Chemistry High School
a. ELEMENT: Asubstancethatcannotbe decomposed (broken down)into simpler substances by ordinary chemicalmeans.
Doreen schmidt is a chemist. she needs to prepare 3232 ouncesounces of a 1010% hydrochloric acid solution. find the amount of 1616% solution and the amount of 88% solution she should mix to get this solution.
24 ounces of 8% solution and 8 ounces of 16% solution to create 32 ounces of 10% solution.
OK. We need 32 ounces of 10% solution and we have 16% and 8% solutions available. So let's set up an equation to solve. I'll use the variable X to represent the amount of 8% solution needed.
X*0.08 + (32-X)*0.16 = 32*0.10
Now simplify and solve.
X*0.08 + (32-X)*0.16 = 32*0.10
X*0.08 + 32*0.16 - X*0.16 = 32*0.10
X*0.08 - X*0.16 = 32*0.10 - 32*0.16
X(0.08 - 0.16) = 32(0.10 - 0.16)
X(-0.08) = 32(-0.06)
X = 32(-0.06)/(-0.08)
X = 24
So we need 24 ounces of 8% solution and (32 - 24) = 8 ounces of 16% solution.
It takes 42.0 min for the concentration of a reactant in a first–order reaction to drop from 0.45 m to 0.32 m at 25°c. how long will it take for the reaction to be 90% complete?
Answer is: 284 min.
t₁ = 42 min = 2520 s.
t₂ = ?
c₁ = 0,45 mol/L.
c₂ = 0,32 mol/L.
Theintegrated first order rate lawis:
ln(c₂/c₁) = -k·t.
ln(0,32 mol/L÷0,45 mol/L) = -k·2520 s.
k = 0,34 ÷ 2520 s.
k = 0,000135 1/s.
For 90%: ln(0,045 mol/L÷ 0,45 mol/L) = -0,000135 1/s· t.
t = 2,30÷ 0,000135 1/s.
t = 17056 s = 284 min.
A chemical reaction in which the rate of reaction is directly proportional to the concentration of the reacting substance.
The example of the first-order reaction is as follows:-
- The hydrolysis of aspirin
- The reaction of t-butyl bromide with water
To solve this question, the formula we are using this as follows:-
The integrated first order rate law is:
For 90% :
t =284 mins
Hence, the time required to complete 90% of the reaction is 284 mins.
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How are isotopes defined?forms of different elements that have the same number of neutrons in each atomforms of different elements that have the same number of protons in each atomforms of the same element that differ in the number of neutrons in each atomforms of the same element that differ in the number of protons in each atom?
Answer: Option (c) is the correct answer.
When there are same number of protons but different number of neutrons in the nuclei of two or more forms of an atom then they are known as isotopes.
For example, and are isotopes.
Thus, we can conclude that out of the following options, isotopes are defined as forms of the same element that differ in the number of neutrons in each atom.
Your answer is C forms of the same element that differ in the number of neutrons in each atom because if the number of neutrons change the whole element changes.
A neutral atom in its ground state contains 28 electrons. this element is considered a ________ element, and has _______ electrons in orbitals with l = 2. actinide, 10 transition, 10 transition, 8 main group, 8 main group, 10
A neutral atom in its ground state contains 28 electrons. this element is considered atransitionelement, and has 8 electrons in orbitals with l = 2.
Electron configuration:₂₈X 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s².
l is azimuthal quantum number, l = 2describes d orbital. There is eight electrons in 3d orbital.
transition, 8 electrons
The element in question is nickel. Nickel is a transition metal belonging to group10 in the periodic table. Its electron configuration is [Ar]4s2 3d8. Hence it has eight electrons in the d(l=2) orbital.
This is the ground state electron configuration of the transition metal nickel.
A tetrahedral molecule has ___ regions of high electron density around the central atom. these molecules have central atoms with ___ lone pairs and ___ atoms bonded to them.
The answer is "A tetrahedral molecule has 4 regions of high electron density around the central atom. These molecules have central atoms with 0 lone pairs and 4 atoms bonded to them." Based on the octet rule, the atom must have 8 electrons to become stable. As a result, the molecule will not have lone pairs.
Answer : A tetrahedral molecule has 4 regions of high electron density around the central atom. These molecules have central atoms with 0 lone pairs and 4 atoms bonded to them.
