There are four sketches below. The first sketch shows a sample of Substance X. The three sketches underneath it show three different changes to the sample.
You must decide whether each of these changes is possible. If a change is possible, you must also decide whether it is a physical change or a chemical change.
Each sketch is drawn as if the sample were under a microscope so powerful that individual atoms could be seen. Also, you should assume that you can see the
entire sample, and that the sample is in a sealed box, so that no matter can enter or leave.
Sample of Substance X
oli
Change 1
Change 2
Change 3
Change 1 is:
Impossible
a physical change
Change 2 is:
Impossible
a physical change
Change 3 is
Impossible
a physical change
Explanation
Check

Explanation:

The % w/v s the number of grams of solute in 100 mL of solution

So it relates grams of solute with mL of solution.

Answer: B. grams and milliliters

Based on the mole ratio from the chemical reaction 3 moles of Br2 produces 2 moles of AlBr3. We can set this equation up to determine the unknown:

3.3 moles of Br2 is needed to reacts with 5 mol of AlBr3.

Atom A and B both have 10 protons A have 10 B has 11 neutrons is A and B are isotopes of same element.

Isotopes are the atoms of same elements , that has same number of proton but different number of neutrons , mass no. is depends on neutrons present in an atom. the given situation is :

                  number of proton      number of neutron

Atom A                10                               10

Atom  B                10                               11

Isotopes are the members of the same family of same elements.

Thus, Atom A and B both have 10 protons A have 10 B has 11 neutrons is A and B are isotopes of same element.

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We must first determine the heat needed to heat 175mL of water. In the working temperature range we can assume that the density of water is 1g/mL, so the mass of water that we must heat will be 175g of water.

Now, the heat we need to heat that mass of water is calculated with the following equation:

Where Q is the heat required to heat the water

Cp is the specific heat of water equal to 4186 J/g°C

delta T is the change of temperature = 25°C-20°C=5°C

We replace the know values:

Now, to heat the water they tell us that the glucose combustion will take place. We must assume that all the heat generated in the reaction will go to heating the water and that there is no heat loss to the environment.

The combustion reaction of glucose generates 2538.7 kJ/mol. So the moles of glucose needed will be:

We calculate the grams of glucose by multiplying the moles by the molar mass of glucose equal to 180.2g/mol

grams of glucose= 1.44 mol x 180.2 g/mol=260g

Answer: To heat 175 mL of water from 20.0 °C to 25.0°C are required 260g of glucose

To solve this question, we need to know the molar mass of Ca. It is 40 g/mol

There are 3 atoms of Ca in Ca3(PO4)2

So the mass of Ca in Ca3(PO4)2 is 3x40 = 120 g

So:

375 grams ---- 100%

120 g --- x

x = 32%

Answer: 32% of calcium.

The equation is balanced since the number of atoms of each element is the same on each side of the reaction.

Now, we will calculate the number of moles present in 10 grams of CaCO3. We will use the molar mass of CaCO3 for this

Assuming that the rest of the reactants are in excess, 0.1 mol of CaCO3 will react and form 0.1 mol of CO2, since the ratio is 1 to 1.

Now to calculate the volume, we can apply the ideal gas law which tells us:

Where,

P is the pressure (STP) =1 atm

V is the volume in Liters

n is the number of moles = 0.1 mol CO2

R is a constant = 0.08206 (atm L)/(mol K)

T is the temperature (STP)= 273.15K

Now, we clear the volume and write the known values:

The volume of CO2(at STP) produced would be 2.2L

The free energy of formation of the MgO is −597 kJ/mol.

We know that the free energy of formation is defined as the energy that is evolved or absorbed when a substance is formed from its components under standard conditions. In this case, we have that the magnesium and the oxygen are all pure substances.

It is important that we recall that the free energy of formation of a pure substance is zero. We have the free energy  of formation of the magnesium oxide as−597 kJ/mol.

Hence;

Sum of free energy of formation of products - Sum of free energy  of formation of reactants

We have;

(−597 kJ/mol) - (0  kJ/mol)

free energy of formation = −597 kJ/mol

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1) First, let's rewrite the equation:

3 H2 + N2 ---> 2 NH3

If you need to make 467 L ammonia gas (NH3), let's find out how many moles of it do we need.

For this, we use the molar volume of gases: 22.4L/mol

So:

467 L ------ x mol

22.4 L ----- 1 mol

22.4x = 467

x = 20.8 mol of NH3

2) Now we use the proportion of the chemical equation to find out the quantity in moles of N2 (nitrogen gas):

1 mol of N2 ---- 2 mol of NH3

x mol of N2 ----- 20.8 mol of NH3

2x = 20.8

x = 10.4 mol of N2

3) Now we use the molar mass of N2 to find the quantity in grams that we need to start with:

molar mass N2 = 2x14 = 28 g/mol

Now we use the following equation:

mass = mole × molar mass

mass = 10.4 × 28 = 291.2 grams of Nitrogen Gas

Answer: 291.2 grams of Nitrogen Gas

To answer this question, the first step is to convert the given number of molecules to moles using Avogadro's number:

Now, use the molecular weight of CO2 to find the mass of this amount of moles:

The mass of 5.32x10^22 molecules of CO2 is 3.872g.

