#4 6th grade science

Answer: A mole is a chemical unit to measure mass of substance.

Explanation:

A mole can be defined as 6.02214076 × 1023 of atoms, ions, molecules and others. A mole is the total amount of discrete entity within a substance present in the form of atoms, ions, and molecules. As atoms, ions, molecules are small entities within any substance so it is necessary to measure each of them and recognize them so the scientists development the concept of mole. It is the convenient unit of measurement because of the presence of greater number of molecules, atoms, and ions present in any substance.

Answer:

The mole is an SI unit used to measure the amount of any substance. One mole is exactly 6.02214076×10 23 particles.

Explanation:

The concept of the mole is important for scientists because it means that one mole of any element has exactly the same number of atoms as one mole of any other element. This information allows chemists to count atomic particles for even very complex chemistry formulas and reactions.

i think it is Substance C

Answer:

50 moles

Explanation:

took the quiz

Explanation:

3. the element is oxygen

pH, pOH, [H+], and [OH-] are all interrelated. For simplicity, we assume that we're working with aqueous solutions at 25 °C.

The following mathematical relations are relevant here:

A pH of 7 is neutral; a pH less than 7 is acidic; and a pH greater than 7 is basic.

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We are given four solutions of varying [H⁺], and we want to find the pH and the [OH⁻]. The pH will tell us whether the solution is neutral, an acid, or a base.

Using the relationship [H⁺] × [OH⁻] = 10^-14, we can calculate the [OH⁻] of each solution by dividing 10^-14 by the given [H⁺]:

[OH⁻] = 10^-14/(3.3 × 10^-5) = 3.0 × 10^-10

[OH⁻] = 10^-14/(4.0 × 10^-8) = 2.5 × 10^-7

[OH⁻] = 10^-14/(7.2 × 10^-11) = 1.4 × 10^-4

[OH⁻] = 10^-14/(8.2 × 10^-4) = 1.2 × 10^-11

Note: While not indicated here, the units for [H⁺] and [OH⁻] are moles/liter (M).

To find the pH of each solution, we take the negative logarithm of the [H⁺] with base 10, i.e., pH = -log₁₀[H⁺]:

pH = -log(3.3 × 10^-5) = 4.48

pH = -log(4.0 × 10^-8) = 7.40

pH = -log(7.2 × 10^-11) = 10.14

pH = -log(8.2 × 10^-4) = 3.09

Note that, for significant figures involving logarithms, the number of decimal places should equal the number of significant figures in the argument of our logarithm (the argument is what we're taking the -log of). Since we're taking the -log of quantities given to two significant figures, our corresponding pH values are given to two decimal places.

As mentioned above, a pH = 7 is neutral, a pH < 7 is acidic, and a pH > 7 is basic.

4.48 < 7, so the first solution is an acid.

7.40 > 7, so the second solution is a base.

10.14 > 7, so the third solution is a base.

3.09 < 7, so the fourth solution is an acid.

Answer:

1.) protons or electrons 2.) ion

Explanation:

Answer:

true

Explanation:

tvyvyvtvtvtbbtbb

Answer:

Rewrite the following sentence in reported speech

The chair person said,"A hearty welcome to all present!"

Answer:

76

Explanation:

Mass number = number of protons plus the number of neutrons

So, 36 + 40 = 76

Answer:

Ecosystem

Explanation:

The answer is ecosystem because the ecosystem includes the community such as living things and the enviornment of nonliving things such as the sun!

Answer:

ecosystem I'm pretty sure

Answer: [tex]H_2SO_4[/tex] is the limiting reagent.

Explanation:

A double displacement reaction is one in which exchange of ions take place. The salts which are soluble in water are designated by symbol (aq) and those which are insoluble in water and remain in solid form are represented by (s) after their chemical formulas.  

The balanced chemical equation is:

[tex]3H_2SO_4(aq)+2Al(OH)_3(aq)\rightarrow Al_2(SO_4)_3(aq)+6H_2O(l)[/tex]

To calculate the moles :

[tex]\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}[/tex]    

[tex]\text{Moles of} H_2SO_4 =\frac{30g}{98g/mol}=0.31moles[/tex]

[tex]\text{Moles of} Al(OH)_3=\frac{25g}{78g/mol}=0.32moles[/tex]  

According to stoichiometry :

3 moles of [tex]H_2SO_4[/tex] require = 2 moles of [tex]Al(OH)_3[/tex]

Thus 0.31 moles of [tex]H_2SO_4[/tex] will require=[tex]\frac{2}{3}\times 0.31=0.21moles[/tex]  of [tex]Al(OH)_3[/tex]

Thus [tex]H_2SO_4[/tex] is the limiting reagent as it limits the formation of product and [tex]Al(OH)_3[/tex] is the excess reagent.

Answer:

65.841 g

Explanation:

The balanced equation for this reaction is;

N2 + 3H2 → 2NH3  

From the question, we are interested in ammonia and the hydrogen gas.

