PLS HELP!!!
What does it mean when there is a physical change?


A new substance has been formed.


Matter has changed on the molecular level.


Matter has changed from one substance into another.


Matter has changed size, shape or form.

Answer: 16.21

Explanation:

A student measures the length of two pieces of paper as 8.21 in and 8.0 in. the total length is 16.21 with 4 significant figures.

The significant figures or digits are the form of scientific methd which represent the digit from zero to nine and use when the value is uncertain where starting zeros are not significant and decimal is also not a significant figure.

In the given value the total is 16.21 with 4 significant figures with it has 4 significant digits and the decimal with it is not significant after adding from which the respective value is here.

Therefore,  with 4 significant figures where the student measures the length of two pieces of paper as 8.21 in and 8.0 in. the total length is 16.21.

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Alcohol is both a Depressant and a Muscle Relaxer. Therefore the answer would be both!

Hope this helps :)

Answer:

-251.9°C

Explanation:

Given data:

Initial volume = 35.0 L

Initial pressure = 4.62 atm

Initial temperature = -10.0 °C (-10.0 +273 = 263.0 K)

Final temperature = ?

Final volume = 15.0 L

Final pressure = 8.71 atm

Solution:

According to general gas equation:

P₁V₁/T₁ = P₂V₂/T₂

Now we will put the values,

4.62 atm × 35.0 L / 263.0 K =  8.71 atm ×  15.0 L  /T₂

T₂  = 8.71 atm ×  15.0 L ×   263.0 K /  4.62 atm × 35.0 L

T₂  = 34360.95 atm.L.K /161.7 atm.L

T₂  = 21.26 K

Kelvin to °C:

21.26 - 273.15 K = -251.9°C

Answer:

Dissolves in water: Acetone, 1-propanol, Methanol

Do not dissolve in water: Hexane, Decane

Explanation:

From the principle that like dissolves like,polar substances will dissolve in polar solutions, while non-polar substances will dissolve in non-polar substances.

Water is a polar solution, therefore, polar substances will dissolve in it.From the given options:

Acetone is a polar molecule, therefore, it will dissolve in water.

1-propanol is a polar molecule, therefore, it will dissolve in water.

Hexane is a non-polar molecule, therefore, it will not dissolve in water.

Methanol is a polar molecule, therefore, it will dissolve in water.

Decane is a non-polar molecule, therefore, it will not dissolve in water

Answer:

CaHPO4 i think

Explanation:

Answer:

1.1 M

General Formulas and Concepts:

Explanation:

Step 1: Define variables

1.2 mol KCL

1.1 L of solution

M = unknown

Step 2: Solve for Molarity

Step 3: Check

We are given 2 sig figs. Follow sig fig rules.

1.09091 M ≈ 1.1 M

H₂ will have the highest average  kinetic energy

Energy because this motion is expressed as Kinetic energy (KE) which can be formulated as:  

[tex]\tt \displaystyle KE=\frac{1}{2}mv^2[/tex]

Average velocities of gases can be expressed as root-mean-square averages. (V rms)  

[tex]\large{\boxed{\bold{v_{rms}=\sqrt{\frac{3RT}{Mm} } }}[/tex]

R = gas constant, T = temperature, Mm = molar mass of the gas particles

From the two equations above, it can be concluded

So the highest KE is owned by the gas with the smallest molar mass

Molar mass of the gas :

A) H₂  : 2 g/mol

B) N₂ : 28 g/mol

C) O₂  : 32 g/mol

D) F₂ : 38 g/mol

So H₂ has the highest average  kinetic energy

At a constant temperature: E. All the gases will have the same average  kinetic energy.

According to the kinetic-molecular theory, the average kinetic energy of gas molecules (particles) is highly dependent on temperature.

Hence, the average kinetic energy of gas molecules (particles) is directly proportional to the absolute temperature of the gas.

At a constant temperature, all gases would have the same average kinetic energy according to the kinetic-molecular theory of gases.

