1 poin
12. Which scientist said that electrons exist in discrete energy levels?
A. Thomson
B. Rutherford
C. Bohr
D. Dalton

Answer:

Burning gasoline in a lawnmower is a chemical change.

Explanation:

Here, a combustion reaction takes place. Freezing water to make ice cubes, melting gold to make jewellery and boiling water for soup are examples of physical change since, only a change in physical state takes place.

Answer:

59.4%

Explanation:

CuSO4(aq) + 2NaOH(aq) -----> Cu(OH)2(aq) + Na2SO4 (aq)

Ratio of molesCuSO4 to NaOH is 1:2

To determine the limiting reagent;

For CuSO4

Number of moles= 638.44g/160 = 4 moles

1 mole of CuSO4 yields 1 mole of Cu(OH)2

4 moles of CuSO4 also yields 4 moles of Cu(OH)2

For NaOH

Number of moles= 240g/40g/mol= 6 moles

2 moles of NaOH yields 1 mole of Cu(OH)2

6 moles of NaOH yields 6× 1/2 = 3 moles of Cu(OH)2

Hence NaOH is the limiting reactant.

Hence mass of Cu(OH)2 = 3 × 98 g/mol

= 294 g

% yield = actual yield/ theoretical yield × 100

% yield= 174.6 /294 × 100/1

% yield = 59.4%

The percent yield is   59.4%

Firstly write the balanced chemical equation:

CuSO₄(aq) + 2NaOH(aq) → Cu(OH)₂(aq) + Na₂SO₄ (aq)

Ratio of moles for CuSO₄ to NaOH is 1:2

To determine the limiting reagent:

For CuSO₄:

[tex]\text{Number of moles}= \frac{ 638.44g}{160}= 4 \text{moles}[/tex]

1 mole of CuSO₄ produces 1 mole of Cu(OH)₂

4 moles of CuSO₄ will produce 4 moles of Cu(OH)₂

For NaOH:

[tex]\text{Number of moles}= \frac{240g}{40g/mol} = 6 \text{moles}[/tex]

2 moles of NaOH yields 1 mole of Cu(OH)₂

6 moles of NaOH yields [tex]6*\frac{1}{2} = 3[/tex] moles of Cu(OH)₂

Hence, NaOH is the limiting reactant.

Therefore, mass of Cu(OH)₂ = [tex]3 * 98 g/mol= 294 g[/tex]

% yield = actual yield/ theoretical yield × 100

% yield= [tex]\frac{174.6}{294}* 100[/tex]

% yield = 59.4%

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Answer:

c

Explanation:

got it right on test

Oxygen will appear in the final equation as O2 reactant.

A chemical equations shows the interplay between reactants and products. The reactants are on the left hand side while the products are at the right  hand side.

Looking at the two equations, we know that oxygen will appear in the final equation as O2 reactant.

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Answer:

I believe its false

Explanation:

a carrying capacity is the maximum amount of living things that can be held in a single container

Answer:

Populations vary in their capacity to grow. The maximum rate at which a population can increase when resources are unlimited and environmental conditions are ideal is termed the population's biotic potential. Each species will have a different biotic potential due to variations in

the species' reproductive span (how long an individual is capable of reproducing)

the frequency of reproduction (how often an individual can reproduce)

"litter size" (how many offspring are born each time)

survival rate (how many offspring survive to reproductive age)

There are always limits to population growth in nature. Populations cannot grow exponentially indefinitely. Exploding populations always reach a size limit imposed by the shortage of one or more factors such as water, space, and nutrients or by adverse conditions such as disease, drought and temperature extremes. The factors which act jointly to limit a population's growth are termed the environmental resistance. The interplay of biotic potential and density-dependent environmental resistance keeps a population in balance.

Answer:

Plants need chloroplasts to capture light energy.

Plant cells use light energy to make food.

The cell uses the energy from food.

Hope it helps ;)

Answer:

The equipments you should have ready to start the crucible experiment includes: safety goggles, crucible with lid, crucible tong, ring support with clay triangle, Bunsen burner and heat resistant tile.

