Three students (A, B, and C) are asked to determine the volume of a sample of water. Each student measures the volume three times with a graduated cylinder. The results in milliliters are: A (87.1, 88.2, 87.6); B (86.9, 87.1, 87.2); C (87.6, 87.8, 87.9). The true volume is 87.0 mL. Comment on the precision and the accuracy of each student’s results. aStudent A has results that are neither precise nor accurate. bStudent B has results that are both precise and accurate. cStudent C has results that are precise but not accurate. dStudent A has results that are precise and accurate. eStudent B has results that are neither precise and accurate. fStudent C has results that are accurate but not precise.

Answer:

Na2S2O3.

Explanation:

What is given?

If we suppose that the compound has a mass of 100 g:

Mass of Na = 29.1 g,

Mass of S = 40.5 g,

Mass of O = 30.4 g,

Molar mass of Na = 23 g/mol,

Molar mass of S = 32 g/mol,

Molar mass of O = 16 g/mol.

Step-by-step solution:

First, we have to convert all the given masses of each element to moles using their respective molar mass, like this:

The next step is to divide each number of moles by the least number of moles obtained, which in this case is 1.27, as follows:

Remember that we need to have the number of moles of each element as integers, so if we multiply each number of moles of each element by 2, we will obtain:

We would have 2 mol of Na, 2 mol of S, and 3 mol of O, so the empirical formula is Na2S2O3

1) Uncertainty in substraction. the result must have the same number of decimal places as the one with less.

5.1 - 2.3685 = 2.7315

The result must have one decimal place. Since the second decimal place (3) is smaller than five we round down.

The result is 2.7.

For solving this exercise we need the molar mass of CuNO3 which is 125.5 g/mol

Step 1) We calculate the moles of this compound:

8.54 g CuNO3 / 125.5 g/mol = 0.0680 moles CuNO3

Step 2) We calculate the volume of the solution in L:

(Remember M is equal to mol/L)

0.0680 moles CuNO3 / 0.520 mol/L = 0.131 L

Step 3) We change L to mL:

(Remember 1L=1000mL)

0.131 L x (1000mL/1L) = 131 mL

Answer: Volume = 131 mL

Step 1 - Understanding the relation between pressure and volume

There are three main variables that can modify the state of a gas: pressure (P), temperature (T) and volume (V). When one of them is kept constant, linear relationships arise between the other two variables, i.e., proportionality relations.

When the temperature is kept constant (isothermic transformation), the pressure and the volume become inversely proportional, i.e., increasing the pressure reduces the volume.

We can state it mathematically as:

Step 2 - Using the equation to solve the exercise

To calculate the new volume (V2), we can use the equation. The values we need are given in the exercise:

Substituting these values in the equation above, we have:

The final volume would be thus 8.2L.

The terms excess reactant and limiting reactant refer to how much of each reactant is available to react. Therefore, by its name we can understand that limiting reactant really limits the reaction, that is, it determines how much product can be made (B).

Excess reactant is also very literal, as it refers to the reactant in excess, that is, the one that is not all used up in the reaction (C).

And Theoretical yield refers to the amount of product that is produced based on the amount of reactants that really react, that is, the amount of product that can be made by the given amount of reactants (A)

In conclusion,

A) Theoretical yield.

B) Limiting reactant.

C) Excess reactant.

In this question, at STP (standard temperature and pressure) it is conventional to assume that 1 mol of a substance is equal to 22.4 Liters of volume, therefore, if we have 2 moles of Hydrogen gas:

1 mol H2 = 22.4 L

2 moles H2 = x L

x = 44.8 Liters of volume

4Fe + 3O2 ==> 2Fe2O3

Step 1 - Understanding the stoichiometry of the reaction

The given reaction is:

Note that 1 mole of Nitrogen gas react with 2 moles of Oxygen gas thus producing 1 mole of N2O4 gas. Since this is a fixed relation, we can state that:

each 2 moles of O2 produce 1 mole of N2O4

Step 2 - Converting the relation in moles to a relation in grams

We can convert the relation in moles between O2 and N2O4 to a relation in grams by multiplying each number of moles by the respective molar masses of the substances (32 g/mol for O2; 92 g/mol for N2O4):

We can state therefore that:

64 g of O2 (2 moles) produce 92 g of N2O4

This is like a cake recipe. It is a fixed proportion in grams, and we'll be using it to solve the exercise.

