which is an example of an element?
A)Salt (NaCl)
B)Water (H2O)
C) Silver (Ag)
D) Electron (electron (e-)
Which number determines how the periodic table is arranged?
●1. What is the density of 2.0 g of a substance that has a volume of 5.0 mL?
The density of 2.0 g of a substance that has a volume of 5.0 mL is 0.4 g/ml.
What is density ?The mass of a substance per unit of volume is its density. Density is most frequently represented by the symbol, however the Latin letter D may also be used. Density is calculated mathematically by dividing mass by volume.
How much "stuff" is contained in a specific quantity of space is determined by its density. For instance, a block of the harder, lighter element gold (Au) will be denser than a block of the heavier element lead (Pb) (Au). Styrofoam blocks are less dense than bricks. Mass per unit volume serves as its definition.
Because it enables us to predict which compounds will float and which will sink in a liquid, density is a crucial notion.
Density = Mass / Volume
Density = 2.0g / 5.0ml
Density = 0.4 g/ml
Thus, The density of 2.0 g of a substance that has a volume of 5.0 mL is 0.4 g/ml.
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Particles in a plasma experience collisions than particles in a solid. Based on their state of matter alone, is it easier to speak of the shape of the Sun or the Moon? Two unknown substances are in identical beakers. One is a solid and the other is a plasma. If you were given a scale to allow you to obtain the mass of the substance, and had to guess based on mass alone, you would say that the plasma is in the beaker.
Particles in a plasma experience more collisions than particles in a solid.
Based on their state of matter alone, is it easier to speak of the shape of the Sun or the Moon? moon
Two unknown substances are in identical beakers. One is a solid and the other is a plasma. If you were given a scale to allow you to obtain the mass of the substance, and had to guess based on mass alone, you would say that the plasma is in the lighter beaker.
Of protons neutrons and electrons, which of these can never change in atom during an ordinary chemical or physical change
The number of electron or proton of an atom can change depending on the chemical bond and the other chemical it is bonded with; an atom can either gain or lose electron. However, the number of neutrons of an atom can never change, this is the primary identity or signature of an atom.
Answer:
neutrons
In an ordinary chemical or physical change, the protons within an atom remain unchanged. They reside in the atom's nucleus and define the atom's identity. Chemical reactions mostly involve movement of electrons whilst protons remain constant.
Explanation:In the context of an ordinary chemical or physical change, the particle that remains unchanged within an atom is the proton. Protons, along with neutrons, reside within the nucleus of the atom, and are fundamental to an atom's identity. Each unique element is distinguished by its specific number of protons, known as the atomic number.
Chemical reactions, which are characterized by the rearrangement of atoms, primarily involve the movement of electrons, which constitute the outer part of an atom. Positive charges form when these electrons are lost. However, the number of protons remains constant throughout these changes.
An exception to this rule comes into play with certain nuclear reactions, such as radioactive decay, where the number of protons can change, leading to the formation of a different element. However, these are not considered 'ordinary' chemical or physical changes.
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Why should those investigating a crime scene minimize contamination and what are some ways that contamination is limited at a crime scene
Minimizing contamination at a crime scene is essential to preserve evidence integrity, mirroring the importance of cleanliness in laboratory settings. Strategies like restricting access, using PPE, documenting everything carefully, and proper evidence collection are critical in preventing contamination. These measures help maintain the crime scene's integrity, aiding in solving the crime effectively.
Explanation:Minimizing contamination at a crime scene is crucial to preserving the integrity of evidence, which is key to solving the crime effectively. Just as in a laboratory, where cleanliness and precise handling of materials are paramount to prevent cross-contamination and ensure accurate results, a crime scene requires stringent measures to avoid altering the scene or introducing foreign substances. This caution is pivotal because the evidence must reflect the event accurately without external influence, akin to preventing hazardous waste complications by avoiding spills rather than addressing them post-occurrence.