In conclusion, all the gases would have the same average kinetic energy since the temperature is constant.

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Answer:

Number of moles = 0.94 mol

Explanation:

Given data:

Number of moles of sodium chloride = ?

Volume of sodium chloride = 1.25 L

Concentration of solution = 0.750 mol/L

Solution:

Formula:

Concentration = number of moles/ volume in L

By putting values.

0.750 mol/L = number of mole / 1.25 L

Number of moles =  0.750 mol/L×1.25 L

Number of moles = 0.94 mol

Answer: D

Explanation:

Hydropower

Answer:

5.00 moles O₂

General Formulas and Concepts:

Chemistry - Atomic Structure

Explanation:

Step 1: Define

3.01 × 10²⁴ molecules O₂

Step 2: Convert

[tex]3.01 \cdot 10^{24} \ mc \ O_2(\frac{1 \ mol \ O_2}{6.022 \cdot 10^{23} \ mc \ O_2} )[/tex] = 4.99834 moles O₂

Step 3: Check

We are given 3 sig figs. Follow sig fig rules and round.

4.99834 moles O₂ ≈ 5.00 moles O₂

Answer:

compound

Explanation:

Answer:

The answer is compound

Explanation:

Answer:

the answer is d. frequency

Answer:

[tex]T_f=26.7\°C[/tex]

Explanation:

Hello.

In this case, when two substances at different temperature are placed in contact in an isolated container, we can say that the heat lost by the hot substance is gained by the cold substance. In such a way, since granite is at 76.0 °C and water at 22.0 °C we infer granite is hot and water is cold, so we write:

[tex]Q_{granite}=-Q_{water}[/tex]

In terms of mass, specific heat and change in temperature, we write:

[tex]m_{granite}C_{granite}(T_f-T_{granite})=-m_{water}C_{water}(T_f-T_{water})[/tex]

Thus, since the temperature is the same for both substance, we can solve for it as shown below:

[tex]T_f=\frac{m_{granite}C_{granite}T_{granite}+m_{water}C_{water}T_{water}}{m_{granite}C_{granite}+m_{water}C_{water}}[/tex]

By plugging in each variable, we obtain:

[tex]T_f=\frac{11.1g*0.790\frac{J}{g\°C} *76.0\°C+22.0g*4.18\frac{J}{g\°C} *22.0\°C}{11.1g*0.790\frac{J}{g\°C} +22.0g*4.18\frac{J}{g\°C}}\\\\T_f=26.7\°C[/tex]

Best regards!

Answer:

3.64g

Explanation:

Given parameters:

Mass of NH₃  = 18.1g

Mass of Cu₂O  = 90.4g

Unknown:

Limiting reactant  = ?

Mass of N₂ formed  = ?

Solution:

The reaction equation is given as:

       Cu₂O + 2NH₃ → 6Cu + N₂ + 3H₂O

The limiting reactant is the one in short supply in the reaction. Let us find the number of moles of the given species;

  Number of moles = [tex]\frac{mass}{molar mass}[/tex]  

Molar mass of Cu₂O = 2(63.6) + 16  = 143.2g/mol

Molar mass of NH₃  = 14 + 3(1) = 17g/mol

Number of moles of Cu₂O = [tex]\frac{18.1}{143.2}[/tex]   = 0.13moles

Number of moles of NH₃   = [tex]\frac{90.4}{17}[/tex]   = 5.32moles

  From this reaction;

       1 mole of  Cu₂O combines with 2 mole of NH₃

So   0.13moles of  Cu₂O will combine with 0.13 x 2 mole of NH₃

                                              = 0.26moles of NH₃

Therefore, Cu₂O is the limiting reactant. Ammonia is in excess;

Mass of N₂;

   Mass = number of moles x molar mass

    1 mole of Cu₂O  will produce 1 mole of N₂

    0.13 mole of Cu₂O  will produce 0.13 mole of N₂

    Mass  = 0.13 x (2 x 14) = 3.64g

Answer:

The best and most correct answer among the choices provided by your question is the fourth choice.

