + 1 = 25 [/tex]

This is not the correct option because it does not meet the first condition ([tex] \Sigma A_{r} = \Sigma A_{p}[/tex]).

2) [tex]^{24}_{11}Na \rightarrow ^{24}_{12}Mg + ^{0}_{-1}e[/tex]  

The mass number of the reactant and the products is:

[tex]A_{r} = 24 [/tex]

[tex] A_{p} = 24 + 0 = 24 [/tex]

Now, the atomic number of the reactants and the products are:

[tex]Z_{r} = 11 [/tex]

[tex] Z_{p} = 12 + (-1) = 11 [/tex]      

This nuclear reaction is balanced since it does meet the two conditions for a balanced nuclear equation, ([tex] \Sigma A_{r} = \Sigma A_{p}[/tex] and [tex] \Sigma Z_{r} = \Sigma Z_{p}[/tex]).  

3) [tex]^{24}_{13}Al \rightarrow ^{24}_{12}Mg + ^{0}_{-1}e[/tex]      

The mass number of the reactant and the products is:

[tex]A_{r} = 24 [/tex]

[tex] A_{p} = 24 + 0 = 24 [/tex]

Now, the atomic number of the reactants and the products are:

[tex]Z_{r} = 13 [/tex]

[tex] Z_{p} = 12 + (-1) = 11 [/tex]      

This reaction does not meet the second condition ([tex] \Sigma Z_{r} = \Sigma Z_{p}[/tex]) so this is not a balanced nuclear equation.

4) [tex]^{23}_{12}Mg \rightarrow ^{24}_{12}Mg + ^{1}_{0}n[/tex]

The mass number of the reactant and the products is:

[tex]A_{r} = 23 [/tex]

[tex] A_{p} = 24 + 1 = 25 [/tex]  

This reaction is not a balanced nuclear equation since it does not meet the first condition ([tex] \Sigma A_{r} = \Sigma A_{p}[/tex]).

Therefore, the correct option is 2.

I hope it helps you!

Answer:

pure

Explanation:

because there no additional substance