From the equation

3 mol of H2 produces 2 mol of NH3

5.81 mol would produce x

Solving of x;

x = 5.81 * 2 / 3

x = 3.873 mol

Converting to mass;

Mass = Number of moles * molar mass

Mass =  3.873 * 17 = 65.841 g

Answer:

0.96

Explanation:

Answer: 16.32 g of [tex]O_2[/tex] as excess reagent are left.

Explanation:

To calculate the moles :

[tex]\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}[/tex]    

[tex]\text{Moles of} SO_2=\frac{21.71g}{64g/mol}=0.34mol[/tex]

[tex]\text{Moles of} O_2=\frac{21.71g}{32g/mol}=0.68mol[/tex]

[tex]2SO_2(g)+O_2(g)\rightarrow 2SO_3(g)[/tex]  

According to stoichiometry :

2 moles of [tex]SO_2[/tex] require = 1 mole of [tex]O_2[/tex]

Thus 0.34 moles of [tex]SO_2[/tex] will require=[tex]\frac{1}{2}\times 0.34=0.17moles[/tex]  of [tex]O_2[/tex]

Thus [tex]SO_2[/tex] is the limiting reagent as it limits the formation of product and [tex]O_2[/tex] is the excess reagent.

Moles of [tex]O_2[/tex] left = (0.68-0.17) mol = 0.51 mol

Mass of [tex]O_2=moles\times {\text {Molar mass}}=0.51moles\times 32g/mol=16.32g[/tex]

Thus 16.32 g of [tex]O_2[/tex] as excess reagent are left.

Answer:

C. It has no delocalised electrons and each carbon atom forms four covalent bonds with other carbon atoms.

Explanation:

The information in the first point discards options A and D, while the second point discards option B. Thus the answer is option C.

Answer:

Correct

Explanation:

According to the balanced chemical reaction, 2 mol FeBr3 are consumed for every 3 mol Na2S consumed.

A balanced equation obey the law of conservation of mass. The coefficients are the numbers which are added to balance the chemical equation. Here the given mole ratio is correct.

An equation in which the number of atoms of reactants and products on both sides of the equation are balanced is defined as the balanced chemical equation. The coefficients which are added in front of the formula of each component represents the number of the species.

A molar ratio denotes the ratio between the amounts in moles of any two compounds involved in a balanced chemical reaction. By comparing the coefficient of each component, the mole ratio can be determined.

Here for the given reaction, for every 3 moles of Na₂S consumption 2 moles of FeBr₃ is also consumed. So the molar ratio of Na₂S to FeBr₃ is 2/3. Molar ratios are used as the conversion factors between products and reactants in many chemistry problems.

To know more about mole ratio, visit;

https://brainly.com/question/29095152

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what element is A??????

Answer:Insects, such as water striders, and spiders, such as fisher spiders, can glide or scamper across the surface of water. These critters are small enough that their weight can be supported almost entirely by surface tension, the relatively weak forces that hold water molecules together.

Explanation:

Answer:

Examples of surface tension Water striders are able to walk on top of water due to a combination of several factors. Water striders use the high surface tension of water and long, hydrophobic legs to help them stay above water. Water striders use this surface tension to their advantage through their highly adapted legs and distributed weight.

Explanation:

pls mark brainliest

Answer: less oxygen available at higher altitudes

Explanation:

The higher in elevation you get, the lower the air pressure, allowing oxygen atoms to spread out farther, therefore making available oxygen less.

Answer:

10.57% of N in acetanilide

Explanation:

All nitrogen in the sample is converted in NH₃ in the Kjeldahl determination. The NH₃ reacts with H₂SO₄ as follows:

2NH₃ + H₂SO₄ → 2NH₄⁺ + SO₄²⁻

The acid in excess in titrated with Na₂CO₃ as follows:

Na₂CO₃ + H₂SO₄ → Na₂SO₄ + H₂O + CO₂

To solve this question we must find the moles of sodium carbonate = Moles of H₂SO₄ in excess. The added moles - Moles in excess = Moles of sulfuric acid that reacts:

Moles Na₂CO₃ anf Moles H₂SO₄ in excess:

0.025L * (0.05mol / L) = 1.25x10⁻³ moles Na₂CO₃ / 0.01360L =

0.09191M * 0.250L = 0.0230 moles H₂SO₄ in excess.

Moles H₂SO₄ added:

0.050L * (0.50mol / L) = 0.0250 moles H₂SO₄ added

Moles that react:

0.0250 moles - 0.0230 moles = 0.0020 moles H₂SO₄

Moles of NH₃ = Moles N:

0.0020 moles H₂SO₄ * (2mol NH₃ / 1mol H₂SO₄) = 0.0040 moles NH₃ = Moles N

mass N and mass percent:

0.0040 moles N * (14g / mol) = 0.056gN / 0.53g * 100 =

Answer:

1.Reduction

2.oxidation

Explanation:

Answer:

Reduction

Oxidation

Explanation:

Answer:

D. passing an electric current through water to form hydrogen and oxygen

Explanation:

only one that's not just a physical change.