A vessel contains 18.06*10^23 molecules of ammonia gas at 25°c. Calculate the number of hydrogen atoms present in the ammonia gas.

Most regulatory signs are used to control the movement of traffic and they help the people to follow the rules and they are in the shape of vertical triangle

Explanation:

These sign are one that help to regulate the traffic for the traffic direction like the lane use, parking, turning, speed and in other special situation these signs are called as regulatory signs

They are most often in the shape of triangle with a red circle or a red dot in it indicating the signs and the direction in which they must move and the rule that they must not follow

Some of the examples are no right turn, no left turn and no U-turn

Answer:

Low energy waves have a long wavelength.

Explanation:

Energy of wave is directly related to  the frequency while it is inversely proportional to the wavelength.

If any wave have high energy it will have high frequency and smaller wavelength.

If the wave have lower energy then it will have lower frequency and higher wavelength.

Mathematical relationship:

E = h. f

E = h. c/λ

E= energy

h = planck's constant

f = frequency

c = speed of light

λ = wavelength

Answer:

Plates sliding past each other cause friction and heat. Subducting plates melt into the mantle, and diverging plates create new crust material. Subducting plates, where one tectonic plate is being driven under another, are associated with volcanoes and earthquakes.

Explanation:

The correct order for the first three steps of the scientific method is:D. State the question, form a hypothesis, conduct an experiment.

Here is a step-by-step explanation:

1. State the question: This is the first step in the scientific method. It involves identifying a problem or question that you want to investigate. It is important to clearly define the question you want to answer through your experiment.

2. Form a hypothesis: After stating the question, you need to come up with a hypothesis. A hypothesis is an educated guess or prediction that explains the relationship between the variables being studied. It is usually stated as an "if-then" statement, where you propose that if a certain condition is met, then a specific outcome will occur.

3. Conduct an experiment: Once you have a hypothesis, you can design and carry out an experiment to test it. An experiment involves systematically manipulating and controlling variables to observe their effects and gather data. It is important to carefully plan and conduct the experiment to ensure reliable and valid results.

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Answer:

58.44 g/mol

Explanation:

In this problem, make sure to remember that volume is measured in mL, L or any other units of volume. Remember that g represents grams, and grams is a measure of mass.

However, independent of what mass or what volume we take, molar mass is known to be an intensive property. That is, molar mass doesn't depend on any external conditions or any measurements.

Molar mass solely depends on the chemical structure of a compound and is a constant number at any given conditions.

In this problem, we are given sodium chloride, NaCl. In order to find its molar mass, we need to refer to the periodic table, find the atomic masses of Na and Cl and then add them up to have the molar mass of NaCl:

[tex]M_{NaCl} = M_{Na} + M_{Cl} = 22.99 g/mol + 35.453 g/mol = 58.44 g/mol[/tex]

Answer:

This is an example of Green design.

Explanation:

Green design can be described as a method in which any building project is made by minimizing the harmful effects of construction on humans and environment. Green design is a sustainable design which is better for the economy too. In a green design, eco- friendly materials are used for construction works.

In the scenario discussed in the question, an engineer is using bamboo as a building material due to its eco- friendly features. Hence, it is an example of green design.

Answer:

B

Explanation:

Using the ideal gas law equation PV = nRT, and by converting the temperature to Kelvin, the pressure of the ideal gas is calculated to be 11.08 atmospheres.

The question pertains to the calculation of the pressure of an ideal gas given a certain amount of moles, volume, and temperature. To find the pressure on the gas, we use the ideal gas law equation PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature in kelvins.

First, we convert the temperature from Celsius to Kelvin: T(K) = -3.000 "+ 273.15 = 270.15 K.

We then use the value for R when pressure is in atmospheres, which is 0.0821 L  imes atm/(K  imes mol). With the given volume of 10.00 liters and the amount of 5.000 moles, the calculation is as follows:

P = (nRT)/V

P = (5.000 mol  imes 0.0821 L  imes atm/(K  imes mol)  imes 270.15 K) / 10.00 L

P = 11.08 atm

Thus, the pressure on the gas is 11.08 atmospheres, which corresponds to option (c).