Explanation:

Crucible is an equipment in the laboratory which is suitable for heating a sample to extreme heat over a flame, Modern laboratory crucible are made up of graphite- based composite materials for achievement of higher performance. Because extreme heat is involved, you should locate the correct labware for the experiment, including the equipment to safely handle and support the crucible. These equipments includes:

--> Safety goggles: Because you will work with chemical it is advisable to use a safety goggles which protects the eyes from dangerous floating chemical aerosol.

--> crucible with lid: This is the main apparatus with the lid (cover) which is used to cover the crucible to prevent spilling of the boiling chemical.

--> Crucible tong: These are scissors like tools used to grasp hot crucible.

--> Ring support with clay triangle: the clay triangle is used to hold crucible when they are being heated. They usually sit on a ring stand.

--> Bunsen burner: Produces a single open gas flame which can be used for heating.

With the safety equipments listed above, you can carry out experiment using the crucible. These equipments helps minimise laboratory hazard that may occur should Incase it's not available.

Safety goggles, crucible with lid, crucible tong, ring support with clay triangle, Bunsen burner and heat resistant tiles equipment should be ready to start the crucible experiment.

Crucible is having a cup like structure and formed by the mixture of graphite and porcelain, and these two are having very high melting or boiling point; that's why crucible is used to heat any sample at high temperature.

Before doing any experiment with crucible you have to carry:

Equipment we should ready to start crucible experiment are safety goggles, crucible with lid, crucible tong, ring support with clay triangle, Bunsen burner and heat resistant tiles.

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Answer:

t = 37.1 s

Explanation:

The equation for the reaction is given as;

                  2 N2O5(g)  --> 4 NO2 + O2

Initial:          0.110                  -             -

change:        -2x                  +4x        +x

Final:          0.110 - 2x           +4x        +x

But final = 0.150atm;

0.110 - 2x    +  4x   +  x = 0.150 atm

3x = 0.150 - 0.110

x = 0.0133 atm

Pressure in reactant side;

0.110 - 2x

0.110 - 2 (0.0133) = 0.0834 atm

The integral rate law expression is given as;

ln ( [A] / [Ao] ) = -kt

k =  rate constant = 7.48*10^-3*s-1

ln (0.0834/0.11) = (7.48*10^-3)  t

upon solving, t = 37.1 s

In this exercise we have to use the knowledge of chemistry to calculate the necessary time that the pressure can hold the system, in this way we can say that this time corresponds to:

[tex]t = 37.1 s[/tex]

First we have to use the reaction equation given as:

[tex]2 N_2O_5(g) \rightarrow 4 NO_2 + O_2[/tex]

This equation can be rewritten in terms of pressure, so it will be;              

[tex]0.110 - 2X + 4X + X = 0.150 atm\\3X = 0.150 - 0.110\\X = 0.0133 atm[/tex]

Pressure in reactant side, will be:

[tex]0.110 - 2X \rightarrow 0.110 - 2 (0.0133) = 0.0834 atm[/tex]

The integral rate law expression is given as, knowing that the rate constant is  [tex]7.48*10^{-3}*s^{-1}[/tex]

[tex]\int\limits^{0.0834}_{0.11} {(7.48*10^{-3}) t} \, dt = t = 37.1 s[/tex]

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Answer:The five major types of species interactions, summarized in Figure 10, are competition, predation, parasitism, mutualism, and commensalism.

Explanation:

Answer:

See explanation

Explanation:

a)  The average kinetic energy of the molecules of a gas depends on the temperature and the molar mass of the gas. However, at the same temperature, all gases have the same average kinetic energy. Hence Xe and Ne atoms have the same average kinetic energy.

b) To decrease the kinetic energy of Xe atoms the temperature must be changed. When the temperature is changed, Xe a lower average kinetic energy due to its larger molar mass.

c) All gases occupying the same volume have equal number of particles at the same temperature and pressure according to Avogadro's law. Therefore, since Xe and Ne occupy the same volume at the same temperature but different pressures they do not contain the same number of particles. Xe gas contains more particles because there are more moles of Xe gas present than moles of Ne gas. The greater the number of moles of gas present, the more the number of gas particles present.

