pls help 8th grade k12
What is the SI unit of time?
OA.
second
OB.
minute
OC. hour
OD. day
Res
[tex]▪▪▪▪▪▪▪▪▪▪▪▪▪ {\huge\mathfrak{Answer}}▪▪▪▪▪▪▪▪▪▪▪▪▪▪[/tex]
The correct choice is ~ A
S.I unit of time is Second
Chemical properties of mercury hg
Answer:
Mercury has a relatively high vapour pressure and the highest volatility of any metal, vapourizing to become a colourless, odourless gas. The metal is a fair conductor of electricity, but a poor conductor of heat. Mercury's atomic number is 8.
Physical change does not produce a nee substance true or false
Answer:
ooooooooh .,.,.,.,.,.,
Answer:
True
TruePhysical change – A change in the size, shape, color, or state of matter of a substance. No new substance is produced.
Suppose you have samples of three unknown solids. Explain how you could use their properties to
determine whether or not they are ionic solids.
Using melting and boiling temperature, hardness and electric current passing testing.
Ionic solidsIonic solids are materials that have a strong bond between their ions, thus producing well-defined shapes.
In addition, due to this strong attraction, the boiling and melting temperatures of these materials are very high, in addition to the resistance to breakage presented by them.
Finally, ionic solids are also excellent conductors of electricity.
So, their properties used to determine whether or not they are ionic solids are melting and boiling temperature, hardness and electric current passing testing.
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The EPA has used the slogan “Ozone: good up high, bad nearby” in some of its publications for the general public. Explain the message
Answer:
------------------------------
Explanation:
---------------
Escriba un poema usando 4 de las siguientes palabras: lluvia, nieve, lluvia, granizo, tornado, huracanes, frente cálido, frente frío, alta presión, baja presión, termómetro, barómetro, anemómetro, pluviómetro, veleta o higrómetro.
plis ayúdenme porfa
Answer:
i dont speak mexican
Explanation:
Someone please help me :)))
Answer:
3. solids are measured in centimeters
4. gases And liquids are measured in milliliters
Answer:
Solids are measured in Mass
Gases and Liquids are measured in Volume
Explanation:
Solids can also additionally be measured by length as well.
fun fact: natural gas is measured by volume (cubic feet) but is sold based on its heating content (Btus). A cubic foot of natural gas is the amount of natural gas that can be contained in a cube one foot on a side, at a certain standard temperature and pressure. (source; oilgaslawyer blog)
he hybridization of carbon in diamond is _________. Enter your answer with no superscripts or subscripts, i.e., ab3.
Diamond is composed of hexagonal rings in which sp3 hybridized carbon atoms are linked together.
Hybridization refers to the mixing of atomic orbitals to yield hybrid orbitals that are suitable for bonding. The energy of orbitals that combine to form hybrid orbitals must be close enough for such combination to take place.
Diamond is composed of hexagonal rings in which sp3 hbridized carbon atoms are linked together. Each carbon atom in diamond is tetrahedral.
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The mixing of the two different orbitals to form a compound is called hybridization. For example mixing of s and p orbits.
The correct answer is sp3.
The arrangement of the elements in a different manner to form a new compound is called allotropes. For example, diamond and graphite are the allotropes of carbon.
The valence electrons are in p orbitals and p orbit mixed after the s orbitals.
Therefore, the correct answer is sp3
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During a class presentation, your classmate explains that plants perform photosynthesis and animals perform cellular respiration. In your own words, describe what these processes are and explain why your classmate’s statement is correct or incorrect.
My classmate's statement in incorrect because plants are also composed of cells.
All living things are composed of cells. A cell is the smallest unit of living organisms. Cells obtain energy via the process of cellular respiration. During cellular respiration, glucose is broken down to yield carbon dioxide and water.
In photosynthesis, carbon dioxide and water are combined to form glucose. The two processes are opposites of each other. Plants produce their own food via photosynthesis. Since plants are composed of cells, plant cells also undergo cellular respiration therefore my classmate's statement in incorrect.