Answer:

[ Na+ ]sln = 0.136 M

Explanation:

∴ mol Na2SO4 = ( 0.01728 L)×(0.078 mol/L) = 1.348 E-3 mol Na2SO4

⇒ mol Na+ = (1.348 E-3 mol Na2SO4)×(2 mol Na+/mol Na2SO4)

⇒ mol Na+ = 2.696 E-3 mol

∴ mol NaCl = (0.01130 L)×(0.20 mol/L) = 2.26 E-3 mol NaCl

⇒ mol Na+ = (2.26 E-3 mol NaCl)×(mol Na+/mol NaCl) = 2.26 E-3 mol Na+

⇒ total moles Na+ = 2.696 E-3 mol + 2.26 E-3 mol = 4.956 E-3 mol Na+

∴  total V sln = 17.28 mL + 11.30 mL + 7.84 mL = 36.42 mL = 0.03642 L sln

⇒ [ Na+ ]sln = (4.956 E-3 mol)/(0.03642 L) = 0.136 M

Answer:

4 m/s²

Explanation:

F/m

20N/4kg=

a= 4 m/s²

Answer:

c

Explanation:

Answer:

The correct answer is option C) When the atom absorbs photons, energy can only be emitted at specific frequencies creating a characteristic atomic emission spectra.

Explanation:

Emission spectrometry is a spectroscopic technique that analyzes the wavelengths of photons emitted by atoms or molecules during their transition from an excited state to a lower energy state. Each element emits a characteristic set of discrete wavelengths based on its electronic structure.

That is, each atom is capable of emitting or absorbing electromagnetic radiation, although only at some frequencies that are characteristic of each of the different chemical elements. If a certain element is stimulated in its gas phase, its atoms emit radiation at certain frequencies of the visible, which constitute its emission spectrum.

Expressed in other words, when a substance radiates with electromagnetic radiation the electrons choose the radiation of this continuous spectrum to produce jumps at higher levels (excited state).

When an electron jumps from its fundamental state to higher energy levels (excited state) and falls back to lower energy levels, the emission of a photon of a defined wavelength occurs that appears as a specific line or line in the spectrum broadcast. Electromagnetic radiation from radiation after passing through the substance is missing a series of lines that correspond to electronic jumps from the fundamental state to the excited state. It is what is called an absorption spectrum.

In summary, because each atom is capable of emitting or absorbing electromagnetic radiation, although only at some frequencies that are characteristic of each of the different chemical elements, the correct answer is option C) When the atom absorbs photons, energy can only be emitted at specific frequencies creating a characteristic atomic emission spectra.

Answer:

The correct option is B) Tropical rain forest

Explanation:

The tropical rain forest biome acquires four main characteristics:

1: Increased amounts of rainfall in a year

2: high average temperatures

3: soil that is not enriched with nutrients

4: increased level of biodiversity.

Extreme levels of biodiversity can be seen in the tropical rain forest biome. Hence, due to increased biodiversity, this biome has multistory communities. This biome contains about 50% of the world's known animal and plant species.

Answer: B :)

Explanation:

Answer:

The number of chlorine atoms present in [tex]6.02 \times 10^{23}[/tex] units of gold III chloride is [tex]18.066 \times 10^{23}[/tex]

Explanation:

Formula of Gold (III) chloride: [tex]AuCl_{3}[/tex]

Avogadro Number : Number of particles present in one mole of a substance.

[tex]{N_{0}} =6.022 \times 10^{23}[/tex]

Using,

[tex]n(moles)=\frac{Given\ number\ of\ particles}{N_{0}}[/tex]

[tex]n =\frac{6.02\times 10^{23}}{6.022\times 10^{23}}[/tex]

= 1 mole(0.9999 , nearly equal to 1 )

The given Gold III chloride sample is 1 mole in amount.

[tex]6.022 \times 10^{23}[/tex]  = 1 mole of [tex]AuCl_{3}[/tex]

In this Sample,

1 mole of [tex]AuCl_{3}[/tex] will give = 3 mole of Chlorine atoms

1 mole of Cl contain = [tex]6.022 \times 10^{23}[/tex]

3 mole of Cl contain = [tex]6.022 \times 10^{23}\times 3[/tex]

3 mole of Cl contain =[tex]18.066 \times 10^{23}[/tex]

So,

The number of chlorine atoms present in [tex]6.02 \times 10^{23}[/tex] units of gold III chloride is [tex]18.066 \times 10^{23}[/tex]

Answer:

²³⁸₉₃Np  → Pu₉₄²³⁸ + ⁰₋₁e

Explanation:

²³⁸₉₃Np  → Pu₉₄²³⁸ + ⁰₋₁e

Beta radiations:

Beta radiations are result from the beta decay in which electron is ejected. The neutron inside of the nucleus converted into the proton an thus emit the electron which is called β particle.

