Limestone is a sedimentary rock composed largely of the mineral calcite, (calcium carbonate) CaCO3. To test the purity of the calcium carbonate, a sample of the mineral is reacted with hydrochloric acid to produce calcium chloride, carbon dioxide and water If a 15.70 g sample of calcite is reacted with excess hydrochloric acid and 16.89 g of calcium chloride are produced, what is the percent by mass of the calcium carbonate in the limestone? A) 69.4% B)93.0 % C) 96.94% D)98,22 %

answer and explanation

Radioactivity is the emission of ionizing radiation from nuclear decay. there are three types of radioactive decay.

alpha decay

in alpha decay an alpha particle is released. In the parent atom, the atomic number decreases by 2 and the atomic mass decreases by 4

beta decay

in beta decay a beta particle is released, the atomic number is unchanged and the atomic mass increases by 1

gamma decay

in gamma decay, energy is released as gamma rays from an excited nuclear state. the atomic mass and atomic number remain unchanged.

A ionic compound is made of two ions, one with positive charge and the other one with a negative charge.

The ion with positive charge is known as cation and the one with negative charge is known a anion.

It means that the correct answer is A. A positive cation and a negative anion.

The decay of this radioactive unknown compound is a first-order process.

We can express the time dependence of its mass m using a first-order integrated rate law, where k is the rate constant:

mt = mass at time t

m0 = initial mass

t = time

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Procedure:

1) We need to find "k":

From the first-order rate law we clear k,

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2) We find the half-life from the value of k we have just calculated:

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3) The number of half-lives of the unknown sample is:

Number of Half-lives = 47 days / 15.7 days = 3 (approx.)

Answer: Number of half-lives = 3

Kinect-molecular theory hypothesis:

- The formation of a gas occurs by a large number of molecules;

- Gas molecules have a negligible dimension, which means that the volume occupied by them is very small, almost insignificant;

- These gases move in a discontinuous and random way, thus occupying the entire volume of the container where they are found, having a rectilinear and uniformly varied movement;

- They are independent, they only interact with each other when a collision occurs;

- Collisions between molecules and molecules and between molecules and container walls are elastic collisions, which cause the kinetic energy of the molecules to remain constant.

Having seen these statements, the answers can only be:

The warmer a glass of water, the faster a drop of ink will spread through the water.

The colder a room is, the longer it would take to smell a spray of perfume from the other side of the room.

0.2 grams

The balanced reaction between zinc and hydrochloric acid is given as:

Given the following parameters

Mass of Zinc = 6.5grams

Determine the mole of Zinc

Mole of Zn = mass/molar mass

Mole of Zn = 6.5/65.38

Mole of Zn = 0.0994moles

According to stoichiometry, 1 mole of Zinc produced 1 mole of hydrogen gas, hence the mole of hydrogen gas required will be 0.0994moles

Determine the mass of hydrogen gas produced

Hence the mass of hydrogen that were released is 0.2 grams

To solve this problem we can use the Ideal gas law:

The problem give us de following information:

P1= 131kPa

V1=1.82L

T1=-30°C= 243.15 K

P2= 233 kPa

V2= 1.3L

Then we just have to solve for T2 and use the information provided:

Then the answer is T2=35.76°C

If you only have the percent composition of each element in a give compound, you can't determine yet the empirical formular for the compound. The problem is, the percent composition only gives relative numbers for each element. What can be determined is the empirical stochiometry of one element relative to the others.

For example, supose you have a compound with element X and Y, with the percent composition you can determine how much X you have relative to how much Y you have. Say you determine that for each 2 X you have 3 Y, the formula can be X₂Y₃ but it can also be X₄Y₆ or even othre possibilities.

To determine the empirical formula you need to know how many of one of the elements you have in each compound. A common way of getting the empirical formula is to use the percent composition and, in addition, the molar mass of the compound, which will make it possible to get the empirical formula from the relative ratios of each element you have.

The mass of the copper that is obtained is 97.2 tons.

We can define the term combustion as the procedure by which a substance can be burnt in oxygen. We can also be able to refer to the process as roasting the object in the air. It is an oxidation reaction.