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Sodium hydroxide neutralises hydrochloric acid as shown in the equation:
NaOH(aq) + HCl(aq) i NaCl(aq) + H2O(l)
(4)
dm3
(3)
The student found that 27.20 cm3 of 0.100 moles per dm3 sodium hydroxide neutralised 5.00 cm3 of hydrochloric acid.
Calculate the concentration of the hydrochloric acid in moles per dm3.
Give your answer to three significant figures.
Explanation:
Mole ratio of NaOH : HCl = 1: 1
Moles of NaOH used = 0.1 mol/1000 cm3 × 27.20 cm3
= 2.72 × 10^-3 mol
Therefore moles of HCl used is also 2.72 × 10^-3 mol
So concentration of HCl can be found by dividing the no.of moles of HCl by the volume of HCl as follows
2.72 × 10^-3 mol/ 5cm3
1000cm3 = 1dm3
Therefore,
1cm3 = 1/1000 dm3
5cm3 = 5/1000 dm3
HCl conc. = 2.72 × 10^-3 mol/ 5×10^-3 dm3
= 0.544 moldm-3
BaCO3 Draw the Lewis dot structure for BaCO3. Include all nonbonding electrons. Show the formal charges of all atoms. To change the symbol of an atom, double-click on the atom and enter the letter of the new atom
To draw the Lewis dot structure on the [tex]B_aCO_3[/tex] molecular it is necessary to show the electron sharing between the [tex]CO_3[/tex] molecules, and then show the ionic bond between [tex]B_a[/tex] and [tex]CO_3[/tex].
You can see how this is done in the attached image.
We can arrive at this answer because:
The Lewis dot structure is made to show the sharing or transmission of electrons between atoms.In the [tex]B_aCO_3[/tex] molecule, we have both sharing and transmission of electrons, which occurs for atoms to search for stability in their valence layers.The compound [tex]CO_3[/tex] has covalent bonds, where the electrons share the electrons so that each one is electronically stable.However, the [tex]B_a[/tex] atom needs to transmit two electrons to another molecule to achieve stability, so when it forms a bond with [tex]CO_3[/tex], it transmits two electrons to that compound.This causes [tex]CO_3[/tex] to be negatively charged, while [tex]B_a[/tex] is positively charged.Therefore, we can say that [tex]B_a[/tex] forms an ionic bond with [tex]CO_3[/tex].
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answer this please thank you
Answer:
Explanation:
D is the correct answer
The concept that the total amount of energy remains the same is called.
Answer:The law of conservation of energy
Explanation:
states that the total energy is constant in any process. Energy may change in form or be transferred from one system to another, but the total remains the same.
A compound consists of 75% magnesium and 25% oxygen. Find the empirical formula.
% Composition of elements:
Magnesium = 75%Oxygen = 25%Atomic mass of given elements:
Magnesium = 24 gOxygen = 16 gNow, divide % composition by Atomic mass:
[tex]\footnotesize\implies Mg = \dfrac{\% \: Composition}{Atomic \: mass} = \dfrac{75}{24} = \bf 3.125[/tex]
[tex]\footnotesize\implies O = \dfrac{\% \: Composition}{Atomic \: mass} = \dfrac{25}{16} = \bf 1.5625[/tex]
Simplest Ratio:
[tex]\footnotesize\implies Mg = \dfrac{3.125}{1.5625} = 2[/tex]
[tex]\footnotesize\implies O = \dfrac{1.5625}{1.5625} = 1[/tex]
Empirical Formula:
[tex]\footnotesize\implies \underline{ \boxed{ \red{ \bf Empirical \: Formula = Mg_2O}}}[/tex]
The empirical formula will be [tex]Mg_{2}[/tex] .
What is empirical formula?The simplest entire number fraction of atoms contained in a chemical molecule is its empirical formula.
Calculation of empirical formula:
It is given that, composition of Mg = 75 %, composition of oxygen = 25%.
It is known that, atomic mass of Mg = 24 g, atomic mass of oxygen = 16g.
By dividing % composition by atomic mass of given elements:
Mg = % composition / %atomic mass
= 75 / 24
= 3.125
Oxygen (O) = % Composition / atomic mass
= 25 / 1.56
Now, calculate simplest ratio of Mg and O.