The mass of beta particle is smaller than the alpha particles.

They can travel in air in few meter distance.

These radiations can penetrate into the human skin.

The sheet of aluminium is used to block the beta radiation

⁴₆C → ¹⁴₇N + ⁰₋₁e

The beta radiations are emitted in this reaction. The one electron is ejected and neutron is converted into proton.

Since the questions were asked so late, the only reason why I am answering this question is for the people who have the same question.

So, this question is asked like this:

Complete the following radioactive decay problem.

238 Np ⟶  0 e + ___  ___

93                -1        ___

The answer is:

238 Pu

94

238 Np ⟶  0 e + 238 Pu

93                -1        94

Answer:

They are found in various parts of the periodic table: the whole group of the noble gases (8A), as well as some elements of alkali metals (1A), groups 5A, 6A and 7A (halogens)

Explanation:

There are a total of 11 elements in the periodic table which are gases at room temperature and standard atmospheric pressure.

Considering the periodic table, there's first of all one prominent group, the noble gases, group 8A. The whole group contains gases, those are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn).

The remaining ones are also typically diatomic at room temperature. First of all, hydrogen (H) in group 1A. At room temperature, it exists as a diatomic gas, [tex]H_2[/tex].

We also have one diatomic gas in group 5A, this is nitrogen, [tex]N_2[/tex]. Another diatomic gas is found in group 6A, this is oxygen, [tex]O_2[/tex].

The final gases belong to the group of halogens, group 7A, those are also diatomic, fluorine ([tex]F_2[/tex]) and chlorine ([tex]Cl_2[/tex]).

Answer:

1)O

2)R

Explanation:

Edge

The given one is a redox reaction. The oxidation reaction is the change from HI to I₂ and the reduction reaction is the metallic reduction of gold from the + 3 state to zero state.

A redox reaction is a combination of both oxidation and reduction. Oxidation is the process of reacting with oxygen or loss of electrons. Whereas, reduction is the gain of one or more electrons.

In an oxidation reaction, the electron will be after the arrow and in reduction reaction the electron is gaining and it will be before the arrow in the chemical equation.

For the given reaction,

oxidation -

[tex]\rm Au^{3+} + 3e^{-} \rightarrow Au[/tex]

The reduction half reaction is written as:

[tex]\rm 2I^{-} \rightarrow I_{2} + 2e^{-}[/tex]

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Final answer:

At equilibrium, the forward reaction rate equals the reverse reaction rate, indicating a dynamic balance where the concentrations of reactants and products remain constant.So,option d. The forward reaction rate is equal to the reverse reaction rate is correct.

Explanation:

When a reaction is at equilibrium, the forward reaction rate is equal to the reverse reaction rate. This state is achieved when the rate of the forward reaction decreases and becomes constant while, simultaneously, the rate of the reverse reaction increases and becomes constant, reaching a point where both rates are equal. This equilibrium indicates that the concentrations of reactants and products remain constant over time, illustrating a dynamic balance between the forward and reverse processes.

Answer: 1.D

2. A

3. D

Explanation:

Explanation:

To calculate that you need to know the value of the Kps (constant of solubility) at 30°C of KBr in water.

When the product of the concentrations of both ions (Br- and K+) equals the Kps, the solution is saturated.

Given the disociation of the salt in water:

[tex]KBr \longrightarrow K^+ + Br^-[/tex]

The concentration of both ions are equal (1:1 ratio) and the same as the concentration of KBr added.

The Kps:

[tex]Kps=[K^+][Br^-][/tex]

[tex][KBr]=(Kps)^{1/2}[/tex]

[KBr] are moles of the salt per litre of water

Assuming a density of water of 1 g/cm3, 100 g are 0.1 litre

To calculate the mass:

[tex]m=[KBr]*M*0.1 litre[/tex]

where M is the molecular weight of the salt.