Having said all all of these, the reaction equation can be written as;

[tex]Cu_{2} S + O_{2} ------ > 2Cu + SO_{2}[/tex]

We know that the percent of the copper that it contains can now be used when we are trying to compute the mass of the copper that can be obtained from the process as we are going to have in the question that is at hand here to solve.

We are now going to proceed to see the mass of the copper that can be produced from the 300 tons of the copper I sulfide ore given.

Thus;

The mass of copper that can be obtained is;

3.24/100 * 3000 tons

= 97.2 tons

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Answer:

Percent yield = 27.3%.

Explanation:

First, let's write the chemical equation:

The limiting reactant, in this case, would be O2 because we have an excess of ZnS. So, we have to convert 42.5 g of O2 to moles. Remember that the molar mass of O2 is 32 g/mol (you can calculate the molar mass of a compound using the periodic table). The conversion will be:

With this value, we're going to find the number of moles of SO2 produced by 1.33 moles of O2. You can see in the chemical equation that 3 moles of O2 reacted produces 2 moles of SO2, so the calculation would look like this:

The next step is to find the mass of SO2 based on its number of moles and the molar mass of SO2 which is 64 g/mol, like this:

And finally, we replace the values that we have in the formula of percent yield:

Our experimental yield is the mass that we obtained of SO2 which is 15.5 g and the theoretical yield is the mass that we found through stoichiometry which is 56.8g:

The percent yield of this reaction would be 27.3%

The polarity of a molecule is given by the difference in charges, hydrogen has a slightly positive charge and oxygen has a negative charge. Its electronegativity difference between hydrogen and oxygen is less than 1.7 making the bond a covalent bond.

That said, we can rule out options A and D. Now, the state of matter does not affect the polarity of the molecule, so option B will also be incorrect.

The correct option will be C, since there is a difference in charges that makes water polar.

Answer: C) The uneven bend in the bond between oxygen and hydrogen

The question requires us to calculate the number of moles of each element (magnesium, chlorine and oxygen) in 8.30 moles of the compound magnesium perchlorate (Mg(ClO4)2).

From the molecular formula of magnesium perchlorate we can take the following information:

- in 1 mol of Mg(ClO4)2, there is only 1 mol of Mg;

- in 1 mol of Mg(ClO4)2, there are 2 moles of Cl;

- in 1 mol of Mg(ClO4)2, there are 8 moles of O.

With the information above, and knowing that the amount of Mg(ClO4)2 given by the question was 8.30 moles, we can calculate the amount, in moles, of each element:

1 mol Mg(ClO4)2 --------------- 1 mol Mg

8.30 mol Mg(ClO4)2 ---------- x = 8.30 mol Mg

1 mol Mg(ClO4)2 --------------- 2 mol Cl

8.30 mol Mg(ClO4)2 ---------- y = 2 x 8.30 mol Cl = 16.6 mol Cl

1 mol Mg(ClO4)2 --------------- 8 mol O

8.30 mol Mg(ClO4)2 ---------- z = 8 x 8.30 mol O = 66.4 mol O

Therefore, there are 8.30, 16.6 and 66.4 moles of Mg, Cl and O in 8.30 moles of magnesium perssufate.

1. Synthesis reaction : there is only 1 product formed from 2 or more reactant

E.g:

2. Decomposition : reaction that occurs in presence of UV light and only 1 reactant that decomposes into 2 or more products.

E.g:

3. Single displacement : reaction that occurs when 1 reactant displaces other reactant from its compound:

E.g:

4. Double displacement : reaction that occurs when both reactant displaces each other.

E.g :

Explanation

There are said to have two different conditions of a gas.

First condition is STP which means: pressure = 1 atm and temperature (absolute) = 0 °C + 273 = 273 K

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It is said that the temperature remains constant, therefore we can apply Boyle's law which states that the pressure of a gas tends to decrease as the volume of the container increases.

