Which of the following is a common sign that a chemical change has occurred?

Answer:

For number 5 it is the 2nd one some stants has a mass of 1.25 g And the 2nd 1 number 6It is the 1st 1A subject has a melting point of 40

Answer:

the answer is {organisms}

Answer:

organisms

Explanation: I took the test

yes they can be changed becasue they are expose to the environment

That's why it's improtant to have a calorimeter so the energy and heat are contained

The total energy of an open system be changed if:

According to the First Law of Thermodynamics, energy cannot be created or destroyed, it can only change form.

An open system is a system that has an interaction with its environment where matter or energy can be added or removed from the environment.

As a result of this, the total energy of an open system can be changed if there is an exchange between matter and energy and they remain constant.

Therefore, the correct answer is an exchange has to take place for the total energy in an open system to be changed.

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Answer:

1.55×10²² molecules.

Explanation:

We'll begin by calculating the number of mole in 5.32 g of pure lead (Pb). This can be obtained as follow:

Mass of Pb = 5.32 g

Molar mass of Pb = 207 g/mol

Mole of Pb =?

Mole = mass /molar mass

Mole of Pb = 5.32/207

Mole of Pb = 0.0257 mole

Finally, we shall determine the number of molecules in 0.0257 mole of Pb. This can be obtained as follow:

From Avogadro's hypothesis,

I mole of Pb contains 6.02×10²³ molecules.

Therefore, 0.0257 mole will contain = 0.0257 × 6.02×10²³ = 1.55×10²² molecules.

Therefore, 5.32 g of pure lead (Pb) contains 1.55×10²² molecules.

Answer:

A) oxygen moles/sec = 48 * 10 ^-14  mol/sec

B) mass of oxygen = 1536*10^-14 grams

Explanation:

cross sectional area of cylinder = 2cm^2 = 2 * 10^-4 m^2

length of cylinder = 5 cm = 0.05 m

concentration at one end = 0.2 mol m^-3

concentration falls linearly at other end = 0.05 mol m^-3

Diffusion constant of oxygen = 8 * 10^-10  m^2 s^-1

A ) Number of moles of oxygen passing every second

 N = A * D * [tex]\frac{dc}{dt}[/tex]   ------- ( 1 )

A = area , D = diffusion constant,  [tex]\frac{dc}{dt}[/tex] = rate of change of diffusion

dc /dt = ( 0.2 - 0.05 ) / 0.05  = 3 mol m^-4

back to the equation

N = ( 2 * 10^-4 ) * ( 8 * 10^-10 ) * ( 3 ) = 48 * 10 ^-14  mol/sec

B) Mass of oxygen passing down the cylinder each second

This can be obtained by converting : 48 * 10^-14 moles to grams

1 mole of oxygen  =  32 grams of oxygen

therefore : 48 * 10^-14 moles of oxygen = ( 32 * (48*10^-14) = 1536*10^-14 grams

Answer:

im pretty sure the answer is b

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Answer:

2. Worm Y reproduces sexually, which gives it genetic variation.

Answer:

B      Worm Y reproduces sexually, which gives it genetic variation.

Explanation:

hope you all have a good day

Answer:

A

Explanation:

the number of molecule won't be twice as fructose has 12 hydrogen molecules and lactose has 22 hydrogen molecules

From the given statements, the statement saying that the number of atoms in Lactose is twice the number of atoms in Fructose is not correct. Thus option A is correct.

The given molecules in the list are Glutamine, Lactose, fructose, and Sorbitol.

The number of atoms in the following compounds is:

Statement A says that the number of atoms in Lactose is twice the number of atoms in Fructose. The twice atoms of Fructose are 48 atoms. The number of atoms of lactose is 45.

Thus statement A is incorrect. Thus option A is correct.

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Answer:

The total amount of heat is 250.64 kcal.

Explanation:

Given that,

Total amount of heat = 2.000 kg

Temperature of snow = -15.00°C

Temperature of water = 38.00°C

Heat of fusion of water = 1.44 kcal/mol

Specific heat of solid water = 0.488 cal/g°C

Specific heat of liquid = 1.00 cal/g°C

We need to calculate the heat required to bring temperature -15°C to 0°C snow

Using formula of heat

[tex]Q_{1}=mc_{p}\Delta T[/tex]

Put the value into the formula

[tex]Q_{1}=2000\times0.488\times(0+15)[/tex]

[tex]Q_{1}=14640\ cal[/tex]

[tex]Q_{1}=14.640\ kcal[/tex]

We need to calculate the heat required to convert 0°C snow  into 0°C water

Using formula of heat

[tex]Q_{2}=ml[/tex]

Put the value into the formula

[tex]Q_{2}=\dfrac{2000}{18}\times1.44[/tex]

[tex]Q_{2}=160\ kcal[/tex]

We need to calculate  heat required to increases temperature of water from 0°C  to 38°C

Using formula of heat

[tex]Q_{3}=mc_{p}\Delta T[/tex]

Put the value into the formula

[tex]Q_{3}=2000\times1.00\times(38-0)[/tex]

[tex]Q_{3}=76000\ cal[/tex]

[tex]Q_{3}=76\ kcal[/tex]

We need to calculate the total heat

Using all heat amount

[tex]Q=Q_{1}+Q_{2}+Q_{3}[/tex]

Put the value into the formula

[tex]Q=14.640+160+76[/tex]

[tex]Q=250.64\ kcal[/tex]

Hence, The total amount of heat is 250.64 kcal.

Answer:

It's probably C

The forces between liquid particles are weaker than the forces between solid particles. This means that liquid particles are further apart and can move about more easily. Since the particles can move, the liquid can flow and take the shape of its container

Sorry if the answer is wrong!!!!!!