For Mg = 3.125 / 1.56
= 2.
For O = 1.56 / 1.56
= 1
So, the empirical formula will be [tex]Mg_{2}O[/tex].
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In the laboratory you are asked to make a 0.282 m manganese(II) acetate solution using 315 grams of water. How many grams of manganese(II) acetate should you add
Answer:315 - 282 = 173?
Explanation:
How many double bonds does CCL2H2 have?
1: Given that Ka for HCOOH is 1.8×10^-4 at 25°C what is the value of b for COOH− at 25 °C?
Kb=
2: Given that b for (CH3)2 NH is 5.4×10^-4 at 25°C, what is the value of Ka for (CH3)2NH+2 at 25 °C?
Ka=
Explanation:
At 25 °C Dissociation constant of water or Kw = 1× 10^-14 mol2dm-6
Ka × Kb = Kw for all diluted solutions
Ka×Kb = 1 × 10^-14 mol2dm-6
Therefore for question 1 -
COOH- is the conjugate base for HCOOH ( we find the conjugate base by removing an H atom and the Conjugate acid by adding an H atom)
COOH- (aq) + H2O ( l) <-----> HCOOH( aq) + OH-(aq)
So we can apply the above mentioned equation to find Kb value for COOH-
Kb = 5.56 × 10^-11 moldm-3
For question 2-
We can see that (CH3)2NH+2 is the conjugate acid of (CH3)2 NH. (A H atom has been removed so the one with a H atom less is the conjugate base.)
(CH3)2NH+2 (aq) + H2O (l) <-----> (CH3)2 NH (aq) + H3O+ (aq)
So applying the previously mentioned equation we get Ka = 1.85 × 10^-11 moldm-3
Balance the following redox reaction if it occurs in acidic solution. What are the coefficients in front of Ni and H+ in the balanced reaction? Ni2+(aq) + NH4+(aq) → Ni(s) + NO3-(aq)
In this case, the problem is asking for the balance of a redox reaction in acidic media, in which nickel is reduced to a metallic way and nitrogen oxidized to an ionic way.
Thus, according to the given information, it turns out possible for us to balance this equation in acidic solution by firstly setting up the half reactions:
[tex]Ni^{2+}+2e^-\rightarrow Ni^0\\\\N^{3-}H_4^++3H_2O\rightarrow N^{5+}O_3^-+8e^-+10H^+[/tex]
Next, we cross multiply each half-reaction by the other's carried electrons:
[tex]8Ni^{2+}+16e^-\rightarrow 8Ni^0\\\\2N^{3-}H_4^++6H_2O\rightarrow 2N^{5+}O_3^-+16e^-+20H^+[/tex]
Finally, we add them together to obtain:
[tex]8Ni^{2+}+2N^{3-}H_4^++6H_2O\rightarrow 8Ni^0+2N^{5+}O_3^-+20H^+[/tex]
Which can be all simplified by a factor of 2 to obtain:
[tex]4Ni^{2+}+N^{3-}H_4^++3H_2O\rightarrow 4Ni^0+N^{5+}O_3^-+10H^+\\\\4Ni^{2+}(aq)+NH_4^+(aq)+3H_2O(l)\rightarrow 4Ni(s)+NO_3^-(aq)+10H^+(aq)[/tex]
Hence, the coefficients in front of Ni and H⁺ are 4 and 10 respectively.
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Determine the mass in grams of 5.15 × 10²¹ atoms of chromium. (The mass of one mole of chromium is 52.00 g.)
The mass of 5.15 × 10²¹ atoms of chromium is 0.44 g
From Avogadro's hypothesis,
6.02×10²³ atoms = 1 mole of Cr
But:
1 mole of Cr = 52 g
Thus, we can say that:
6.02×10²³ atoms = 52 g of Cr
With the above information, we can obtain the mass of 5.15 × 10²¹ atoms of chromium. This can be obtained as follow:
6.02×10²³ atoms = 52 g of Cr
Therefore,
5.15×10²¹ atoms = (5.15×10²¹ × 52) / 6.02×10²³
5.15×10²¹ atoms = 0.44 g of Cr
Thus, the mass of 5.15 × 10²¹ atoms of chromium is 0.44 g
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A 4.0 L sample of gas has a pressure of 300 kPa at 250K. What will the volume be if the pressure is increased to 500 kPa and the temperature is decreased to 200 K?
