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Posted in Chemistry

Which of the following statements about ionization energy is true? A. In a period, elements farther to the right generally have lower ionization energies than elements on the left. B. Elements toward the bottom of a group periodic table generally have higher ionization energies than elements at the top of the group. C. Ionization energy is the amount of energy used to add an electron to an atom. D. Potassium has a lower ionization energy than sodium.


Ionization energy is the energy needed to remove an electron from an atom's valence shell. It increases from left to right, across the period, and decreases from top of bottom, along the group. With this info, you can figure it out. Hope this helps. Have a nice day.

Related Questions

Posted in Chemistry

Which statement best explains why a carbon atom can bond easily with other atoms? It is an ion. It is an organic element. It has four valence electrons. It forms hydrogen bonds.

Based on the definition of a carbon atom, the statement that best explains why a carbon atom can bond easily with other atoms because it  has four valence electrons. So the answer would be the third option. Hope this answers your question.

Posted in Chemistry

Sulfur and fluorine react in a combination reaction to produce sulfur hexafluoride: S(g) + 3F2(g) ->SF6(g) If 50 g S is allowed to react as completely as possible with 105.0g F2(g), what mass of the excess reactant is left.

The balanced chemical reaction is:

S(g) + 3F2(g) ->SF6(g)

We are given the amount of the reactants to be used in the reaction. We use these as the starting values for the calculations. We calculate as follows:

50 g S ( 1 mol / 32.066 g ) = 1.56 mol S
105 g F2 ( 1 mol / 38.00 g ) = 2.76 mol F2

The limiting reactant would be F2 since it will be consumed completely in the reaction. The excess reactant would be S. 

Mass of excess = 1.56 mol - 2.76(1/3) = 0.64 mol S excess

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You carefully weigh out 14.00 g of CaCO3 powder and add it to 56.70 g of HCl solution. You notice bubbles as a reaction takes place. You then weigh the resulting solution and find that it has a mass of 64.96 g . The relevant equation is CaCO3(s)+2HCl(aq)→H2O(l)+CO2(g)+CaCl2(aq) Assuming no other reactions take place, what mass of CO2 was produced in this reaction?

Answer : The mass of CO_2 produced will be, 6.16 grams.

Explanation : Given,

Mass of CaCO_3 = 14 g

Mass of HCl = 56.70 g

Molar mass of CaCO_3 = 100 g/mole

Molar mass of HCl = 36.5 g/mole

Molar mass of CO_2 = 44 g/mole

First we have to calculate the moles of CaCO_3 and HCl.

\text{Moles of }CaCO_3=\frac{\text{Mass of }CaCO_3}{\text{Molar mass of }CaCO_3}=\frac{14g}{100g/mole}=0.14moles

\text{Moles of }HCl=\frac{\text{Mass of }HCl}{\text{Molar mass of }HCl}=\frac{56.70g}{36.5g/mole}=1.55moles

Now we have to calculate the limiting and excess reagent.

The balanced chemical reaction is,

CaCO_3(s)+2HCl(aq)\rightarrow CO_2(g)+H_2O(l)+CaCl_2(aq)

From the balanced reaction we conclude that

As, 1 moles of CaCO_3 react with 2 mole of HCl

So, 0.14 moles of CaCO_3 react with 0.14\times 2=0.28 moles of HCl

From this we conclude that, HCl is an excess reagent because the given moles are greater than the required moles and CaCO_3 is a limiting reagent and it limits the formation of product.

Now we have to calculate the moles of CO_2.

As, 1 moles of CaCO_3 react to give 1 moles of CO_2

So, 0.14 moles of CaCO_3 react to give 0.14 moles of CO_2

Now we have to calculate the mass of CO_2.

\text{Mass of }CO_2=\text{Moles of }CO_2\times \text{Molar mass of }CO_2

\text{Mass of }CO_2=(0.14mole)\times (44g/mole)=6.16g

Therefore, the mass of CO_2 produced will be, 6.16 grams.

Posted in Chemistry

Which of the following are most likely to form a metallic bond? several gold atoms copper and chlorine magnesium and chlorine several chlorine atoms

I think the correct answer from the choices listed above is the first option. It would be several gold atoms that will form a metallic bond. It is the most logical choice since it is a metal while the others are nonmetal and a combination of metal and nonmetal. Hope this answers the question. Have a nice day.

Posted in Chemistry

One of the isotopes of sulfur is represented as sulfur-35 or S-35. What does the number 35 signify?