Several strategies help limit contamination at a crime scene, including:
Restricting access to the crime scene to essential personnel only to minimize the potential for contamination.Using personal protective equipment (PPE), such as gloves and shoe covers, to prevent investigators from leaving their own DNA or other trace evidence.Documenting everything meticulously before moving or touching anything. This can help ensure that the original condition of the scene is recorded and preserved.Employing proper evidence collection techniques, such as using clean tools and containers for each piece of evidence to prevent cross-contamination.Adhering to these practices helps maintain the crime scene's integrity, providing a clearer, uncontaminated narrative of events that enhances the chances of solving the crime and ensuring justice.
What is the mass of a light bulb
The mass of a light bulb varies depending on the type and size of the bulb and is not given by its power rating. The power ratings, such as 60 W or 100 W, pertain to energy consumption, not to mass. To find the mass, you would need to physically weigh the bulb.
Explanation:Mass of a Light Bulb
The question does not explicitly specify the mass of a light bulb. However, as a physics concept, when discussing light bulbs, we often refer to their energy consumption and power ratings rather than their physical mass. A light bulb's power rating, such as 60 watts (W) or 100 watts (W), indicates how much electrical energy it uses per unit of time. The mass of a light bulb can vary based on the type and size of the bulb.
When we're examining a bulb's energy usage, we might ask how much energy a 100 W light bulb uses or compare the resistance and current in light bulbs of different wattages. The resistance of a filament in a bulb determines the amount of energy converted into heat and light. A higher-wattage bulb will usually be hotter and brighter as it converts more electrical energy compared to a lower-wattage bulb.
For the mass of a specific light bulb, you would typically need to weigh it using a scale, as the mass is not directly related to its power consumption or electrical characteristics.
The conjugate acid of a particular halide has a pka = 3. a student wants to use this halide in a substitution reaction thinking it will have a good leaving group. can this student use this halide in a substitution reaction?
Since the leaving ability of the halide ions increasees as the basicity of the halide decreases.
If the basicity of the halide decreases as the its conjugate acid is strong.
Since the pKa value of conjuage acid of haldie is 3, it is a weak acid. So, it halide is not a good leaving group.
Therefore the answer is No, because a good leaving group is the conjugate base of a strong acid. The halide not acidic enough to be a good leaving group.
Reaction of (r)-2-chloro-4-methylhexane with excess nai in acetone gives racemic 2-iodo-4-methylhexane. what is the explanation that best describes this transformation?
I believe this question has the following five choices to choose from:
>an SN2 reaction has occurred with inversion of configuration
>racemization followed by an S N 2 attack
>an SN1 reaction has taken over resulting in inversion of configuration
>an SN1 reaction has occurred due to carbocation formation
>an SN1 reaction followed by an S N 2 “backside” attack
The correct answer is:
an SN1 reaction has occurred due to carbocation formation
The correct option is 3. The correct explanation for the transformation described is: 3. An SN¹ reaction followed by an SN² "backside" attack.
- The reaction involves (R)-2-chloro-4-methylhexane reacting with excess NaI in acetone.
- NaI in acetone is a typical condition for an SN¹ (substitution nucleophilic unimolecular) reaction.
- During the SN¹ reaction, the leaving group (chlorine) is replaced by the nucleophile (iodide).
- This SN¹ reaction typically results in inversion of configuration at the carbon center due to the nucleophile attacking from the opposite side of the leaving group.
- Subsequently, an SN² (substitution nucleophilic bimolecular) reaction can occur, where the nucleophile attacks the carbon center again, leading to racemization (formation of both enantiomers) due to the nucleophile attacking from both sides of the planar intermediate formed after SN¹.
- The overall result is racemic 2-iodo-4-methylhexane, indicating that both (R)- and (S)-enantiomers are formed in equal amounts.
Therefore, option 3 best describes the sequence of reactions leading to the formation of racemic 2-iodo-4-methylhexane.
The complete question is- Reaction of (R)-2-chloro-4-methylhexane with excess NaI in acetone gives racemic 2-iodo-4-methylhexane. What is the explanation that best describes this transformation?