The data explains that sodium atoms hardly ever form 2+ ions.

I hope my answer has come to your help. Thank you for posting your question here in Brainly. We hope to answer more of your questions and inquiries soon. Have a nice day ahead!

Explanation:

Answer:

iron i believe is ionic and carbon is covalent

Explanation:

if im wrong correct me

Answer:

Molar mass of NH4SO2=104gmol`

No of moles of NH4SO2=2.3g/104gmol`=0.022×(avagadro's constant)

Answer:

C

Explanation:

Grams 3/4

Answer:

9g

Explanation:

number of moles × the moleculars mass

Answer:

1.5 × 10² mL

Explanation:

Step 1: Given data

Step 2: Calculate the final volume of the gas

For an ideal gas, we can calculate the final volume of the gas using Boyle's law.

P₁ × V₁ = P₂ × V₂

V₂ = P₁ × V₁/P₂

V₂ = 1.9 atm × 80 mL/1.0 atm

V₂ = 1.5 × 10² mL

Since the pressure decreased, the volume of the gas increased.

Answer:

[tex]V_{base}=9.442mL[/tex]

Explanation:

Hello!

In this case, when acetic acid is titrated with sodium hydroxide, the following chemical reaction is carried out:

[tex]CH_3COOH+NaOH\rightarrow CH_3COONa+H_2O[/tex]

Whereas there is a 1:1 mole ratio between the acid and the base, which means that at the equivalence point we evidence:

[tex]n_{acid}=n_{base}[/tex]

Which in terms of volumes and concentrations is written as:

[tex]M_{acid}V_{acid}=M_{base}V_{base}[/tex]

Thus, solving for the required volume of base, we obtain:

[tex]V_{base}=\frac{M_{acid}V_{acid}}{M_{base}}=\frac{0.1894M*10.00mL}{0.2006M}\\\\ V_{base}=9.442mL[/tex]

Best regards!

Answer:

6.711 × 10²⁴ molecules Mg(OH)₂

General Formulas and Concepts:

Chemistry - Atomic Structure

Explanation:

Step 1: Define

650.0 g Mg(OH)₂

Step 2: Define conversions

Avogadro's Number

Molar Mass of Mg - 24.31 g/mol

Molar Mass of O - 16.00 g/mol

Molar Mass of H - 1.01 g/mol

Molar Mass of Mg(OH)₂ - 24.31 + 2(16.00) + 2(1.01) = 58.33 g/mol

Step 3: Convert

[tex]650.0 \ g \ Mg(OH)_2(\frac{1 \ mol \ Mg(OH)_2}{58.33 \ g \ Mg(OH)_2} )(\frac{6.022 \cdot 10^{23} \ molecules \ Mg(OH)_2}{1 \ mol \ Mg(OH)_2} )[/tex]

= 6.71061 × 10²⁴ molecules Mg(OH)₂

Step 4: Check

We are given 4 sig figs. Follow sig fig rules.

6.71061 × 10²⁴ molecules Mg(OH)₂ ≈ 6.711 × 10²⁴ molecules Mg(OH)₂

Answer:

Explanation:

The mass of the bicycle can be found by using the formula

[tex]m = \frac{p}{v} \\ [/tex]

p is the momentum

v is the velocity

From the question we have

[tex]m = \frac{25}{2.5} \\ [/tex]

We have the final answer as

Hope this helps you

Answer:

If an atom gains or loses an electron, it bacomes an ion. An atom that gains a negative electron, it becomes a negative ion. If it loses an electron it becomes a positive ion

Explanation:

A lithium atom has 3 protons and 3 electrons. It can lose one of its electrons, making it an ion. It now has more positive protons than electrons so it has an overall positive charge. Therefore it is a positive ion.

A fluorine atom will tend to gain, rather than lose, an electron. By gaining a negative electron, it has an overall negative charge. It has become a negative ion.

Percent by mass : 4.10⁺³%

The concentration of a solution can be expressed in units such as molarity, normality, mass percent, volume percent etc.