Answer:

the answer is HYPOTHESIS your welcome

Explanation:

Answer:

i cry when im alone

Explanation:

Answer:

b-ovaries

Explanation:

Answer:

ovaries

Explanation:

i just know trust me tell me if its wrong

Answer:

its shorter than a regular one

Explanation:

the only reason is simply because it is shorter

Answer:

it's A. if the force of gravity is greater than the buoyant force, the object will sink.

Explanation:

just took the quiz on a p e x

Answer:

No reaction should occur

Explanation:

Water cannnot be made from the components

Nothing will be released as a gas

Both products are soluible in water therefore will not form a precipitate.

If I mix a solution of Na2SO4 and KCl, no reaction should occur.

Whether or not, a reaction occurs when two substances are mixed depends on the respective positions of the substances in the electrochemical series.

Now, we are expecting the reaction; Na2SO4 (aq) + 2 KCl(aq) + 2 NaCl(aq) + K2SO4 (aq) to occur. The big question is, between sodium and potassium, which is higher in the electrochemical series?

A little look into the image attached shows that potassium is higher than sodium in the series so the reaction is possible.

However, the both products are aqueous, they are both soluble in water hence no visible reaction occurs.

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Answer:

CO2

Explanation:

the subscript tells you how many of one element is used for this case there is one black atom and 2 red ones so you only need 1 carbon and 2 oxygens.

hope this helps. brainliest please?

Answer:

Explanation:

To find the concentration of new solution we use the formula

[tex]C_1V_1 = C_2V_2[/tex]

where

C1 is the concentration of the stock solution

V1 is the volume is the volume of the stock solution

C_2 is the concentration of the diluted solution

V2 is the volume of the diluted solution

Since we are finding the the concentration of new solution

[tex]C_2 = \frac{C_1V_1}{V_2} \\[/tex]

From the question

C1 = 0.575 M

V1 = 298 mL

V2 = 750 mL

We have

[tex]C_2 = \frac{0.575 \times 298}{750} \\ = 0.228466666...[/tex]

We have the final answer as

Hope this helps you

The answer would be B.

Answer:

2.08g

Explanation:

Given parameters:

  Volume of CuSO₄  = 3.29mL

  Molarity  = 4M

Unknown:

Mass of CuSO₄ = ?

Solution:

Let us find the number of moles from the given parameters first;

     Number of moles  = molarity x volume

           1000mL = 1L

Express the volume of the given CuSO₄ in L = 3.29 x 10⁻³L

   Number of moles  = 4 x 3.29 x 10⁻³ = 0.013mol

So;

  Mass of CuSO₄ = number of moles x molar mass

      Molar mass of  CuSO₄  = 63.6 + 32 + 4(16) = 159.6g/mol

 Mass of CuSO₄  = 0.013mol  x 159.6g/mol

 Mass of CuSO₄  = 2.08g

Answer:

Explanation:

You will need to look up the Standard Heats of Formation* for each substance and apply Hess's Law Equation.

ΔH⁰(rxn) = ∑ΔH⁰(Products) - ∑ΔH⁰(Reactants)

*Std Heats of Formation can be found in the appendix of most college chem texts.

For this problem:

Given               CaCO₃(s)       =>           CaO(s)        +      CO₂(g)

∑ΔH⁰:          -635.1 Kj/mole            -393.5Kj/mole         -1206.9

ΔH⁰(rxn) = [(-393.5 Kj/mole) + (-393.5Kj/mole)] - (-1206.9Kj/mole)

= (-635.1 -393.5 + 1206.9) Kj/mole

= +178.3 Kj/mole

Answer:

656.3 kJ

This reaction is endothermic

Explanation:

edge 2020

Answer:

0.219 g/mL.

Explanation:

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

Mass = 25 g

Volume = 114 mL

Density =.....?

Density of a substance is simply defined as the mass of the substance per unit volume of the substance. Mathematically, it is expressed as:

Density = mass /volume

With the above formula, we can obtain the density of the substance given in the question above as follow:

Mass = 25 g

Volume = 114 mL

Density =.....?

Density = mass /volume

Density = 25/114

Density = 0.219 g/mL

Therefore, the density of the substance is 0.219 g/mL

Answer:

Mass = 2.8 g

Explanation:

Given data:

Number of molecules of CO = 6.2×10²²

Mass of CO = ?

Solution:

We will use Avogadro number.

It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance.

The number 6.022 × 10²³ is called Avogadro number.

For example,

18 g of water = 1 mole = 6.022 × 10²³ molecules of water

For given  6.2×10²² molecules of CO mass will be,

1 mole = 6.022 × 10²³ molecules of CO

6.2×10²² molecule × 1 mole/  6.022 × 10²³ molecules of CO

0.1 mol

Mass of CO:

Mass = number of moles  × molar mass

Mass = 0.1 mol  × 28 g/mol

Mass = 2.8 g

Answer:

Explanation:

The density of a substance can be found by using the formula

[tex]density = \frac{mass}{volume} \\[/tex]

From the question

mass = 8.11 g

volume = final volume of water - initial volume of water

volume = 44.72 - 25.26 = 19.46 mL

We have

[tex]density = \frac{8.11}{19.46} \\ = 0.416752312...[/tex]

We have the final answer as

Hope this helps you

Answer:

During the process of reaching thermal equilibrium heat is transferred between the object. heat is always transferred from the object at the higher temperature to the object with lower temperature. For a gas, the heat transfer is related to a change in temperature.

Answer:

Copper Atoms

Explanation:

All copper atoms have atomic number 29: all their nuclei contain 29 protons. But they also contain uncharged particles called neutrons. In natural copper, the atoms are of two kinds. One has 29 protons and 34 neutrons in the nucleus; the other has 29 protons and 36 neutrons