Step 3 - Finding the required moles of O2

Now that we have found a "recipe" for the reaction, we can use it to predict how much O2 would be needed. Let's remember that, in step 2, we have discovered that 2 moles of O2 produce 92 g of N2O4.

Therefore, to produce 23.6 grams, we can set the following proportion:

Therefore, 0.51 moles of O2 would be required.

Ok to answer this question we firsst need to fin the number of mol of Urea (CH4N2O). to do this we simply :

1 mol of urea =15/60.055 = 0.25mol

therefore 200g of water contain 0.25mol

the next step is to determine the malality of our solution in 200g of water, to do this we say:

200 g = 1Kg/1000g = 0.2kg

therefor 0.25mol/0.2Kg = 1.25mol/kg

and from the equation:

we know that i = 1

we are given Kf

b is the molality that we just calculated

therefore;

the solutions freezing point is -2.325°C

The freezing point of the given solution was calculated to be -2.325 °C. The freezing point is the point at which a liquid changes from a liquid to a solid under atmospheric pressure.

The two phases, liquid and solid, exist in equilibrium at the freezing point. At the freezing point, both solid and liquid exist at the same time.

Given,

15 grams of CH₄N₂O is dissolved in 200 grams of water.

1 mol of urea = 60 grams

so 15 grams of urea will be found in 15/60 = 0.25 moles

So 0.25 moles of urea is present in 200 grams of water.

To determine the molality of the solution

200gm/1000gm = 0.2 kg water

0.25 moles/0.2 kg = 1.25 kg/mol

So to calculate the freezing point of the solution we use the formula:

ΔT = i× Kf × b  

Given Kf = 1.86 (°C·kg)/mol), b is the molality of the solution that is = 1.25 kg/mol, and i = 1

ΔT = 1 ×  1.86 × 1.25 = 2.325 °C

ΔT  = 0 °C - 2.325 °C =  -2.325 °C

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The equation 2 C₂H₆ + 7 O2 ⇒ 4 CO₂ + 6H₂O. 482.6 gram of H₂O are produced from 268.5 grams of C₂H₆.

A saturated hydrocarbon that exists in a gaseous form is ethane. Methane is the simplest alkane, with ethane coming in second. It has 6 hydrogen atoms and 2 carbon atoms. Ethane's chemical formula is CH

With the chemical formula C₂H₆, ethane is an organic chemical substance. Ethane is a colorless and odorless gas at ordinary temperature and pressure.

Ethane is separated from natural gas on an industrial scale, and it is produced as a by-product of the petrochemical process used to refine crude oil.

268.5 gram of C₂H₆ × ( 1 mole C₂H₆ ÷ 30.07 gram of C₂H₆ ) × ( 6 mole of H₂O ÷ 2 mole C₂H₆ ) × ( 18.015 gram of H₂O ÷ 1 mole of H₂O )

= 482.6 gram of H₂O.

Thus, the equation 2 C₂H₆ + 7 O2 ⇒ 4 CO₂ + 6H₂O. 482.6 gram of H₂O are produced from 268.5 grams of C₂H₆.

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Explanation

A) Trigonal planar

B) Trigonal pyramid

C) Tetrahedral

D) Linear

E) Linear

F) Tetrahedral

G) Linear

INFORMATION:

We know that:

- 35 ml of liquid has the mass of 41.6 g

And we must find its density

STEP BY STEP EXPLANATION:

To find it, we must use the following formula

From given information:

- mass of the liquid: 41.6 g

- volume of the liquid: 35 ml

Now, replacing the values in the formula

Finally, the density of the liquid is 1.19 g/ml

ANSWER:

The density of the liquid is 1.19 g/ml

Le Chatelier's principle is used to determine what effect a change will have on a mixture at equilibrium.