Answer:

Almost all corn oil is expeller-pressed

Explanation:

then solvent-extracted using hexane or 2-methylpentane (isohexane). The solvent is evaporated from the corn oil, recovered, and re-used. After extraction, the corn oil is then refined by degumming and/or alkali treatment, both of which remove phosphatides.Oct 16, 2020

Answer:

Sum of their partial pressures

Explanation:

If two gases are present in a container, the total pressure in the container is equal to the sum of their partial pressures.

This solution is based on the Dalton's Law of Partial Pressures.

Dalton's Law of Partial Pressure states that "the total pressure of a mixture of gases is equal to the sum of the partial pressures of the constituent gases".

A partial pressure is the pressure a gas would exert if it alone occupied the volume of the gas mixture.

Answer:

See explanation

Explanation:

In an atom, the inner electrons may shield the outer electrons from the attractive force of the nucleus. We, refer to this phenomenon as the shielding effect, It is defined as a decrease in the magnitude of attraction between an electron and the nucleus of an atom having more than one electron shell (energy level).

Shielding effect increases down the group due to addition of more shells but decreases across the period due to the increase in the size of the nuclear charge.

As the magnitude of shielding increases down the group, ionization of electrons becomes easier and the first ionization energies of elements decreases as we move down the group. Since shielding effect decreases across the period, the first ionization energies of elements increases across the period.

Answer:

d = 43.5 g/cm³

Explanation:

Given data:

Mass of magnesium cube = 217.501 g

Volume of magnesium cube = 5.00 cm³

Density of magnesium cube = ?

Solution:

Formula:

d = m/v

d = density

m = mass

v = volume

by putting values,

d = 217.501 g/ 5.00 cm³

d = 43.5 g/cm³

Answer: The partial pressure of Argon , Neon and krypton are 48 kPa , 24 kPa and 8 kPa respectively.

Explanation:

According to Raoult's Law , the partial pressure of each component in the solution is equal to the total pressure multiplied by its mole fraction. It is mathematically expressed as

[tex]p_A=x_A\times P_{total}[/tex]

where, [tex]p_A[/tex] = partial pressure of component A

[tex]x_A[/tex] = mole fraction of A

[tex]P_{total}[/tex] = total pressure

mole fraction of Ar = [tex]\frac{\text {Moles of Ar}}{\text {total moles}}=\frac{60.0}{60.0+30.0+10.0}=0.6[/tex]

[tex]p_{Ar}=0.60\times 80.0kPa=48kPa[/tex]

mole fraction of Ne = [tex]\frac{\text {Moles of Ne}}{\text {total moles}}=\frac{30.0}{60.0+30.0+10.0}=0.30[/tex]

[tex]p_{Ne}=0.30\times 80.0kPa=24kPa[/tex]

mole fraction of Kr = [tex]\frac{\text {Moles of Kr}}{\text {total moles}}=\frac{10.0}{60.0+30.0+10.0}=0.10[/tex]

[tex]p_{Kr}=0.10\times 80.0kPa=8kPa[/tex]

Aluminum and Sulfur react to produce Aluminum sulfide(Al₂S₃)

Given

The reaction of Aluminium and Sulfur

Required

The products of the reaction

Solution

There are several types of reactions that can occur

Synthesis/combination reaction : 2 elements combine to form a single product

The general formula :

A + B ⇒ AB

For reaction above :

2Al + 3S ⇒ Al₂S₃

Answer: For the balanced redox equation, you should add the half reactions.

Like this.

Explanation:

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Answer:

that the poem needs to be finished heh pog

Explanation:

Answer:

Where is the poem?

Explanation:

Answer:

I think its b or c

Explanation:

hope this helps I mainly think b

Answer:

Explanation:

Answer:

A

Explanation:

Answer:

Explanation:

HCl    ⇄    H⁺    +   Cl⁻

HCl is a strong electrolyte so it will ionize completely .

moles of Cl⁻ in 100 mL of .1 HCl = .1 x .1 = .01 gram - ion .

CaCl₂ = Ca⁺² + 2 Cl⁻

1 mole                2 mole

moles of CaCl₂ in 200 mL of .1 M CaCl₂ = .2 x .1 = .02 gram mole  .

.02 gram mole of CaCl₂ will give 2 x .02 = .04 gram-ion of Cl⁻ ion .