One of the isotopes of sulfur is represented as sulfur-35 or S-35. The number 35 represents the mass number of the isotope. The mass number (A), also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus.

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Which of the following is a possible set of quantum numbers for an electron n, l, m subscript l, m subscript ? (1, 0, 0, +1) (2, 2, 1, +½) (4, -3, 0, -½) (3, 2, 1, -½)

So based on the given sets of quantum numbers above for an electron n,l,m subscript l, m subscript, the correct answer for this would be the last option. So the possible set of quantum numbers for an electron n, l, m subscript l, m subscript would be this: (3, 2, 1, -½). Hope this answers the question. 

Posted in Chemistry

Monel metal is a corrosion-resistant copper-nickel alloy used in the electronics industry. A particular alloy with a density of 8.80 g/cm3 and containing 0.073% Si by mass is used to make a rectangular plate that is 15.0 cm long, 12.5 cm wide, and 2.50mm thick and has a 2.50-cm-diameter hole drilled through its center such that the height of the hole is 2.50mm . The silicon in the plate is a mixture of naturally occurring isotopes. One of the those isotopes is silicon-30, which has an atomic mass of 29.97376 amu and a percent natural abundance of 3.10% How many silicon-30 atoms are found in this plate? Express your answer numerically using two significant figures.

Answer is: there are 1.82·10²⁰ silicon-30 atoms.

V₁(alloy) = 15 cm · 12.5 cm · 0.25 cm.

V₁(alloy) = 46.875 cm³; volume of the alloy without hole.

V(hole) = 0.25 cm · (1.25 cm)² · 3.14.

V(hole) = 1.23 cm³

V₂(alloy) = 46.875 cm³ - 1.23 cm³.

V₂(alloy) = 45.65 cm³; volume of the alloy with hole.

m(alloy) = V₂(alloy) · d(alloy).

m(alloy) = 45.65 cm³ · 8.80 g/cm³.

m(alloy) = 401.7 g; mass of the alloy.

ω(Si) = 0.073% ÷ 100%.

ω(Si) = 0.00073.

m(Si) = ω(Si) · m(alloy).

m(Si) = 0.00073 · 401.7 g.

m(Si) = 0.293 g; mass of silicon it the alloy.

m(Si-30) = m(Si) · ω(Si-30).

m(Si-30) = 0.293 g · 0.031.

m(Si-30) = 0.0091 g; mass of the silicon-30.

n(Si-30) = m(Si-30) ÷ M(Si-30).

n(Si-30) = 0.0091 g ÷ 29.97376 g/mol.

n(Si-30) = 0.000303 mol; amount of the silicon-30.

N(Si-30) = n(Si-30) · Na (Avogadro constant).

N(Si-30) = 0.000303 mol · 6.022·10²³ 1/mol.

N(Si-30) = 1.824·10²⁰.

Posted in Chemistry

Draw a complete Lewis structure for the conjugate acid of nitromethane that shows all bonds, unshared electron pairs, and minimized formal charges, where appropriate.

Answer:

Lewis structures are shown below

Explanation:

  • In Lewis structure of nitromethane, a negative charge is present on oxygen atom in nitro group.
  • Hence this oxygen atom acts as a basic center preferably.
  • Therefore conjugate acid of nitromethane should be drawn by adding a hydrogen atom with this oxygen atom.
  • Lewis structure of nitromethane as well as it's conjugate acid has been shown below including all the lone pairs and formal charges

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A teacher makes the following statement. “Gasoline boils at a relatively low temperature (about 150°C). The kerosene is removed at around 200°C, followed by diesel oil at 300°C and fuel oil at around 370°C.” What topic is the teacher most likely talking about? a. distillation of a mixture b. filtration of a pure substance c.evaporation of a mixture d. sorting of a pure substance

Answer:

The correct answer is option a.

Explanation:

According the question, boiling points of different liquids are discussed which means that if we take all these liquids in single mixture we can separate them from each other on the basis of their difference in boiling point. And the technique which employs this principle is distillation process.

Hence, we can say teacher is most likely talking about distillation of a mixture of oils.

Distillation is a process which is used to separate mixture of different liquids from each other. In this process, during the course of boiling of mixture liquid compound with lower boiling points vaporizes first leaving behind the liquid with higher boiling point behind.

And vapors of boiled liquid are condensed down in a separate container for the collection.