[tex]\tt \%mass=\dfrac{mass~solute}{mass~solution}\times 100\%[/tex]

mass solute= mass of NaOH  

mass of NaOH :

[tex]\tt 0.001~mol/L\times 1~L\times 40~g/mol=0.04~g[/tex]

mass solution = 1000 g

% mass :

[tex]\tt \dfrac{0.04}{1000}\times 100=4.10^{-3}\%[/tex]

The percent by mass concentration of NaOH in the given solution is approximately 0.004%.

To calculate the percent by mass concentration of NaOH, we must find the mass of NaOH in solution.

First, we determine how many moles of NaOH are present in the solution:

Molarity (M) is calculated as moles of solute per liter of solution.

1 L = 0.001 M = mole of NaOH

We rearrange the equation to find that one mole of NaOH is equal to 0.001 moles.

Mass of NaOH = moles of NaOH * molar mass of NaOH

Mass of NaOH = 0.001 mol * 40.00 g/mol

Mass of NaOH = 0.04 g

The mass of the solution is 1000 g which is given in the question.

Percent by mass concentration of NaOH = (mass of NaOH / mass of solution) * 100%

Percent by mass concentration of NaOH = (0.04 g / 1000 g) * 100%

Percent by mass concentration of NaOH = 0.004%

Hence, the percent by mass concentration of NaOH in the given solution is approximately 0.004%.

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Answer:

This question is incomplete

Explanation:

This question is incomplete but the answer to the question can be correctly predicted from the available information from the question.

1. If a "container" (in this case a crucible) is closed throughout a heating experiment. Then it must be noted that water vapor will not be able to escape during the course of the experiment. The water vapor will form a "cloud" of water droplets under the cover of the crucible. And when this crucible is cooled, this water droplets return back to the content/substance inside the crucible.

2. When compared with the initial amount of water present in the substance in the crucible, the percentage of water "left" in the hydrate or substance in the crucible would be high. This is because the water vapor that was suppose to leave the crucible did not leave because the crucible was closed (thus causing very low amount of water vapour to leave).

Because of the student error, the percent water of crystallization value the hydrate will be lower than its actual value.

Evaporation is the process by which a liquid changes spontaneously to vapor.

In the experiment to determine percentage water of crystallization, the crucible is left open to ensure all the water molecules are removed by evaporation.

However,, since the student did not remove the crucible cover during heating, some water molecules will not be able to escape completely, but will return back to the salt.

Hence, the percent water of crystallization value the hydrate will be lower because the of mass of the anhydrous salt will be higher than its actual value.

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Answer: C

Explanation:

No matter the location on Earth, the sun always rises in the east due to its rotation pattern.

Answer:

Explanation:

in a combustion of ethane 2 moles of ethane react with 7 moles of O2

now no of moles in 54 gram of O2=mass/ molar mass

moles =54/32=1.7 moles

if 7 moles of O2 required 2 moles of ethane then 1.7 mole required=?

7 moles of O2=2 moles of C2H6

1.7 moles of O2=1.7*2/7=0.5 moles of C2H6

0.5 moles of C2H6 contain how much grams=?

mass= moles*molar mass=0.5*30=15

C : 52.2%, H : 13.1%, O:34.7%

The empirical formula is the smallest comparison of atoms of compound forming elements.  

A molecular formula is a formula that shows the number of atomic elements that make up a compound.  

(empirical formula) n = molecular formula  

11.5 g of Ethanol-C₂H₅OH contains 6.00 g of Carbon and 1.51 g of Hydrogen.

mass of Oxygen :

[tex]\tt 11.5-(6+1.51)=4~g[/tex]

Percent composition :

[tex]\tt \dfrac{6}{11.5}\times 100\%=52.2\%[/tex]

[tex]\tt \dfrac{1.51}{11.5}\times 100\%=13.1\%[/tex]

[tex]\tt \dfrac{4}{11.5}\times 100\5=34.7\%[/tex]