Answer

c) C₈H₁₈

Explanation

Given that:

A compound has a molecular weight of 114.22 g/mol

The empirical formula for the compound is C₄H₉

What to find:

To determine the molecular formula for the compound.

Step-by-step solution:

(Empirica formula)n = (Molecular weight)

(C₄H₉)n = 114.22

(4 x 12.01 + 9 x 1.01)n = 114.22

(48.04 + 9.09)n = 114.22

57.13n = 114.22

Divide both sides by 57.13

n = 114.22/57.13

n = 2

Therefore, the molecular formula for the compound is (C₄H₉)₂ = C₈H₁₈

The correct answer is option c) C₈H₁₈

In order to properly balance an equation, we need to make sure that the same amount of elements on the reactants side matches the number of elements on the products side, we can do that by increasing the number in front of each molecule, the so called stoichiometric coefficient. In the reaction from the question we can properly balance by adding the following stoichiometric coefficients

For our question, we have:

2 Al + 3 Zn(NO3)3 -> 2 Al(NO3)3 + 3 Zn

Now this reaction is properly balanced

Al(NO3)3 has the coefficient 2

Answer

1.775 M

Explanation

Given:

Volume of solution, V = 400.0 mL

Mass of NaCl = 45.5 g

What to find:

The molarity of the solution.

Step-by-step solution:

Step 1: Convert the volume from mL to L.

This can be done by dividing the volume in mL by 1000.

V = 400.0 mL = (400.0/1000) = 0.4L

Step 2: Convert the mass of NaCl to moles.

The mass can be converted to moles using the mole formula below:

From the periodic table, the molar mass is determined to be = 58.44 g/mol

Putting mass = 41.5 g and molar mass = 58.44 g/mol into the formula, we have:

Step 3: Calculate the molarity of the solution using the molarity formula.

Molarity formula is given by:

Moles= 0.7101 mol and V = 0.4 L

Therefore,

The molarity of a 400.0 mL solution that contains 41.5 g of NaCl = 1.775 M.

Answer:

Explanation:

Here, we want to identify the elements in BeSO4 in their standard state as the reactants and BeSO4 as the product

From what we have, there are 4 atoms of oxygen, 1 atom of Beryllium, and 1 atom of sulfur

In their standard state, oxygen is a gas, Berrylium and Sulfur are solids

The number of elements atom on the reactant side must be equal to that on the product side

Thus, we have the correct choice of answer as E

option A is  is a true molecular equation depicted.

Na2S+2HCl→2NaCl+H2S↑

A molecular equation is a balanced chemical equation in which the constituent ions of the ionic compounds are represented as molecules. Each of a compound's constituent components and the amount of atoms they each possess are listed in the molecular formula. Similar rules apply to the most basic formula: all the constituents are mentioned, but the numbers represent their relative proportions.

There are three different types of equations that may be developed for a reaction involving ionic compounds: molecular equations, full ionic equations, and net ionic equations. In chemistry, each of these equations has a specific function. Because it details exactly which compounds were employed in a process, a molecular equation is useful.

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0.268grams

According to the Avogadro's constant

1 mole of an atom = 6.02 * 10^23 molecules

Given the following

atoms of calcium = 4.02 x 10^21 atoms

Determine the moles of calcium

Determine the mass of Calcium

Hence the required grams in 4.02 x 10^21 atoms of calcium is 0.268grams

If 5750 J of energy are added to 455 g of granite at 24 °C. The final temperature of granite is 39.9 °C

Given that :

heat energy = 5750 J

mass of granite = 455 g

initial temperature = 24 °C

specific heat capacity = 0.12 cal / g °C = 0.790 J/ g °C

the expression for the heat capacity is given as :

Q = mcΔT

5750 J = 455 g × 0.790 J/ g °C ( T - 24 °C)

5750 = 359.45 T - 8626.8

T = 39.9 °C

if 5750 J of energy are added to 455 g of granite at 24 °C. The final temperature of granite is 39.9 °C

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Explanation:

Ammonia will decompose into nitrogen gas and hydrogen gas according to the following reaction. In that reaction 92 kJ will be absorbed.

2 NH₃ ----> N₂ + 3 H₂ ΔH = 92 kJ

Since the heat is absorbed, the sign is positive and we can add it to the reactants side.

2 NH₃ + 92 kJ ----> N₂ + 3 H₂

When 92 kJ are absorbed 34 g of ammonia are reacted. We can use that relationship to find the mass of ammonia that reacted when 184 kJ where absorbed.

34 g of NH₃ : 92 kJ

mass of NH₃ = 184 kJ * 34 g of NH₃/(92 kJ)

mass of NH₃ = 68 g

Answer: 68 g of ammonia were decomposed.

2 NH₃ ----> N₂ + 3 H₂ ΔH = 92 kJ

ANSWER

False

EXPLANATION

Electron affinity is defined as the energy released by adding an electron to an isolated gaseous atom

Neon has the electronic configuration of 2, 8, This implies that it belongs to period 2 and group 8

Recall, that Neon is a noble gas. Noble gases do not accept or release electrons.