Posted in Chemistry

Which of the following ions would represent the ion of an element from Group 2A? A. X2- B. Y3+ C. Z+ D. A2+

An element belongs to particular group is related to the number of electrons present in the outer shell of the atoms. In given case, group is 2, therefore, number of valence electrons is 2 implies it has ability to lose two electrons to get +2 charge.

A\rightarrow A^{+2}+2e^{-}

Therefore, ion formed after removal of two electrons is A^{2+}.

Hence, option (D) is the correct answer.






Posted in Chemistry

What is the mass of 5.05×1021 platinum atoms?

Answer: 1.6 gram

Explanation:

According to avogadro's law, 1 mole of every substance occupies 22.4 L at STP and contains avogadro's number 6.023\times 10^{23} of particles.

To calculate the moles, we use the equation:

\text{Number of moles}=\frac{\text{Given atoms}}{\text {Avogadro's Number}}

\text{Number of moles of water}=\frac{5.05\times 10^{21}}{6.023\times 10^{23}}=8.4\times 10^{-3}moles

1 mole of Platinum Pt weighs 195 g

8.4\times 10^{-3}moles  of Platinum Pt weigh =\frac{195}{1}\times 8.4\times 10^{-3}=1.6g

Thus mass of 5.05\times 10^{21} platinum atoms is 1.6 gram.

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Posted in Chemistry

Which statement about van der Waals forces is true?

Van der Waals forces' is a general term used to define the attraction of intermolecular forces between molecules. They  are the residual attractive or repulsive forces between molecules or atomic groups that do not arise from a covalent bond, or ionic bonds. Hope this answers the question.

Posted in Chemistry

Identify the group of elements that corresponds to the following generalized electron configuration: [noble gas]ns 2 (n−1)d 2

For the answer to the question above, I think you are referring to the group of four elements. The Titanium, Zirconium, Hafnium and lastly the Rutherfordium are the group of elements that corresponds to the configuration you are asking.
I hope my answer helped you

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Which of these is a property of a substance that is composed of atoms that are held together by ionic bonds? It can be shaped into wires. It has a low melting point. It conducts electricity when in solid form. It conducts electricity when it is dissolved in water.

Answer: Option (D) is the correct answer.

Explanation:

A ionic compound will have opposite charges on the 2 atoms attached to each other.

When ionic compound is in solid state then atoms will be more closer to each other and also due to the opposite charges the molecules will have strong force of attraction between them.

In order to conduct electricity, free movement of ions is required. So, a solid with ionic bonds is not able to conduct electricity as molecules or ions are closely held together.

Whereas when a substance that is composed of atoms that are held together by ionic bonds is dissolved in water then its ions will start to move freely from one point to another. Thus, this solution will be able to conduct electricity.

Thus, we can conclude that out of the given options, conducts electricity when it is dissolved in water displays a property of a substance that is composed of atoms that are held together by ionic bonds.

Posted in Chemistry

A machine is a device that creates energy

FALSE!
We can't create or destroy energy. Machine is a device that converts one form of energy into another.

Hope this helps!

Posted in Chemistry

Which grouping has the least complex body plan? If you were on a research expedition in the kingdom of Tonga, a coral atoll in the South Pacific, would you find these organisms?

YES, I WOULD FIND THOSE ORGANISMS.

The Kingdom of Tonga is a Polynesian Archipelago in Oceania consisting of 176 islands. During a month long coral reef research mission in Tonga, the Foundation focused on islands in the Ha’aipi group, Vava’u and Niuatoputapu. Haʻapai, directly west of the Tonga trench in the central part of Tonga, is made up of 51 volcanic islands and includes Kao, the highest point in the kingdom (1,046 m). Vavaʻu has one large island and 40 smaller ones, and includes the second largest city, a large harbor.  The north side of the main island is lined by 200 m high cliffs and extensive open network of fjord-like channels that stretch inland on the north side. Nearly 300 km north of Vavaʻu, close to the border of Samoa is Niuatoputapu, a sparsely inhabited (population 150)  eroded remnant of a volcano surrounded by a large uplifted reef. This island was badly damaged by a tsunami following a submarine earthquake off Samoa in 2009.

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Posted in Chemistry

Given the data in the accompanying table, what is the reaction order for B? A) zero B) first C) second D) third

Answer: The order with respect to B is

Explanation: Rate law says that rate of a reaction is directly proportional to the concentration of the reactants each raised to a stoichiometric coefficient determined experimentally called as order.