1. an SN¹ reaction has taken over resulting in inversion of configuration
2. an SN¹ reaction has occurred due to carbocation formation
3. an SN¹ reaction followed by an SN² "backside" attack
4. racemization followed by an SN² attack
5. an SN² reaction has occurred with inversion of configuration
What mass of co2 would be produced by the neutralization of 25.0 ml of 6.00m h2so4 using excess nahco3?
The complete balanced reaction is:
H2SO4 + 2NaHCO3 --> Na2SO4 + 2H2O + 2CO2
Then we calculate the number of moles of H2SO4:
moles H2SO4 = 0.025 L * 6 moles / L = 0.15 moles
From stoichiometry of the balanced equation:
moles CO2 = 0.15 moles H2SO4 * (2 moles CO2 / 1 mole H2SO4) = 0.30 moles
The molar mass of CO2 is 44 g / mol, therefore the mass produced is:
mass CO2 = 0.30 moles * (44 g/ mol) = 13.2 g CO2
Answer:
13.2 g CO2
If an element has an atomic number of 11 and a mass number of 23, how many protons, neutrons, and electrons does it have
Before investigating the scene, the technician must dilute the luminol solution to a concentration of 4.00×10−2 M . The diluted solution is then placed in a spray bottle for application on the desired surfaces. How many moles of luminol are present in 2.00 L of the diluted spray?
8 x 10⁻² moles of luminol are present in the 2.00L of the diluted spray.
The number of moles =? The molarity = (4.0 x 10⁻² M) Volume = 2LMolarity refers to the molar concentration of solution and expressed as the number of moles of solute in one liter of solution. In other words, it is the concentration of a solution in regards to the number of moles of the solute in one liter of solution.
Further ExplanationTo determine the Molarity of a solution, the moles of solute will be divided by the liters of solution. This can be expressed as:
Molarity = moles of solute / liters of solution
if you cross multiply, then you have:
N = M x V
Therefore, In the given question, the mole of luminol can be calculated using the Equation below:
N = M x V , where
N represents the number of moles M represents molarity V represents the Volume (liters of solution)If you substitute the Values, then you have:
n = (4.0 x 10⁻² M) (2 L)
n = 8 x 10⁻² moles
Thus, 8 x 10⁻² moles of luminol are present in the 2.00L of the diluted spray.
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Before investigating the scene, the technician must dilute the luminol solution to a concentration of 4.00×10−2 M https://brainly.com/question/5685664The forensic technician at a crime scene has just prepared a luminol stock solution by adding 19.0g of luminol into a total volume of 75.0mL of H2O https://brainly.com/question/2814870KEYWORDS:
luminoldiluted solutionmolaritymolesdiluted spraysolute per literThe temperature of a 500 ml sample of gas increases from 150 k to 300 k. what is the final volume of the sample of gas, if the pressure in the container is kept constant?
Can an enzyme make a nonspontaneous reaction occur spontaneously? why or why not? see section 8.3 ( page 180) .
What is a solution that contains a large amount of solute compared to solvent?
How many valence electrons are in a stable ion of a period 4 metal?
A stable ion of a period 4 metal typically has 2 valence electrons, but the specific number can vary depending on the element within the period.
How many valence electrons are in a stable ion of a period 4 metal?In a period 4 metal, the number of valence electrons can vary depending on the specific element. However, many period 4 metals, such as those in Group 2 (e.g., calcium, strontium) and Group 12 (e.g., zinc, cadmium), have 2 valence electrons because they are in the s-block of the periodic table. These metals typically form stable ions by losing these valence electrons to achieve a stable electron configuration.
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A homogeneous mixture has the same composition throughout.
a. True
b. False
How many degenerate orbitals are needed to contain six electrons with two of them unpaired?
In this case, we are dealing with the 2p orbitals. The 2p sublevel consists of three orbitals, so we need to draw all three orbitals even if one or more are unoccupied. According to Hund's rule, the sixth electron enters the second of those p orbitals, with the same spin as the fifth electron.