Answer:A versatile Ideal Gas Laws calculator with which you can calculate the pressure, volume, quantity (moles) or temperature of an ideal gas, given the other three. Free online gas law calculator a.k.a. PV = nRT calculator which accepts different input metric units such as temperature in celsius, fahrenheit, kelvin; pressure in pascals, bars, atmospheres; volume in both metric and imperial units ...
A hydrochloric acid solution is standardized by titrating 0.2329 g of primary standard sodium carbonate to a methyl red end point by boiling the carbonate solution near the end point to remove carbon dioxide. If 42.87 mL acid is required for the titration, what is its molarity
HELP
The molarity of the acid, HCl solution is 0.103 M
We'll begin by calculating the number of mole in 0.2329 g of Na₂CO₃
Mass of Na₂CO₃ = 0.2329 g
Molar mass of Na₂CO₃ = (23×2) + 12 + (16×3) = 106 g/mol
Mole of Na₂CO₃ =?Mole = mass / molar mass
Mole of Na₂CO₃ = 0.2329 / 106
Mole of Na₂CO₃ = 0.0022 mole Next, we shall determine the number of mole of HCl needed to react with 0.0022 mole of Na₂CO₃Na₂CO₃ + 2HCl —> 2NaCl + H₂O + CO₂
From the balanced equation above,
1 mole of Na₂CO₃ reacted with 2 moles of HCl.
Therefore,
0.0022 mole of Na₂CO₃ will react with = 0.0022 × 2 = 0.0044 mole of HCl
Finally, we shall determine the molarity of the HCl.Mole of HCl = 0.0044 mole
Volume = 42.87 mL = 42.87 / 1000 = 0.04287 L
Molarity of HCl =?Molarity = mole / Volume
Molarity of HCl = 0.0044 / 0.04287
Molarity of HCl = 0.103 MThus, the molarity of the acid, HCl solution is 0.103 M
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Magnesium metal burns in air with an intense bright light according to the equation
2 Mg(s) + O2(g) → 2 MgO(s) + 1200 kJ
A.) What is the amount of energy in kJ produced when 4.5 mol of Mg is burned in the presence of excess oxygen?
The heat produced by 4.5 moles of magnesium when burnt is 2700 kJ.
A thermochemical reaction is a reaction in which the amount of heat lost or gained is included in the reaction equation. The thermochemical reaction equation for the combustion of magnesium is shown as follows;
2 Mg(s) + O2(g) → 2 MgO(s) + 1200 kJ
From the reaction equation;
2 moles of magnesium produced 1200 kJ of heat
4.5 moles of magnesium will produce 4.5 moles × 1200 kJ/2 moles
= 2700 kJ
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Consider the evaporation of water. The standard change in the free energy is positive with ΔG∘rxn=+8.59kJmol. One might expect this process to occur in the opposite direction, with water vapor condensing into liquid water. How can the evaporation be spontaneously under normal conditions?
Answer:
The partial pressure of water is much less than 1atm, so the free energy change for the process must be negative with ΔGrxn<0.
Explanation:
Water vapor will condense into liquid water when the water vapor is in its standard state, with a pressure of 1atm. Under normal circumstances, the partial pressure of water vapor is much less that 1atm. It is in a nonstandard state. The free energy change of this reaction has to be negative in order to make the reaction spontaneous.
The criteria of the spontaneous process are the change in the Gibbs free energy should be negative. Above the normal boiling point, the TΔS will be greater than ΔH and ΔG<0.
What is Gibbs's free energy?Gibbs free energy can be described as a state function therefore it doesn’t depend on the path. The change in free energy is equal to the change in enthalpy minus the product of entropy change and temperature of the system.