Rate=k[A]^x[B]^y

k= rate constant

x = order with respect to A

y = order with respect to B

n = x+y = Total order

a) From trial 1: 20=k[0.20]^x[0.10]^y    (1)

From trial 2: 40=k[0.20]^x[0.20]^y    (2)

Dividing 2 by 1 :\frac{40}{20}=\frac{k[0.20]^x[0.20]^y}{k[0.20]^x[0.10]^y}

2=2^y,2^1=2^y therefore y=1.

Thus order with respect to B is 1.

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Posted in Chemistry

An atom has no overall charg if it contains equal number of

Protons (positively charged) and electrons (negatively charged). They would cancel each others charges out thus causing the atom to have a neutral or no charge. 

Posted in Chemistry

How many electrons are in O2.

Number of electron in O = 8
So, in O2 it would be: 8 * 2 = 16

So, your final answer is 16

Hope this helps!

Posted in Chemistry

Which statement best relates the strength and concentration of a base? At high enough concentrations, a weak base becomes strong. Even at low concentrations, a strong base is strong. A weak base always has a low concentration. The stronger the base, the higher its concentration.

Answer: Option (b) is the correct answer.

Explanation:

When there are more number of hydroxide ions in a solution then there will be high concentration of OH^{-} or hydroxide ions. As a result, more will be the strength of base in that particular solution.

A base is strong when it readily dissociate into its ions in the solution. When a base is strong, then it does not matter at what concentration it is dissolved in the solution because despite of its low concentration it will remain a strong base.

Thus, we can conclude that out of the given options, the statement even at low concentrations, a strong base is strong best relates the strength and concentration of a base.


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Posted in Chemistry

Which type of atom has the strongest attraction for electrons in bond formation? barium (Ba) chlorine (Cl) iodine (I) strontium (Sr)

Answer: Chlorine has the strongest attraction for electrons in bond formation.

Explanation:

Chlorine is highly electronegative as compared to iodine and has high electron gain enthalpy. So, it will readily accept an electron in order to complete its octet. The electronegativity decreases down the group from Cl to I, and hence the tendency to gain an electron decreases.

In case of Barium, and Strontium there are completely filled sub shells and therefore the tendency to gain an electron is the least.  

Thus, it can be concluded that chlorine has the strongest attraction for electrons in bond formation.

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Which of the following statements about the use of nuclear energy is true? a. Nuclear energy cannot be used safely. b. Nuclear fusion has no known useful applications. c. Nuclear fission is currently more useful for producing energy than nuclear fusion. d. Nuclear fusion has fewer safety risks than nuclear fission.

Answer: The correct answer is "Nuclear energy cannot be used safely".

Explanation:

There are two types of nuclear reactions: Nuclear fission and Nuclear fusion.

Nuclear fission: The nuclear energy is originated from the splitting of uranium atom. Uranium is a radioactive material.

Nuclear reactor controls the release of energy.

The by product of the nuclear generation is the radioactive waste in the nuclear power plant.

The radioactive material emits harmful radiation. If there is any leakage in the power plant. Then, it would lead to hazard. It would harmful for the health of the employees who are working there.

Therefore, the correct option is (a).

Posted in Chemistry

Carbon-14 has a half-life of 5730 years. In a plant fossil, you find that the 14C has decayed to 1/4.00 of the original amount. How long ago was this plant alive?

Answer:

The plant was alive for 1155 years

Explanation:

Any radioactive decay process follows the exponential law which is mathematically expressed as:

N(t)= N(0)e^{-kt}------(1)

where N(0) = initial amount of the radioactive material

N(t) = amount at time t

k = decay constant

The decay constant is in turn related to the half-life t1/2

k = \frac{0.693}{t1/2}----(2)

It is given that t1/2 of 14C = 5730yrs. Therefore:

k = \frac{0.693}{5730}=1.21*10^{-4}yr-1

In addition it is mentioned that:

N(t) = 1/4*N(0)

substituting this in equation (1) gives:

1/4*N(0)= N(0)e^{-1.21*10^{-4}t}

t = 1155 years

Posted in Chemistry

Which of the following statements correctly describes boyle's law

In the said law, the volume of a gas varies inversely with pressure. Boyle's law is one of the gas laws we have. According to this law, at a fixed amount of an ideal gas which is at constant temperature, the pressure and volume are inversely proportional with each other. The variables are volume and pressure.

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