[tex]65 \text{ grams of KBr}[/tex] is needed to make a saturated solution in 100g of water at 30C

To determine the amount of potassium bromide (KBr) needed to make a saturated solution in 100 grams of water at 30°C, one must refer to the solubility curve or table for KBr. The solubility curve provides the maximum amount of solute (in this case, KBr) that can be dissolved in a given amount of solvent (water) at a specific temperature.

At 30°C, the solubility of KBr in water is approximately 65 grams per 100 grams of water. This means that 65 grams of KBr can be dissolved in 100 grams of water to create a saturated solution at this temperature.

Therefore, the answer is: [tex]\[\boxed{65 \text{ grams of KBr}}\][/tex]

 To make a saturated solution of KBr in 100 grams of water at 30°C, one would need to dissolve 65 grams of KBr in 100 grams of water. If more than 65 grams of KBr were added, the excess would not dissolve, and the solution would still be saturated. If less than 65 grams were used, the solution would not be saturated unless the solubility decreases due to some other factor, such as the presence of a common ion or a change in temperature.

The answer is: [tex]65 \text{ grams of KBr}.[/tex]

Answer : The correct option is, (C) 2-octene

Explanation :

Structural formula or bond-line formula : In the structural formula, the bonding and type of bonds which holds the atoms in molecule together are shown.

In bond-line formula, the lines are used between the bonded atoms and the atoms are also shown.

The basic rules for naming of organic compounds are :

First select the longest possible carbon chain.

For the number of carbon atom, we add prefix as 'meth' for 1, 'eth' for 2, 'prop' for 3, 'but' for 4, 'pent' for 5, 'hex' for 6, 'sept' for 7, 'oct' for 8, 'nona' for 9 and 'deca' for 10.

A suffix '-ane' is added at the end of the name of alkane.

If two of more similar alkyl groups are present, then the words 'di', 'tri' 'tetra' and so on are used to specify the number of times these alkyl groups appear in the chain.

In the given hydrocarbon, the longest possible carbon chain number is 8 that means we add prefix 'oct' and suffix '-ene' for double bond. So, the name of given molecule will be, 2-octene.

Hence, the name of the given molecule is, 2-octene.

Answer:

¹⁴₆C → ¹⁴₇N + ⁰₋₁e

Explanation:

Beta radiations:

Beta radiations are result from the beta decay in which electron is ejected. The neutron inside of the nucleus converted into the proton an thus emit the electron which is called β particle.

The mass of beta particle is smaller than the alpha particles.

They can travel in air in few meter distance.

These radiations can penetrate into the human skin.

The sheet of aluminium is used to block the beta radiation

⁴₆C → ¹⁴₇N + ⁰₋₁e

The beta radiations are emitted in this reaction. The one electron is ejected and neutron is converted into proton.

Answer: 14N7 + 1n0 = 14C6 + 1H1

Explanation: The question shows how atoms are being represented by the number of proton and the number of electron.

By simply taking mass balance for the left and right hand sides, that is:

14N+1n =?C+ 1H

?C = 15-1 =14

Also,

N7+n0 = C? + H1

C? = 7+0-1

C? =6

Hence,

?C? = 14C6

Answer:

Ex1 = 4.3 moles

Explanation:

for Ex 1

 ** Number of mole = Mass (g) / Molecular weight ' Mw'  (g/mole)

for a = NaCl , first you must be calculate Mw = look to periodic table

Atomic weight for Na is 22.9 = 23 g and for Cl is 35.45 = 35 g

so Mw for NaCl = 23+35 = 58 g/mole

so Number of Moles for NaCl 250 g is

Number of Moles = 250 / 58 = 4.3 moles

do same for others ...

good luck ..

Answer:

Ex1. a) n NaCl = 4.277 mol NaCl

b) n KNO2 = 2.938 mol KNO2

c) n H2O2 = 7.349 mol H2O2

d) n KHSO3 = 2.080 mol KHSO3

Ex2. a) 2.31 E22 particles contained in 1.5 g K

b) 1.77 E22 particles contained in 0.470 g O

c) 2.332 E21 particles contained in 0.555 g AgCl

Ex3. molecules C2H5OH = 2.065 E24 molecules contained in 200 mL

Explanation:

Ex1.   n = mass (m) / molecular weight (Mw)

a) Mw NaCl = 22.989 + 35.453 = 58.442 g/mol

⇒ n NaCl = (250 g NaCl)/(58.442 g/mol) = 4.277 mol NaCl

b) Mw KNO2 = 39.0983 + 14.0067 + (2)15.9994 = 85.104 g/mol

⇒ n KNO2 = (250 g KNO2)/(85.104 g/mol) = 2.938 mol KNO2

c) Mw H2O2 = (2)(1.00794) + (2)15.9994 = 34.015 g/mol

⇒ n H2O2 = (250 g H2O)/(34.015 g/mol) = 7.349 mol H2O

d) Mw KHSO3 = 39.0983 + 1.00794 + 32.065 + 15.9994(3) = 120.169 g/mol

⇒ n KHSO3 = (250 g KHSO3)/(120.169 g/mol) = 2.080 mol KHSO3

Ex2.  n =  (m) / (Mw)

∴ 1 mol ≡ 6.022 E 23 particles

a) Mw K = 39.0983 g/mol

⇒  K = (1.5 g K)×(mol/39.0983 g K)×(6.022 E23 part/mol) = 2.31 E22 particles

b) Mw O = 15.9994 g/mol

⇒ O = (0.470 g O)×(mol/15.9994 g O)×(6.022 E23 part/mol) = 1.77 E22 part

c) Mw AgCl = 107.8682 + 35.453 = 143.32 g/mol AgCl

⇒ AgCl = (0.555 g)×(mol/143.32 g)×(6.022 E23 part/mol) = 2.332 E21 part.

Ex3. ethyl alcohol ( C2H5OH)

∴ δ C2H5OH = 0.79 g/mL

∴ V = 200 mL

⇒ molecules C2H5OH = ?

∴ Mw C2H5OH = (2)12.0107 + (5)1.00794 + 15.9994 + 1.00794 = 46.068 g/mol

⇒ molecules C2H5OH = (200 mL)×(0.79 g/mL)×(mol/46.068 g)×(6.022 E23 molecules/mol)

⇒ molecules C2H5OH = 2.065 E24 molecules C2H5OH

Answer: Interphase

Explanation: This is the stage in mitosis  where the cell grows, and DNA is being replicated. This happens during the Synthesis Phase of Interphase.

Answer: C interphase

Explanation:

Answer:

Work done = 600 J

Power used = 60 W

Explanation:

Given:

Force acting on the box is, [tex]F=20\ N[/tex]

Displacement of the box is, [tex]S=30\ m[/tex]

Time taken for the work, [tex]t=10\ s[/tex]

Now, we know that, work is said to be done by a force only when there is displacement caused by the force in its direction.

Here, the force acting on the box causes a displacement of 30 m in its direction. So, work done is equal to the product of force and displacement caused.

Therefore, work done on the box is given as:

[tex]Work=Force\times Displacement\\Work=F\times S\\Work=(20\ N)\times (30\ m)\\Work=600\ J[/tex]

Therefore, the work done is 600 J.

Now, we know that, power is given as work done per unit time.

So, power used is given as:

[tex]Power=\frac{Work}{Time}\\\\Power=\frac{600\ J}{10\ s}\\\\Power=60\ W[/tex]

Therefore, the power used is 60 W.

Answer:

The periodic table is a table representing all the elements found in nature.

Following are the limitations of the modern periodic table:

Answer:

Chemical energy!

Answer:

CHEMICAL ENERGY is your correct answer for this question

Explanation:

The dot structure for magnesium illustrates it losing its two outermost electrons when forming compounds like MgO, indicating its tendency to achieve stability. Magnesium can participate in more complex bonding geometries, such as 4-coordinate (tetrahedral), but in the simple formation of magnesium oxide, the focus is on the ionic bond and electron transfer.

The question asks for the dot structure for magnesium, focusing specifically on its bonding and coordination number in chemical compounds. Magnesium, with an atomic number of 12, has its electrons arranged in a [Ne]3s² configuration. This means magnesium has two electrons in its outermost shell that it tends to lose to achieve a stable electronic arrangement, resembling the nearest noble gas, neon. When forming ionic compounds like magnesium oxide (MgO), magnesium donates its two outermost electrons to oxygen, resulting in a structure where magnesium has no dots around its symbol, indicating it has lost its valence electrons.

