CHEMISTRY MIDDLE SCHOOL

If a cell is like a city, then city hall, or the control center, would be the cell's ___________.

Answers

Answer 1

Answer:

Answer: Nucleus. the nucleus has control over the whole cell.

Answer 2

Answer:

Answer: Nucleus

Explanation:

The cell’s nucleus is what controls all of the cell’s functions, therefore similar to how a city hall controls a city’s functions.

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Radio waves have the lowest energies, longest wavelengths, and lowest frequencies of any type of EM radiation.

What is a good sentence for the word orbit?

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1. What is the volume of 0.900 moles of an ideal gas at 25.0° C and a pressure of 950.0 mm Hg?1.50 liters
17.6 liters
18.0 liters
34.2 liters

2. What is the pressure, in mm Hg, of 2.50 moles of an ideal gas if it has a volume of 50.0 liters when the temperature is 27.0° C?
84.2 mm Hg
289 mm Hg
617 mm Hg
936 mm Hg

3. When 12.4 grams of KBr are dissolved in enough water to create a 170-gram solution, what is the solution's concentration, expressed as a percent by mass?
6.2% KBr
6.8% KBr
7.3% KBr
7.9% KBr

Answers

1. Using the ideal gas law, which states that PV = nRT, and remembering that absolute temperature must be used:
(950.0 mmHg)(V) = (0.900 moles)(R)(25.0 + 273.15 K)
The most convenient value of R is 0.08206 L-atm/mol-K, so we convert the pressure of 950.0 mmHg to atm by dividing by 760: 1.25 atm
(1.25 atm)(V) = (0.9)(0.08206)(298.15)
V = 17.6 L

2. Again using the ideal gas law, and converting temperature to Kelvin: 27 + 273.15 = 300.15 K
PV = nRT
P(50.0 L) = (2.50 moles)(0.08206 L-atm/mol-K)(300.15 K)
P = 1.23 atm
Then we multiply by 760 mmHg / 1 atm = 936 mmHg. This is the fourth of the choices.

3. If the complete solution has a mass of 170 grams, and 12.4 grams of it is the dissolved KBr, we simply have to divide the mass of solute (KBr) by the total mass of the solution: This gives us 12.4 grams / 170 grams = 0.0729. Multiplying by 100% gives 7.29% or approximately 7.3% KBr, which is the third of the choices.

1. The volume of the ideal gas is $\boxed{{\text{17}}{\text{.6 L}}}$ .

2. The pressure of the ideal gas is $\boxed{{\text{936 mm Hg}}}$ .

3. The concentration of the solution, expressed as mass percent is $\boxed{{\text{7}}{\text{.3 \% }}}$ .

Further Explanation:

An ideal gas is a hypothetical gas that is composed of a large number of randomly moving particles that are supposed to have perfectly elastic collisions among themselves. It is just a theoretical concept and practically no such gas exists. But gases tend to behave almost ideally at a higher temperature and lower pressure.

Ideal gas law is the equation of state for any hypothetical gas. The expression for the ideal gas equation is as follows:

${\text{PV}} = {\text{nRT}}$ .......(1)

Here,

P is the pressure of ideal gas.

V is the volume of ideal gas.

T is the absolute temperature of the ideal gas.

n is the number of moles of the ideal gas.

R is the universal gas constant.

1. Rearrange equation (1) to calculate the volume of the ideal gas.

${\text{V}}=\frac{{{\text{nRT}}}}{{\text{P}}}$ ......(2)

The pressure of the ideal gas is 950 mm Hg.

The temperature of the ideal gas is ${\text{25}}\;^\circ{\text{C}}$ .

The number of moles of the ideal gas is 0.9 mol.

The universal gas constant is 0.0821 L atm/K mol.

Substitute these values in equation (2).

$\begin{aligned}{\text{V}}&=\frac{{\left( {{\text{0}}{\text{.9 mol}}} \right)\left( {0.0821{\text{ L atm/K mol}}} \right)\left( {25 + 27{\text{3}}{\text{.15}}}\right){\text{K}}}}{{\left( {950{\text{ mm Hg}}}\right)\left( {\frac{{{\text{1 atm}}}}{{760{\text{ mm Hg}}}}}\right)}}\n&= 17.624{\text{ L}}\n&\approx {\text{17}}{\text{.6 L}}\n\end{aligned}$

Therefore the volume of the ideal gas is 17.6 L.

2. Rearrange equation (1) to calculate the pressure of ideal gas.

${\text{P}} =\frac{{{\text{nRT}}}}{{\text{V}}}$ ......(3)

The volume of the ideal gas is 50 L.

The temperature of the ideal gas is ${\text{27}}\;^\circ {\text{C}}$ .

The number of moles of the ideal gas is 2.5 mol.

The universal gas constant is 0.0821 L atm/K mol

Substitute these values in equation (3).