Answer:

The Arrhenius acids in the list are:

HCl, HBr , H2SO4 , H3PO4 , HNO3 , HF

The Arrhenius bases are:

NaOH , NH4OH , LiOH , Ba(OH)2 , CsOH and KOH

Explanation:

An Arrhenius acid increases the concentration of H+ ions while an Arrhenius acid increases the concentration of OH- ions

Thus, an Arrhenius acid would yield H+ ions on ionization while an Arrhenius base will yield OH- ions on ionization

The Arrhenius acids in the list are:

HCl, HBr , H2SO4 , H3PO4 , HNO3 , HF

The Arrhenius bases are:

NaOH , NH4OH , LiOH , Ba(OH)2 , CsOH and KOH

Avogadro's number states that:

1 mol of Cu = 63.54 g of Cu = 6.02x10^23 atoms of Cu

Now, we proceed like this:

1 kg = 1000 g ===> 187 kg = 187,000 g

63.54 g Cu -------- 6.02x10^23 atoms of Cu

187,000 g Cu -------- X

X = 1.77x10^27 atoms Cu

Answer: 1.77x10^27 atoms Cu

According to the explanation about oxidizing and reducing agents from the previous session, we will find the answers to this question as well

Oxidation numbers are mostly found in previously made tables, there are plenty of tables where you can see the oxidation numbers for almost every element, a few rules to have in mind is H is usually +1, O is -2, Halogens are -1, group 1A metals are +1, transition metals are the ones that will shift a lot

1. Sn + 2 HCl -> SnCl2 + H2, this is the properly balanced equation

REACTANTS

Sn = 0, since it's a lone element in the reaction we assume its charge is 0 because is stable

H = +1

Cl = -1, it's a halogen

PRODUCTS

Sn = +2, we see now that Sn was oxidized and now has a positive charge

Cl = still -1

H2 = 0, was reduced, now with a 0 charge

2. 2 NaBr + Cl2 -> 2 NaCl + Br2

REACTANTS

Na = +1, metal from group 1A

Br = -1, halogen

Cl2 = 0 stable element

PRODUCTS

Na = +1

Cl = -1, it will be reduced

Br = 0, it will be oxidized

3. SiCl4 + 2 Mg -> 2 MgCl2 + Si

REACTANTS

Si = +4

Cl = -1

Mg = 0

PRODUCTS

Mg = +2, it will be oxidized

Cl = -1

Si = 0, it will be reduced

Molarity or molar concentration is a measure of the concentration of a chemical species, of a solute in a solution, using as units, number of moles, and volume in liters. The formula for Molarity is:

M = n/V

Where:

n = number of moles

V = volume in Liters, 1 Liter

But we need to find the number of moles, we will do so by using its molar mass, KI = 166g/mol and the given mass in the question, 500g grams

166g = 1 mol

500g = x moles

x = 3.012 moles

Now we can use the Molarity formula

M = 3.012/1

M = 3.012 M, this is the molar concentration of the solution, 2

Explanation:

First, let's write the balanced equation of formation of MgCl2 from Mg and Cl2:

Mg + Cl2 → MgCl2

Now let's transform 10.0g of Mg into moles, using the following formula: moles = mass/molar mass

molar mass of Mg = 24.3 g/mol

moles = 10/24.3

moles = 0.412 moles

Now we use the equation ratio between Mg and MgCl2 to find the quantity of MgCl2 in moles.

1 mole of Mg produces 1 mole of MgCl2.

So 0.412 moles of Mg produces 0.412 moles of MgCl2.

Now we transform 0.412 moles of MgCl2 into mass using the following formula: mass = moles x molar mass

Molar mass of MgCl2: 24.3 + (2*35.45) = 95.21 g/mol

Mass = 0.412 * 95.21

Mass = 39.2 g

Answer: The theoretical yield of MgCl2 is 39.2 g.

For each particle (molecule) of Ca(OH)2 that was present, assuming full dissociation of the complex, you would get two particles (ions). CaO + H2O equals Ca(OH)2 (2 particles)

A 0.561 M solution contains 0.561 moles of Ca(OH)2 per kilogram of solvent. Ions' molality would be 2 x 0.561m = 1.122m.