Explanation:The question is asking how many degenerate orbitals are needed to contain six electrons with two of them unpaired. In this case, we are dealing with the 2p orbitals. The 2p sublevel consists of three orbitals, so we need to draw all three orbitals even if one or more are unoccupied. According to Hund's rule, the sixth electron enters the second of those p orbitals, with the same spin as the fifth electron.
N which group do all atoms have eight valence electrons in the ground state?
According to the electronic configuration, group 18 elements have eight valence electrons in the ground state.
What is electronic configuration?Electronic configuration is defined as the distribution of electrons which are present in an atom or molecule in atomic or molecular orbitals.It describes how each electron moves independently in an orbital.
Knowledge of electronic configuration is necessary for understanding the structure of periodic table.It helps in understanding the chemical properties of elements.
Elements undergo chemical reactions in order to achieve stability. Main group elements obey the octet rule in their electronic configuration while the transition elements follow the 18 electron rule. Noble elements have valence shell complete in ground state and hence are said to be stable.
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Which substance is needed in order for this biochemical reaction to occur?
Enzymes are special proteins that act as catalysts, lowering the activation energy of biochemical reactions without changing the reaction's overall free energy profile. ATP often serves as a source of energy, while electron carriers like flavodoxin or ferredoxin may provide necessary electrons for redox reactions.
The substance needed for a biochemical reaction to occur is often a substance that acts as a catalyst, and in biological systems, these are typically enzymes. Enzymes are special proteins that catalyze biochemical reactions by lowering the activation energy required for the reaction to proceed. They bond with reactant molecules, arranging them to facilitate the reaction without altering the reaction's overall free energy profile, thus not affecting the reaction's Gibbs Free Energy (ΔG), and therefore not changing whether a reaction is exergonic or endergonic.
In addition to enzymes, other substances might be required such as a source of energy like adenosine triphosphate (ATP), which is used to drive many complex biochemical reactions. Furthermore, reactions involving the reduction or oxidation of molecules may require electron carriers, like flavodoxin or ferredoxin, to provide the necessary electrons for the process.
Why do you need two ammonium ions and one sulfide ion for the formula for ammonium sulfide?
To form ammonium sulfide, two ammonium ions are needed to balance the 2- charge of one sulfide ion, resulting in the neutral formula (NH4)2S.
Explanation:The student's question pertains to why we need two ammonium ions and one sulfide ion to form the chemical formula for ammonium sulfide. The reason is the charge balance. The ammonium ion (NH4+) carries a 1+ charge, and the sulfide ion (S2-) carries a 2- charge. To neutralize the charges, two ammonium ions are required to balance out the double negative charge of a single sulfide ion. Hence, the formula for ammonium sulfide is (NH4)2S. This is a fundamental concept in ionic bonding where charge neutrality must be achieved.
What happens when electrons are passed from one atom to a more electronegative atom?
What can you predict about an element based on where it is on the periodic table?
Final answer:
The position of an element on the periodic table can predict its valence electrons, chemical reactivity, and whether it's a metal, non-metal, or metalloid. Trends like atomic radius, ionization energy, and electron affinity also correspond to an element's location on the table, allowing for prediction of properties of elements like Francium based on their group.
Explanation:
Predictions Based on the Periodic Table:
The periodic table is a powerful tool that organizes elements by increasing atomic number and groups them based on similar properties. By examining an element's position on the periodic table, we can predict a range of its characteristics.
Group and Period Trends:
Elements in the same group (vertical column) share the same number of valence electrons and tend to display similar chemical behaviors, such as their reactivity and bonding patterns. The position of an element also indicates whether it is a metal, non-metal, or metalloid, with metals typically located on the left side, non-metals on the far right, and metalloids along the zig-zag line separating metals and non-metals.
Periodicity Properties:
Specific trends can be observed as we look horizontally across periods or vertically down groups. Metallurgical traits generally increase as one moves down a group. Furthermore, other properties such as atomic radius, ionization energies, and electron affinities change in a predictable manner across periods and down groups.