Hence, neon does not have the tendency to accept or release electrons.

Neon as a noble gas has a large positive value for electron affinity

Therefore, the statement is not TRUE

It can lower and expand the melting point if the sample is not dried completely.

Impurities may be present in a sample if the drying process is not complete. The melting point is decreased and widened when contaminants are still present in a sample. For instance, if a substance's usual melting point range is 104C to 106C, improper drying could result in the presence of impurities, which would lower and widen the melting point range to something like 85C to 97C.

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In the process that they describe to us, a mixture initially occurs between these two liquids, when they are mixed, a chemical reaction occurs and one of the products obtained is not soluble in the liquids, therefore a precipitate will form. This type of reaction is called a precipitation reaction.

Therefore, the answer will be:

C) Have gone through a chemical reaction in which a new substance called a precipitate was produced

This is a stoichiometry problem, where we have an initial amount of reactant and we need to find out how much of the product will we end up with, in order to do that we need to:

1. Set up the properly balanced equation, which the question already provided us

2 KClO3 -> 2 KCl + 3 O2

2. Check the molar ratio between the two compounds, which is 2:3, 2 moles of KClO3 will produce 3 moles of O2, but we have 3 moles of KClO3

2 KClO3 = 3 O2

3 KClO3 = x O2

x = 4.5 moles of O2 will be produced from 3 moles of KClO3

3 KClO3

2 KClO3/ 3 O2

4.5 O2

Answer: By using Ideal gas law  PV=nRT  ,the final pressure is calculated

Explanation:

In thermodynamics a constant volume process is known as isochoric process and in this volume remains constant and pressure varies along with the temperature .

FORMULA USED - PV=nRT

If Volume is constant ,then  initial Temperature  = 18+273 = 291K

final temperature =225K

initial pressure = 0.90 atm

final pressure = ?

The final pressure comes out to be 0.6958 atm.

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To calculate the molar mass of NaHCO₃, we need to add the molar mass of each of its atoms.

This compound has 1 atom of Na, 1 of H 1 of C and 3 of O.

The molar mass of these atoms can be consulted on a periodic table, and they are:

So, the molar mass of NaHCO₃ is:

answer and explanation

we are given the [OH] concentration as 6.25*10-12

and we know that

[H+][OH-] = 1.0*10^-14

an so using this relationship we can determine the [H+]

[H+][6.25*10-12] = 1.0*10-14

[H+] = 0.0016M

Considering the ideal gas law, the pressure in a 7.00 L tank with 1.73 grams of hydrogen gas at 375 K is 26.5987 atm.

An ideal gas is called a hypothetical or theoretical gas, which would be composed of particles that move randomly and without interacting with each other.

An ideal gas is characterized by three state variables: absolute pressure (P), volume (V), and absolute temperature (T). The relationship between them constitutes the ideal gas law, an equation that relates the three variables if the amount of substance, number of moles n, remains constant and where R is the molar gas constant:

P×V = n×R×T

In this case, you know:

Replacing in the definition of ideal gas law:

P× 2 L = 1.73 moles ×0.082 atmL/molK ×375 K

Solving:

P= (1.73 moles ×0.082 atmL/molK ×375 K)÷ 2 L

P= 26.5987 atm

Finally, the pressure is 26.5987 atm.

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5s. Option D is correct

Electron orbitals are area around the nucleus where electron resides. The closer the orbital to the nucleus, the higher the energy level.

Based on the explanation above, 5s will be higher in energy than the 4d orbital.

Since the operation is a multiplication, the order in which we made the multiplications doesn't matter, so we can reoprder it:

Now, we calculate each of them:

DNA describes as a blueprint for a cell because it contain the instruction needed for an organism to grow develop and survive

DNA is called a blueprint of life because it contain the instruction needed for an organism to grow develop and survive and reproduce and DNA does this by controlling protein synthesis and protein do must of the work cell and are basic unit of structure and function in the cell of organism

DNA is read by the enzyme RNA polymerase and this enzyme attaches itself to the DNA strand slightly in front of a gene and it then slides along the DNA strand making a copy of the gene only using RNA building blocks instead of DNA building block

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Answer:

I believe it is

C. density

Explanation:

have a nice day!❀

The Lewis structure tells us how atoms are bonded and shows the valence electrons of each element as dots. These valence electrons can be found in the periodic table of the elements, and they coincide with the group number to which the element belongs.

So phosphorus (P) belongs to group 5 and has 5 valence electrons. Chlorine (Cl) is in group 7 and has 7 valence electrons.

The Lewis scheme will be:

The blue dots correspond to the valence electrons of phosphorus, and the purple dots are the electrons of chlorine. The electrons they share can be written with a line.

We have that the geometry of the molecule will be:

Four sp3 type hybrid orbitals are formed, three of which overlap with each of the Cl atoms and the other houses the lone electrons. Sigma type bonds.

Answer: 4 sp3 hybrid orbitals