ΔG = ΔH - Δ (TS)
If the process is carried out at constant temperature, ΔT = 0:
ΔG = ΔH – TΔS
ΔG > 0 for the reaction is non-spontaneous, ΔG < 0 for the reaction is spontaneous, exergonic and ΔG = 0 for the reaction is at equilibrium.
Spontaneous can be described as a reaction that occurs by itself without any external action towards it. The non-spontaneous process needs constant external energy applied to continue and as the external action, the process will cease.
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How many carbon dioxide molecules and water molecules are needed to make one molecule of glucose?
Answer:
It takes six molecules of carbon dioxide and six molecules of water to make one molecule of glucose.
true or false, Electromagnetic radiation with a higher energy, travels with higher speed than electromagnetic radiation with a lower energy
Answer:
True.
Explanation:
Since electromagnetic radiation travels in waves, we can assume that the more high energy the waves are, the faster they will go. So therefore, higher energy travels faster.
Hope that helps you!
Answer:
True
Explanation:
Because electron delocalization stabilizes a compound, if the only way electrons can be moved is away from the most electroneagtive atom, that is better than no electron delocalization at all.
a. True
b. False
As electron delocalization stabilizes the compound it is necessary that it takes place for compound to exist , hence the given statement is false.
What is a compound?Compound is defined as a chemical substance made up of identical molecules containing atoms from more than one type of chemical element.
Molecule consisting atoms of only one element is not called compound.It is transformed into new substances during chemical reactions. There are four major types of compounds depending on chemical bonding present in them.They are:
1)Molecular compounds where in atoms are joined by covalent bonds.
2) ionic compounds where atoms are joined by ionic bond.
3)Inter-metallic compounds where atoms are held by metallic bonds
4) co-ordination complexes where atoms are held by co-ordinate bonds.
They have a unique chemical structure held together by chemical bonds .Compounds have different properties as those of elements because when a compound is formed the properties of the substance are totally altered.
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Select all of the true statements about hydrocarbon structure.
a. Every hydrocarbon molecule is exactly the same as every other one.
b. The ability of carbon atoms to bond strongly to each other allows them to stably form ringed structures.
c. Hydrocarbons contain only single bonds that easily break down into smaller compounds.
d. Hydrocarbons are organic chemical compounds that consist of carbon and hydrogen.
Answer:
C
Explanation:
Organic compounds are the compounds which are made only from carbon and hydrogen. The correct option is option D that is hydrocarbons are organic chemical compounds that consist of carbon and hydrogen.
What is chemical Compound?Chemical Compound is a combination of molecule, Molecule forms by combination of element and element forms by combination of atoms in fixed proportion.
There are two types of compound covalent compound and ionic in chemistry, covalent compound formed by sharing of electron and ionic compound formed by complete transfer of electron. Hydrocarbons are organic compound. Hydrocarbon can have linear chain structure, ring structure or branched structure.
Therefore, hydrocarbons are organic chemical compounds that consist of carbon and hydrogen. The correct option is option D.
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H3PO4 + KOH yields K3 PO4 + H2O
need help balancing
Answer:
H3PO4 + 3KOH---------> K3PO4 + 3H2O
Explanation
H3PO4 + KOH------------> K3PO4 + H20
when an hydrogen ion containing acid (HX) reacts with a hydroxide containing base(BOH) they produce water and a "salt".
water can be called dihydrogen oxide (H2O), but it can also be called
hydrogen hydroxide (HOH)...same thing.
so the phosphoric acid (H3PO4) contains 3 hydrogen ions (H), and needs 3
hydroxide ions to from 3 hydrogen hydroxides .. that is 3 waters AND A "SALT" WITH THE REMAINING SPECIES ( K AND PO4)
so let us balance
H3PO4 + 3KOH--------->K3PO4 + 3HOH or
H3PO4 + 3KOH---------> K3PO4 + 3H2O
Check:
6 H on the left side, 6 H on the right side
1 P on the left side, 1 P on the right side
3 K on the left side, 3 K on the right side
7 O on the left side, 7 O on the right side
abadabaabdabadaba........that's all folks
yup it is balanced