Given an element like Francium (Fr), for instance, we can predict its electronic structure, lower ionization energy compared to its predecessor in the group, and even relative melting and boiling points based on its position in group 1. As such, the periodic table not only reflects the elemental order but also serves as a map to infer various attribute trends.
Which of the following ions came from an atom that lost two electrons
Final answer:
An ion from an atom that lost two electrons is a cation with a 2+ charge, such as Ca²⁺ for calcium or Mg²⁺ for magnesium, typically occurring with group 2 elements.
Explanation:
An ion that came from an atom that lost two electrons is known as a cation. This is because when an atom loses electrons it becomes positively charged since it has more protons than electrons. The alkaline earth metals of group 2 in the periodic table are an example of atoms that lose two electrons to form cations with a 2+ charge. When a calcium atom loses two electrons, it forms a Ca²⁺ ion, which is a calcium ion with a 2+ charge. Similarly, a magnesium atom will lose two electrons to form a Mg²⁺ ion, also known as a magnesium ion. These ions have the same number of electrons as the nearest noble gas in the periodic table.
How to find the atomic mass
To find atomic mass, you can use the periodic table and the composition of the molecule, or calculate a weighted average if the element has multiple isotopes.
Explanation:The atomic mass can be found using the periodic table and a few calculation steps. First, determine the atomic masses of each element from the periodic table. Second, count the number of atoms of each element in the molecule. Multiply the atomic mass of each element by the number of atoms of that element. Then, add up all these values.
An atomic mass can also be calculated for an element with multiple isotopes using a weighted average. Here, you multiply the percentage abundance of each isotope (expressed as a decimal) by its respective mass. Add all these values together to get the atomic mass of the element.
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An atom of gold has a mass of 3.271*10^-22g. How many atoms of gold are in 5.00 g of gold?
Why is water the universal solvent? solubility, solute, solvent, dissolve?
Answer:
Water
Explanation:
Suppose that in an ionic compound, "m" represents a metal that could form more than one type of ion. in the formula mf2 , the charge of the m ion would be:
The charge of metal would be +2. Ionic compounds are neutral compounds. It is formed from positively charged ions (cations) and negatively charged ions (anions).
In MF2 is a neutral ionic compound. Therefore, net charge on MF2 is zero. F belongs to halogen family. It gains one electron to get noble gas configuration. So, fluorine has -1 charge.
Hence, charge on metal would be:
Charge of metal + 2*charge of fluorine =0
Charge of metal + 2*(-1) =0
Charge of metal - 2=0
Charge of metal= +2
Thus, we can conclude that, charge of metal in MF2 is +2. i.e., metal loses two electrons to attain noble gas configuration.
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The charge of the M ion in the compound MF2 is -1.
Explanation:The charge of the m ion in the ionic compound MF2 can be determined based on the charges of the other ions present in the compound. Since F is a Group 17 element and forms an ion with a charge of -1, the charge of the M ion can be calculated using the formula:
2(M) + 2(F) = 02(M) = -2(F)M = -1Therefore, the charge of the M ion in the compound MF2 is -1.
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How many moles of aluminum do 5.6×1024 aluminum atoms represent? express your answer using two significant figures?
We can convert the number of atoms to moles using Avogadro's number (6.022 x 10^23). In this case, 5.6 x 10^24 atoms of aluminum equates to 9.3 moles of aluminum when expressed to two significant figures.
Explanation:To convert the number of aluminum atoms to moles, we use Avogadro's number, which is 6.022 x 10^23. This number represents the number of atoms in one mole of any substance. Hence, to figure out the number of moles from a certain number of atoms, we divide the given number of atoms by Avogadro's number.
So, for 5.6 x 10^24 atoms of aluminum,
Moles = Total Aluminum atoms / Avogadro's number
= 5.6 x 10^24 / 6.022 x 10^23
= 9.29 moles
Expressed to two significant figures, the answer will be 9.3 moles of aluminum.
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Write a nuclear equation for the fusion of two H−2 atoms to form He−3 and one neutron.