It describes the effect that a mixture suffers when it is exposed to a change.

It means that the correct answer is A.

5.38 g is the mass of iron (0.444 J/goC) that can be heated from 5.4°C to 22.8°C using +41.6 J of energy

q=+41.6 J

c=0.444 J/goC

Δt=17.4

q=mcΔt

m=q/cΔt

m=+41.6 J /0.444 J/goC×17.4

m=5.38 g

Mass is one of the fundamental quantities in chemistry and the most fundamental property of matter. The quantity of matter in a body is referred to as its mass. The SI unit of mass is the kilogram.

The mass of a body is constant at all times. only when a body receives or loses a considerable amount of energy, which happens seldom. For instance, a nuclear reaction causes the mass of the material to decrease because a very little amount of matter is converted into a very high amount of energy.

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To answer this question, we have to use the following formula:

Where Q is the heat, Cp is the specific heat, m is the mass and ΔT is the difference in temperature.

In this case, we know the heat, the mass and the difference in temperature and we need to find the specific heat. Solve the given equation for Cp:

Replace for the given values and solve:

It means that the specific heat of the metal is 0.076J/g°C.

Answer

Synthesis

Explanation

Synthesis reaction is when reactants combine to

The definition of wavelength is the distance between two identical points, like the crests of the waves, in a cycle of a waveform, so the distance between two crests, which is the highest point of the wave, this is wavelength

In our question, we have that one crest starts at 1.5 cm and the other starts at 2.5 cm, therefore the wavelength will be 1.0 cm of distance, letter D

1) List the known and unknown quantities.

Molar mass: 34.04 g.

Empirical formula: NH.

Molecular formula: unknown.

2) Find the molar mass of the empirical formula.

N: 14.007 g/mol.

H: 1.008 g/mol.

N + H = 14.007 + 1.008 = 15.015 g/mol.

3) Divide the molar mass by the molar mass of the empirical formula

Multiply the subscripts of the empirical formula by 2.

.

For this reaction we have to look at which compound will be a solid at the end, this means that this specific compound is not soluble in water, therefore forming a precipitate

3 Li2CO3 (aq) + Al(NO3)3 (aq) -> 6 Li(NO3) (aq) + Al2(CO3)3 (s)

As we can see in the balanced reaction, we will have Al2(CO3)3 as a solid product from this reaction, therefore it will be forming a precipitate

Answer: D

In this case you need to use the volume and temperature equation from Charles law.

We are given T1 = 139 k

T2= 317 k

V2= 176 L

We want to find V1. Now lets re-arrange the equation.

V1 = (176 x 139)/317

V1= 77.2 L

Answer:

Explanation:

Here, we want to get what happens to the phases of water as the temperature is decreased at 5 atm

From what we have in the question, we would be moving from left to right

What would happen here is that we move from the gaseous state to the liquid and then to the ice state

This means we have a change from a gas to a liquid then a solid

So,

First of all, let's remember what physical and chemical changes are.

A physical change occurs when there's changes in the size or shape of matter. Changes of state, for example, from solid to liquid or from liquid to gas, are also physical changes. In this kind of change, the composition of the matter doesn't change.

A chemical change occurs when a substance combines with another to form a new substance, and the composition of the matter changes.

Now that we know what these changes are, we could give some examples of a physical change in cooking, for example:

1. Suppose we want to serve a freezed drink, like a popsicle. For this, we could freeze a fruit juice. This is a physical change because the composition of the juice changes from liquid to solid.

2. Suppose we want to serve pasta. We need to boil the pasta to make it soft, which is a physical change clearly.

3. Suppose we want to serve meat but this is freezed, so, we need to thaw it to start cooking, which is a physical change.

Boron gas can achieve  noble gas configuration by losing or gaining electrons.

