Suppose you need to prepare 250.0 mL of a pH=3.60 buffer that has a total buffer concentration of formic acid + formate of 0.030 M. How many moles of formic acid will you need? The pKa of formic acid is 3.75.

Answer:

Isotopes are variants of an element, where the number of neutrons is different but its number of protons stay the same.

Explanation:

If the number of protons had changed then it would just be a different element.

Electron number changing simply adds charge to the atom, and doesn't change it or anything.

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Answer:

Isotopes are one of two or more forms of the same chemical element.

Explanation:

Different isotopes of an element have the same number of protons in the nucleus, giving them the same atomic number,but a different number of neutrons giving each element isotope of a different atomic weight.

Answer:

39.1-32.5 and you will find your answer it always like that, you subtract your starting point from your ending point

Explanation:

The volume of the piece of lead is 6.6 mL

From the question given above, the following data were obtained:

The volume of the lead can be obtained as follow:

Volume of lead = (Volume of water + Lead) – (Volume of water)

Volume of lead = 39.1 – 32.5

Volume of lead = 6.6 mL

Therefore the volume of the lead is 6.6 mL

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Answer:

The Universe is constantly expanding and as it expands the stars and objects in space move farther apart, just like the points on the balloon when air is blown into it. Density and distribution of "stars" as the balloon expands because when volume increases the density will increase.

Hope this Helps

Answer:

Explanation:

The number of S atoms can be found by using the formula

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question we have

N = 0.67 × 6.02 × 10²³

We have the final answer as

Hope this helps you

Answer:

Because elements cannot decompose

Explanation:

Elements are distinct substances that cannot be split-up into simpler substances. Such substances are only made up of one atom.

Question: How many atoms of sodium (Na) are there on either side of the equation?

Options: A) one B) two C) four D) six

Correct answer: D) six

Answer:

It is NOT six, i took the test and got it wrong. The CORRECT answer is 2

Explanation:

Answer:

m = 0.00659 kg = 6.59 g

Explanation:

From Faraday's Law of Electrolysis, we know that:

m = ZQ

where,

m = mass of silver deposited = ?

Q = charge supplied = (1.65 A-hr)(3600 s/1 hr) = 5940 C

Z = electrochemical equivalent of silver = 1.18 x 10⁻⁶ kg/C

Therefore,

m = (1.11 x 10⁻⁶ kg/C)(5940 C)

m = 0.00659 kg = 6.59 g

The mass of silver that would be deposited by a battery is 6.65 grams

The precipitation of Ag requires the removal of one electron. The reduction process for silver electrode at the cathode is as follows:

[tex]\mathbf{Ag^+ + e^- \to Ag(s)}[/tex]

∴

In one mole of an electron, the charge carried = 96500 C

Recall that:

The atomic mass of silver (Ag) = 108 g

∴

The mass of silver that would be deposited in a 5940 C can be computed as:

[tex]\mathbf{=5940\ C \times \dfrac{108 \ g }{96500 \ C}}[/tex]

= 6.65 grams

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Answer:

1.45 Atmospheres = 146.92125 Kilopascals, or about 146.9 Kilopascals

Explanation:

1 Atmosphere = 101.325 Kilopascals, so 101.325 Kilopascals x 1.45 Atmospheres = 146.92125 Kilopascals.

Using the conversion table, the pressure of the compressed gas at 1.45 atm when converted to kilopascal becomes 146.92 kPa.

Atm is the standard atmosphere which is a unit of pressure.

From conversion table

1 atm atmospheric pressure is equivalent to 101.325 kPa ( kilopascal ).

Now, the pressure of the compressed gas at 1.45 atm will be;

P = 1.45 × 101.325 kPa

P = 146.92 kPa

Therefore, the pressure of the compressed gas at 1.45 atm when converted to kilopascal using the conversion table becomes 146.92 kPa.

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Answer:

Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen.

Answer: 0.217 mol

Explanation:

To find the amount of moles in a 10 g sample, we need the molar mass of ethanol.

Molar Mass: 46.07 g/mol

Now that we have the molar mass, we can find moles.

[tex]10.0 g*\frac{1mol}{46.07g}=0.217 mol[/tex]

We know that there are 0.217 mol in a 10.0 gram sample.

The ions are able to move freely from one place to another. So that they conduct electricity. But the molecular solutions does not electricity.

The molecular solution is composed of molecules and consists of non - metallic atoms. These atoms are held together by the covalent bonds. The flow of charged particles is responsible for the conduction of electricity. If there is no flow of electrons or ions then there will be no electricity.

In the molecular solutions, the molecules present are not dissociated into respective ions. Since the molecules are not converted into the charged particles no electricity is produced.

A molecular solution is regarded as a non-electrolyte which does not contain ions. But electrolytes are dissociated into ions and thereby conducts electricity. So all electrolytes are good conductors of electricity.

Thus molecular solution does not contain ions.