The most used unit for expressing solution concentration is molarity (M), which is calculated by dividing the solute concentration in moles by the volume of the solution in liters: M stands for moles of solute per liter of solution.

The kilograms of solvent divided by the moles of ions in the solution is the molality. As an illustration, if You will have 1.0 molal concentration of sodium chloride, for instance, if 1.0 moles of sodium chloride are dissolved in 1.0 kilogram of solution.

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Answer:

Atoms

Explanation:

Answer:

atoms

Explanation:

its right, trust

Answer

0.0779 g SO₃

Procedure

To solve this question, you will need to use the Avogadro's number equivalent to 6.02214 x 10^23 molecules/ mol, and then the molecular weight in grams per mole for the SO₃.

Ne is a noble gas, O is a non metal and Br is an halogen.

K is a metal that belongs to the same group as Na, it means that they have similar chemical properties.

It means that the answer is K.

Answer:

Explanation:Consider the balanced thermochemical equation given below: AH = -125.9 kJ W(s) + 3 H2O(g) WO3(s) + 3 H2(g) If a mass of 94.6 g H2 is produced, what is the enthalpy change? Express your answer in kJ. Express your answer to the correct number of significant figure, in scientific notation and include the unit with

1) Chemical equation

2) Moles of CO2 produced oxygen reacts

The molar ratio

2 mol O2: 1 mol CO2

If 36 mol O2 reacts, it will produce 18 mol CO2.

.

To answer this question we have to compare the specific heats of each substance.

The specific heat of a substance is the amount of energy required to make 1 gram of a substance increase its temperature by 1 °C. The greater the specific heat of a substance the more energy it will be required to heat it up.

The specific heat of water is 4.18J/g°C and the specific heat of aluminum is 0.897J/g°C.

It means that the amount of energy required to heat water is greater than the one to heat aluminum.

It means that the answer is TRUE.

Hydrogen bonding is formed when the partial negative charge at one end of a water molecule is attracted to the partial positive charge of another water molecule

Thus, when the partial negative charge at one end of a water molecule is attracted to the partial positive charge of another water molecule, hydrogen bonding is formed.

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Answer:

C

Explanation:

Because the suspect touched something at the crime scene and thus he's fingerprint are matching

Structural formulas are ways atoms and elements are arranged in a molecule. The structural formula of pentane, pentene, and pentyne are as shown below;

Pentane - C5H12

Pentene - C5H10

Pentyne - C5H8

e) Pentane is an alkane compound with a general formula CnH2n+2. The chemical formula of pentane is C5H12. There are only single bonds between the C-H atoms in the molecule.

Pentene is an alkene compound with a general formula of CnH2n. The chemical formula of pentene is C5H10. There is a double bond present between the C=H atoms. This double bond shows that the compound is an alkene.

Pentyne is an alkyne compound with a general formula of CnH2n-2. The chemical formula of pentene is C5H8. There is a triple bond present between the Carbon Hydrogen atoms. This presence of a triple bond shows that the molecule is an alkyne compound.

Step 1

The reaction must be completed and balanced:

4NH3 (g) + 9O2 (g) => 4NO3 + 6H2O (g)

Reactants: NH3 and O2

Products: NO3 and H2O

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Step 2

Information provided:

STP conditions, therefore:

1 mole of gas (NH3 in this case) = 22.4 L (volume)

5.3 g of O2

Liters => L

Grams => g

---------

Information needed:

The molar mass of O2 = 32.0 g/mol

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Step 3

By stoichiometry,

1 mole NH3 = 22.4 L NH3

1 mole O2 = 32.0 g O2

Procedure: We will work with volume and mass

4NH3 (g) + 9O2 (g) => 4NO3 + 6H2O (g)

4 x 22.4 L NH3 ---------- 9 x 32.0 g O2

X ----------- 5.3 g O2

X = 5.3 g O2 x 4 x 22.4 L NH3/9 x 32.0 g O2 = 1.65 L approx.

Answer: 1.65 L of NH3