Magnesium's tendency to form compounds with specific geometries, either 4-coordinate (tetrahedral) or 6-coordinate (octahedral), highlights its versatility in chemical bonding. However, in the simpler case of forming ionic bonds, as in MgO, the focus is primarily on the transfer of electrons rather than the arrangement in complex geometries. The transformation into MgO exemplifies this process, underscoring the ionic character of the bond formed between magnesium and oxygen, a key concept in understanding magnesium's chemical behavior.

Answer:

The percent yield is 42.52%.

Explanation:

Theoretical yield of beryllium chloride = 12.7 g

Actual yield of the beryllium chloride = 5.4 g

The formula used for the percent yield will be :

[tex]\text{Percent yield}=\frac{\text{Actual yield}}{\text{Theoretical yield}}\times 100[/tex]

Now put all the given values in this formula, we get:

[tex]\%(yield)=\frac{5.4 g}{12.7 g}\times 100=42.52\%[/tex]

The percent yield is 42.52%.

Answer:

[tex]2s^2 2p^2[/tex]

Explanation:

Group 4A contains a total of 4 electrons for each atom in their valence shell. Filling the orbital diagram, let's say, for carbon, notice that when we start with period 2, we have two elements in the s-block, that is, lithium and beryllium. They correspond to the two s electrons that belong to the valence shell of carbon.

Moving on, we have boron and carbon, the remaining 2 electrons. Now, starting with boron, we're in the p-block.

That said, looking at the second period, the electron configuration for the valence shell of a group 4A element would be:

[tex]2s^2 2p^2[/tex]

｡☆✼★ ━━━━━━━━━━━━━━  ☾

It's an atom with the same number of protons but a different number of neutrons and thus, a different mass number.

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Explanation: Every atom/element is defined by its protons so if it has 1 atom it's hydrogen no matter what, if it has 2 protons it's helium no matter what and so on. If you know the number or protons, you know the element.

You can change the number of neutrons in the nucleus and you'll get isotopes. So atoms that have different numbers of neutrons are isotopes of each other. However, the element is the same but one is going to be a little bit heavier or lighter than another.

So, isotopes are different versions of an element.

Answer:

15 g

Explanation:

Data given:

amount of  HF  = 153 mL  2.5 M HF

amount of Ca(OH)₂ = Excess

grams of CaF₂ = ?

Reaction Given:

                2HF + Ca(OH)₂ ------→ 2H₂O + CaF₂

Solution:

First we have to find number of moles of HF in 153 mL of 2.5 M HF

For this we will use following formula

               Molarity = moles of solute / liter of solution

Rearrange above equation

               moles of solute =  Molarity x liter of solution . . . . . (1)

Put values in above equation (1)

               moles of solute =  2.5 x 1 L

              moles of solute =  2.5

So,

we come to know that there are 2.5 moles of solute (HF) in 1 L of solution

Now how many moles of solute will be present in 153 ml of solution

Convert 153 mL to Liter

1000 mL = 1 L

153 mL = 153/1000 = 0.153 L

Apply Unity Formula

                       2.5 moles HF ≅ 1 L solution

                        X moles of HF ≅ 0.153 L solution

              moles of HF = 2.5 moles x 0.153 mL solution / 1 L solution

              moles of HF =  0.383 moles

Now Look at the reaction:

                     2HF + Ca(OH)₂ ------→ 2H₂O + CaF₂

                    2 mol                                          1 mol

From the reaction we come to know that 2 moles of HF gives 1 mole of CaF₂ then how many moles of CaF₂  will be produced from o.383 moles of HF

Apply Unity Formula

                       2 moles HF ≅ 1 mole of CaF₂

                       0.383 moles of HF ≅ X moles of CaF₂

              moles of CaF₂  = 0.383 moles x 1 mole / 2 mol

              moles of CaF₂ =  0.192 moles

Now we will find mass of 0.192 moles of  CaF₂

Formula will be used

          mass in grams = no. of moles x molar mass . . . . . . . (2)

molar mass of CaF₂ = 40 + 2(19)

molar mass of CaF₂ = 40 + 38 =  78 g/mol

Put values in eq. 2

        mass in grams = 0.192 x 78 g/mol

        mass in grams = 14.976 g

rounding the value

          mass in grams = 15 g

So,153 mL of 2.5 M HF is reacted with an excess of Ca(OH)₂ will produce 15 g of CaF₂.