Total gram - ion of Cl⁻ = .01 + .04 = .05 gram-ion .

Total volume = 300mL = .3 L

molarity of Cl⁻ = .05 / .3 = .167 M .

HCl    ⇄    H⁺    +   Cl⁻

moles of H⁺ = moles of Cl⁻ = .01 gram-ion .

volume of solution = .3 L

molarity of H⁺ = .01 / .3 = 33.33 x 10⁻³ M .

[ H⁺] [ OH⁻] = 10⁻¹⁴

33.33 x 10⁻³  [ OH⁻] = 10⁻¹⁴

[ OH⁻] = 3 x 10⁻¹³

pOH = - log[OH⁻] = - log3 x 10⁻¹³

13-log3

= 13 - .477

12.52

or ,

pH = - log[H⁺] = - log33.33 x 10⁻³

3 - log 33.33

= 3 - 1.52

= 1.48

pOH = 14 - 1.48 = 12.52

Answer:

1:3

Explanation:

nitrogen and hydrogen combine qt high pressure and temperature to form ammonia gas.this method is used to prepare ammonia industrially and the process is called haber's process.

the balanced equation is given as:

N2+3H2=>2NH3

we can see that 1 mole of nitrogen combines with 3 moles of hydrogen to produce 2 moles of ammonia.

hence ratio of nitrogen and hydrogen molecules should be 1:3 for reactants to get used up completely.

I hope it's helpful!

Answer:

No, a mole of oxygen is about 16 grams

Explanation:

Answer:what is nacho3???

Explanation:

Answer:

Neptunium, Protactinium, plutonium and more

Explanation:

Answer:

11

Explanation:

Moles of KOH = [tex]10^{-2}[/tex]

Volume of water = 10 liters

Concentration of KOH is given by

[tex][KOH]=\dfrac{10^{-2}}{10}\\\Rightarrow [KOH]=10^{-3}\ \text{M}[/tex]

[tex][KOH][/tex] is strong base so we have the following relation

[tex][KOH]=[OH^{-}]=10^{-3}\ \text{M}[/tex]

[tex]pOH=-\log [OH^{-}]=-\log10^{-3}[/tex]

[tex]\Rightarrow pH=14-3=11[/tex]

So, pH of the solution is 11

Answer:

Explanation:

1) Given data:

Number of moles of lead = 4.3×10⁻³ mol

Mass of lead = ?

Solution:

Mass = number of moles × molar mass

Molar mass of lead = 207.2 g/mol

Mass = 4.3×10⁻³ mol × 207.2 g/mol

Mass =  890.96 g

2) Given data:

Number of atoms of antimony = 3.8×10²² atoms

Mass of antimony = ?

Solution:

1 mole contain 6.022 ×10²³ atoms

3.8×10²² atoms × 1 mol / 6.022 ×10²³ atoms

0.63×10⁻¹ mol

0.063 mol

Mass = number of moles × molar mass

Molar mass of lead = 121.76 g/mol

Mass = 0.063 mol ×  121.76 g/mol

Mass =  7.67 g

3) Given data:

Mass of tungsten = 15.5 Kg (15.5 kg × 1000 g/ 1kg = 15500 g)

Number of atoms = ?

Solution:

Number of moles of tungsten:

Number of moles = mass/molar mass

Number of moles = 15500 g / 183.84 g/mol

Number of moles = 84.3 mol

1 mole contain 6.022 ×10²³ atoms

84.3 mol  × 6.022 ×10²³ atoms / 1mol

507.65 ×10²³ atoms

Given :

Mass of Ba(OH)₂ , m = 35.5 g.

Volume of mixture, V = 325 mL = 0.325 L.

To Find :

The molarity of a solution.

Solution :

We know, molarity of a solution is given by :

[tex]M = \dfrac{Given \ Weight}{Molecular\ Mass\times Volume( L ) }[/tex]

We know, molecular mass of Ba(OH)₂ is given by :

M.M. = 171 g/mol

Putting all these values in given equation, we get :

[tex]M = \dfrac{35.5}{171\times 0.325}\ M\\\\M = 0.64\ M[/tex]

Hence, this is the required solution.

Answer:

a

Explanation:

it is an electrolyte because of its strong polar chemical bond