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Answer:

Partial pressure of neon = 175 mmHg

Partial pressure of xenon = 564 mmHg

Explanation:

The partial pressure of a gas in a mixture can be calculated as the product of the mole fraction of the gas (Xi) and the total pressure (Pt), as follows:

Pi = Xi Pt

The total pressure is 739 mmHg ⇒ Pt =  739 mmHg

In order to calculate the mole fraction of each gas, we have to first calculate the number of moles of each gas (n) by dividing the mass of the gas into the molar mass (MM):

For neon gas (Ne):

MM(Ne) = 20.18 g/mol

n(Ne)= mass/MM = 0.919 g x 1 mol/20.18 g = 0.045 mol Ne

For xenon gas (Xe):

MM(Xe) = 131.3 g/mol

n(Xe)= mass/MM = 19.1 g x 1 mol/131.3 g = 0.145 mol Xe

Now, we calculate the mole fraction (X) by dividing the number of moles of the gas into the total number of moles (nt):

nt= moles Ne + moles Xe = 0.045 mol + 0.145 mol = 0.190 mol

X(Ne) = moles Ne/nt = 0.045 mol/0.190 mol = 0.237

X(Xe) = moles Xe/nt = 0.145/0.190 mol = 0.763

Finally, we calculate the partial pressures of Ne and Xe as follows:

P(Ne) = X(Ne) x Pt = 0.237 x 739 mmHg = 175 mmHg

P(Xe) = X(Xe) x Pt = 0.763 x 739 mmHg = 564 mmHg

Answer:

D

Explanation:

it is trigonal planar, because central atom does not have the lone pairs, equal repulsion

The molecular geometry of the central atom in ClO3- will be triangular pyramidal.

The geometry of molecular structures can be predicted using the chemical model known as the valence shell electron pair repulsion hypothesis based on the number of electron pairs surrounding the core atoms of the molecules.

Since ClO3- has a steric number of 4 (one unpaired pair as well as three bonded pairs), can infer that its molecular shape is triangular pyramidal. Its electrical form is tetrahedral, as shown by the Lewis structure above.

Therefore, the correct answer will be option (c).

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Answer:

C

Explanation:

Al=Aluminum

Mg=Magnesium

Answer:

the density of CO2 gas at STP is 1.96 g/l.

Answer:

oxygen, silicon, iron, calcium, sodium

Explanation:

these are all found in space rocks known as meteorites. hope this helps :)

Answer:

A chemical reaction is the process in which atoms present in the starting substances rearrange to give new chemical combinations present in the substances formed by the reaction. These starting substances of a chemical reaction are called the reactants, and the new substances that result are called the products.

Answer: 51.9961 g/mol, don't know if it helps :)

Explanation:

Answer:

Chromium is a steel-gray, lustrous, hard metal that takes a high polish, is fusible with difficulty, and is resistant to corrosion and tarnishing.

The most common oxidation states of chromium are +2, +3, and +6, with +3 being the most stable. +4 and +5 are relatively rare. Chromium compounds of oxidation state 6 are powerful oxidants.ion:

Answer:

Volume of water added = 148.4 mL

Explanation:

Given data:

Initial volume = 424 mL

Initial molarity = 0.189 M

Final molarity = 0.140 M

Volume of water added = ?

Solution:

Formula:

M₁V₁  =   M₂V₂

0.189 M×424 mL = 0.140 M×V₂

V₂ = 0.189 M×424 mL /0.140 M

V₂ = 80.136 M.mL / 0.140 M

V₂ = 572.4 mL

Final volume of solution is  572.4 mL.

Volume of water added = Final volume - initial volume

Volume of water added = 572.4 mL - 424 mL

Volume of water added = 148.4 mL

Answer:

B- beaker

Explanation:

..............

Answer:

Atoms in group 2a are likely to form ions with a +2 charge because they have two valence electrons, both of which experience a very weak pull from the nucleus due to electron shielding. This causes the atoms to be easily pulled away from the nucleus, creating the +2 ions we see in nature.

Atoms in group 7a are likely to form ions with a -1 charge because they are one electron away from completing their outermost shell. The large number of protons in the middle of these atoms also causes the valence electrons to experience a stronger net force. This force also pulls strongly on the valence electrons of other atoms, causing the -1 ions we see in nature.

Answer:

Explanation:

1) Pure substance: Water (found at home)

Appearance: It is homogeneous since it is a single substance that appears as liquid. Homogeneous is when the components of a substance are in a single phase

Separating technique: It's component cannot be separated by physical means

Boiling point: Water boils at 100 °C

Melting point: Water melts/freezes at 0°C

2) Pure substance: Table salt (found at home)

Appearance: It is also homogeneous as it is a single substance that is solid. Separating technique: It's component cannot be separated by physical means

Boiling point: Water boils at 1,465 °C

Melting point: Water melts/freezes at 801 °C

3) Pure substance: Butter (found at home and grocery store)

Appearance: It is homogeneous even though it contains different components

Separating technique: It's component can be separated by physical means since butter is an emulsion of fat in water. The 15% water content can be evaporated/distilled out at 100 °C

Boiling point: Butter starts boiling at about 110-120 °C

Melting point: It melts at about 37 °C

4) Pure substance: Candle (wax) (found at home and grocery store)

Appearance: It is homogeneous

Separating technique: It's component cannot be separated by physical means

Boiling point: It starts boiling around 370 °C

Melting point: It melts at about 37 °C

5) Pure substance: table sugar/sucrose (found at home, grocery stores and in supermarkets)

Appearance: It is homogeneous

Separating technique: It's component cannot be separated by physical means

Boiling point: It starts boiling around 697 °C

Melting point: It melts at about 186 °C

A pure substance is an homogeneous material, having a composition, and

properties that are consistent through out the material.