Noble gases were substances that have completed respective octets and have entirely filled respective valence shells. Helium (He), Neon(Ne), Argon(Ar), Krypton(Kr), Xenon (Xe), as well as Radon, are still examples of noble gases.

Atoms can adopt a noble gas configuration whether by acquiring new electrons or by giving and receiving electrons already present in even their own outermost shell.

The atomic number of Boron is 5 . the electronic configuration of B is 2,3. When it will gain 5 electrons with another atom or lose 3 electrons then it will attain a noble gas configuration.

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Explanation

A combustion reaction is a type of chemical reaction in which a compound and an oxidant are reacted to produce heat and a new product. The general form of a combustion reaction can be represented as follows:

Hydrocarbond + O2 => CO2 + H2O

In addition to heat (also common)

Answer: a combustion reaction

In this question, we have the following reaction:

6 HCl + 2 Al -> 2 AlCl3 + 3 H2

We have:

250 mL of HCl

2.5 g of Al

And we want to find the molar concentration of HCl

One way of doing it is by finding the number of moles of HCl present in this solution, we can do that by using the number of moles of Al and after that, comparing the molar ratio of HCl and Al. To find the number of moles of Al, we will use its molar mass 27g/mol

27g = 1 mol

2.5g = x moles

x = 0.0926 moles of Al in 2.5 grams

Now by looking at the properly balanced reaction, we can see that the molar ratio between HCl and Al is 6:2, so if we have 0.0926 moles of Al, we will have:

6 HCl = 2 Al

x HCl = 0.0926 Al

x = 0.2778 moles of HCl

Now that we have the volume and the number of moles, we can find the molar concentration of HCl, using the Molarity formula:

M = number of moles/volume in liters

M = 0.2778/0.250

M = 1.11 is the molar concentration of HCl in this given solution

The speed of Mercury around the sun is 47 Km/s while the speed of Saturn around the sun is 9.69 Km/s. Therefore, Mercury orbits the Sun at a speed more than four times the speed of Saturn. Therefore, the given statement is true.

Mercury can be described as the smallest planet in the Solar System and also the closest to the Sun. Mercury orbits around the Sun and takes 88 Earth days. Mercury rotates in a unique way in the Solar System as it is tidally locked with the Sun in a 3 : 2 spin-orbit resonance.

Mercury can be described as a rocky body like Earth with an equatorial radius of 2,439.7 kilometers. Mercury contains approximately 70% metallic and 30% silicate material.

Saturn is the second-largest and the sixth planet from the sun in the Solar System, after Jupiter. Saturn is a gas giant with a radius of about nine and a half times that of Earth. The speed of Mercury orbits the Sun is more than four times the speed of Saturn.

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First, we write our reaction:

Al + Cl2 ==> AlCl3

To balance a reaction similar to this one, we must focus on having the same number of atoms on each side, I mean on the left side and on the right side of the reaction.

As we can see, we have 2 Cl on the left and 3 on the right, therefore we try to have the same number of this atom, multiplying by a pair number and an odd number respectively e.g. by 3 and 2.

Al + 3 Cl2 ==> 2 AlCl3

After that, we have 6 Cl on both sides. Then, we must go on with Al, and the only thing we should do is multiply on the left by 2 because we already have 2 Al on the right side.

2 Al + 3 Cl2 ==> 2 AlCl3

With this, we will have 2 Al and 6 Cl in total

Answer: 2 Al + 3 Cl2 ==> 2 AlCl3

In each 1 gram, we have 1000 miligrams, that is:

1 g = 1000 mg

So, we can use rule of three to find the answer:

x ---- 3.65 g

1000 mg ---- 1 g

Thus:

So, we have:

3.65 g = 3650 mg

A buffer system usually will need a weak acid, like H2CO3, which is carbonic acid, and a strong base, and the only compound that could figure a fairly strong base among the options given is Na2CO3. NH3 and NaHCO3 are weak bases and HF is a strong acid. Therefore the best answer will be letter A