$\begin{aligned}{\text{P}}&= \frac{{\left( {{\text{2}}{\text{.5 mol}}} \right)\left( {0.0821{\text{ L atm/K mol}}} \right)\left( {27 + 27{\text{3}}{\text{.15}}} \right){\text{K}}}}{{{\text{50 L}}}}\n&= 1.2321{\text{ atm}}\n&\approx 1.232{\text{ atm}}\n\end{aligned}$

The pressure is to be converted into mm Hg. The conversion factor for this is,

${\text{1 atm}} = {\text{760 mm Hg}}$

So the pressure of ideal gas can be calculated as follows:

$\begin{aligned}{\text{P}} &= \left({{\text{1}}{\text{.232 atm}}}\right)\left( {\frac{{{\text{760 mm Hg}}}}{{{\text{1 atm}}}}}\right)\n&= 936.3{\text{2 mm Hg}} \n&\approx 93{\text{6 mm Hg}}\n\end{aligned}$

Therefore the pressure of the ideal gas is 936 mm Hg.

3. The formula to calculate the mass percent of KBr is as follows:

${\text{Mass}}\;{\text{percent}}=\left( {\frac{{{\text{Mass of KBr}}}}{{{\text{Mass of solution}}}}}\right)\left( {100} \right)$ ......(4)

The mass of KBr is 12.4 g.

The mass of the solution is 170 g.

Substitute these values in equation (4).

$\begin{aligned}{\text{Mass}}\;{\text{percent}}&= \left( {\frac{{{\text{12}}{\text{.4 g}}}}{{{\text{170 g}}}}} \right)\left( {100} \right)\n&= 7.294\;\% \n&\approx 7.{\text{3 \% }}\n\end{aligned}$

Therefore the concentration of the solution is 7.3 %.

Learn more:

1. Which statement is true for Boyle’s law: brainly.com/question/1158880

2. Calculation of volume of gas: brainly.com/question/3636135

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Mole Concept

Keywords: P, V, n, R, T, ideal gas, pressure, volume, 17.6 L, 936 mm Hg, 7.3 %, 0.9 mol, 950 mm Hg, 50 L, 2.5 mol, 12.4 g, 170 g, KBr

What types of atoms form cations

Answers

Cations are formed when atoms lose electrons, resulting in a net positive charge.

Generally, cations are formed by atoms of metals. Metals tend to have relatively low ionization energies, allowing them to easily lose electrons and form positively charged cations. Examples of metals that commonly form cations include sodium (Na⁺), calcium (Ca²⁺), iron (Fe²⁺ or Fe³⁺), and aluminum (Al³⁺), among others. It is important to note that not all metals form cations, as some metals can exhibit variable oxidation states or form anions in certain compounds.

Hence, Cations are formed when atoms lose electrons.

Learn more about cations here:

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Answer:

positively charged atoms

Explanation:

If it takes 25 mL of 0.05 M HCl to neutralize 345 mL of NaOH solution, what is the concentration of the NaOH solution? (Round answer to 4 decimal places) *

Answers

Answer:

Concentration of NaOH= 0.0036 M

Explanation:

Given data:

Volume of HCl = 25 mL

Concentration of HCl = 0.05 M

Volume of NaOH = 345 mL

Concentration of NaOH = ?

Solution:

Formula:

C₁V₁ = C₂V₂

C₁ = Concentration of HCl

V₁ = Volume of HCl

C₂ = Concentration of NaOH

V₂ = Volume of NaOH

Now we will put the values in formula.

C₁V₁ = C₂V₂

0.05 M × 25 mL = C₂ × 345 mL

1.25 M.mL = C₂ × 345 mL

C₂ = 1.25 M.mL/345 mL

C₂ = 0.0036 M

Final answer:

To find the concentration of the NaOH solution, we can use the concept of titration. By using the equation Moles = Concentration * Volume, we can calculate the moles of HCl used and then use the ratio of moles between HCl and NaOH to find the concentration of the NaOH solution.

Explanation:

To find the concentration of the NaOH solution, we need to use the concept of titration. From the given information, it takes 25 mL of 0.05 M HCl to neutralize 345 mL of NaOH solution. We can use the equation Moles = Concentration * Volume to find the amount in moles of HCl used. Then, we can use this information to calculate the concentration of the NaOH solution.

First, let's calculate the moles of HCl used:

Moles of HCl = (0.05 M) x (0.025 L) = 0.00125 mol

Next, we can use the ratio of moles between HCl and NaOH, which is 1:1, to find the moles of NaOH in the solution:

Moles of NaOH = 0.00125 mol

Finally, we can calculate the concentration using the formula:

The concentration of NaOH = (0.00125 mol) / (0.345 L) = 0.00362 M

Learn more about Concentration of NaOH solution here:

brainly.com/question/34408783

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Is it possible to make CD without plastic? why or why not?

Answers

No, it is not possible to make CD by other material except plastic.

The full form of CD is compact disks. It is simple disk of plastic

Why CD made up of plastics ?

The CD is made up of plastic mainly with polycarbonate plastic (PC) .

The PC is stronger and mechanically more stable. CD must be stronger enough to resist any mechanical damage like scratching.
The PC are quite temperature and and impact resistance and highly transparent.
It provides the disc depth necessary to maintain laser focus on the metal and data layer.
The surface of the CD is reflective because it is coated with thin layer of aluminium and sometimes gold .

learn about Aluminium

brainly.com/question/14958942

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No, its not possible because mostly substances are not durable also u can take an example of iron. if we make a cd of iron then rusting occurs
hope it helps u

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