The chemical properties of a pure substance are defined, such as the

products of its reaction can be predictable.

A chemical is pure when it consist of a single type of particle such as an

element, a molecule or a compound.

The five pure substances are presented as follows;

[tex]\displaystyle\begin{tabular}{|l|l|l|l|l|}\underline{Pure \ Substances}&\underline{Appearance}&\underline{Separaing Tech}&\underline{Boiling \ Point}&\underline{Melting \ point}\\1. Diamond&Translucent \ solid&Inseparable&3550^{\circ}&4830^{\circ}\\2. Table \ salt&White\ crystals&Insepble&801^{\circ}&1413^{\circ}\\3. Water&Tran parent \ liquid&Insepble&0^{\circ}&100^{\circ}\\4. Sugar&Whilte \ crystals&Heating&Decomposes&186^{\circ}\\5. Gold&Yellowish \ metal&Inseparable& 2700^{\circ}&1064^{\circ}\end{array}[/tex]

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Answer:

Antoine Lavoisier

1) Law of Conservation of Mass

French chemist, Antoine Lavoisier in 1789, studied this law. This law states that “In all physical and chemical changes, the total mass of the reactants is equal to that of the products” or “Mass can neither be created nor destroyed.”

Answer:

ΔH= -390.3kJ

Explanation:

Using Hess's law, we can obtain ΔHrxn from the sum of related reactions.

Using:

(1) C(s) + 2H2(g) → CH4(g) ΔH=−74.6kJ

(2) C(s) + 2Cl2(g) → CCl4(g) ΔH=−95.7kJ

(3) H2(g) + Cl2(g) → 2HCl(g) ΔH=−184.6kJ

(2) - (1):

CH4(g) + C(s) + 2Cl2(g) → CCl4(g) + C(s) + 2H2(g)

CH4(g) + 2Cl2(g) → CCl4(g) + 2H2(g)

ΔH= -95.7kJ - (-74.6kJ) = -21.1kJ

This reaction + 2*(3):

2H2(g) + 2Cl2(g) + CH4(g) + 2Cl2(g) → CCl4(g) + 2H2(g) +4HCl(g)

CH4(g) + 4Cl2(g) → CCl4(g) + 4HCl(g)

ΔH= -21.1kJ + 2*-184.6kJ

The number of mole of NaCl needed to react with excess Pb²⁺ to produce 45.5 g of PbCl₂ is 0.328 mole

We'll begin by calculating the number of mole in 45.5 g of PbCl₂. This can be obtained as follow:

Mass of PbCl₂ = 45.5 g

Molar mass of PbCl₂ = 207 + (35.5×2) = 278 g/mol

Mole = mass / molar mass

Mole of PbCl₂ = 45.5 / 278

2NaCl + Pb²⁺ —> PbCl₂ + 2Na⁺

From the balanced equation above,

2 moles of NaCl reacted to produce 1 mole of PbCl₂

Therefore,

Xmol of NaCl will react to produce 0.164 mole of PbCl₂ i.e

Xmol of NaCl = 2 × 0.164

Xmol of NaCl = 0.328 mole

Thus, the number of mole of NaCl needed for the reaction is 0.328 mole

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Answer:

[tex]\% Fe=48.2\%[/tex]

Explanation:

Hello!

In this case, since the percent composition of an element in a compound is given by:

[tex]\% i =\frac{z_i*m_i}{MM}*100\%[/tex]

Whereas i represent the element in the compound for which we want compute the mass percent. As required for siderite, FeCO3 whose molar mass is 115.854 g/mol, and knowing there is one iron atom there with an atomic mass od 55.85 g/mol, the mass percent of iron there is:

[tex]\% Fe=\frac{1*55.85}{115.854}*100\%\\\\\% Fe=48.2\%[/tex]

Best regards!

Copper is higher than silver in the electrochemical series hence copper displaces silver in the electrochemical series.

The solubility of a metal in another is determined by their relative positions in the electrochemical series. The metals that are higher above in the electrochemical series displaces the metals that are lower in the electrochemical series.

Copper is higher than silver in the electrochemical series hence copper displaces silver in the electrochemical series. Therefore, the correct explanation for an observation is that;

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Answer:

Observation 1 is a result of copper ions moving into the solution.

Explanation:

got it right on the test