As we are given the molecular geometry of the molecule that is tetrahedral and the hybridization of tetrahedral molecule is, .
That means the number of electron density around the central atom is 4 and the electronic geometry or the molecular geometry of the molecule will be tetrahedral.
And these molecule have central atoms with zero (0) lone pair and four (4) atoms bonded to them.
For example : In molecule, the central atom is carbon and neighboring atoms are 4 hydrogen atoms. The number of electron density is 4 that means the hybridization will be and the electronic geometry or the molecular geometry of the molecule will be tetrahedral.
In molecule, the central atom (carbon) has zero lone pair and the central atom (carbon) bonded with 4 hydrogen atoms.
A particular carbon isotope has an atomic number of 6 and an atomic mass of 14. the respective number of neutrons, protons, and electrons that this carbon isotope has is _____.
Answer: 8 neutrons, 6 protons and 6 electrons
Isotopes are elements which have same atomic number but different mass number.
Atomic number is defined as the number of protons or number of electrons that are present in an electrically neutral atom.
Atomic number = Number of electrons = Number of protons = 6
Mass number is defined as the sum of number of protons and neutrons that are present in an atom.
Mass number = Number of protons + Number of neutrons = 14
Number of protons + Number of neutrons = 14
6 + Number of neutrons = 14
Number of neutrons = 8
Thus there are 8 neutrons, 6 protons and 6 electrons in carbon isotope.
8 neutrons 6 protons and 6 electrons
A potato contains 20 g of carbohydrate. if carbohydrate has a caloric value of 4 kcal/g, how many kcal are obtained from the carbohydrate in the potato?
It's a simple multiplication question. 20 grams of carbohydrate present in 1 potato. As per the instructions Carbohydrate has 4kal/gram. To get the answer for how many kilocalorie carbohydrate is present in one potato, we have to multiply (20 x 4 ) that is 80 kcal.
80 kcal will obtained from a potato
It is defined as the total released by the complete combustion of specified amount of fuel or food. It is generally measured in kcal/g or J/g.
Calorific value of carbohydrate = 4 kcal/g
Amount of carbohydrate in potato = 20 g
1 g of carbohydrate gives 4 kcal of energy
20 of carbohydrate will give
= 20 × 4
= 80 kcal
So, the given potato will give 80 kcal.
A sample of potassium nitrate (49.0 g) is dissolved in 101 g of water at 100 °c, with precautions taken to avoid evaporation of any water. the solution is cooled to 30.0 °c and no precipitate is observed. this solution is __________. a sample of potassium nitrate (49.0 g) is dissolved in 101 g of water at 100 °c, with precautions taken to avoid evaporation of any water. the solution is cooled to 30.0 °c and no precipitate is observed. this solution is __________. hydrated saturated unsaturated supersaturated placated
The solution is supersaturated. because it contains a higher concentration of solute than does a saturated solution at that temperature.
and also because the solution which has no precipitation and had cooled at this temperature should be a supersaturated solution.
Why does perchloric acid cause macromolecules to precipitate?
Perchloric acid (HCO₄) is one of strongest inorganic acids.Perchloric acid precipitation is used to removes most of the protein present in the sample and stabilize many of the small molecule analytes. It can use also to precipitationglycogen, ATP, glutathione, antioxidants.
Perchloric acid donates protons to macromoleculesand lower their solubility in water. Also perchloric acid is strong oxidizing agent and change oxidation number of elements.
Which pair of elements would you expect to exhibit the greatest similarity in their physical and chemical properties? o,s si, p?
I believe the appropriate pair is O and S, Periodic table represents arrangements of elements ordered by their atomic number,physical and chemical properties. Both sulfur and oxygen are in the same group of the periodic table (group 6), they have a valency of 2, This means they have a greater similarity in chemical and physical properties.
Which compound is an electrolyte? sodium hydroxide sugar carbon tetrachloride rubbing alcohol?
Answer: sodium hydroxide
Electrolyte is a substance which dissociates into ions when dissolved in water and thus is able to conduct electric current through them. Ionic compounds dissociate in water to give ions and thus acts as electrolytes.
Compounds in solid form does not conduct electricity due to the absence of free ions.
Sodium hydroxide is an ionic compound which dissociates to give sodium and hydroxide ions.
Sugar, carbon tetrachloride, rubbing alcohol are covalent compounds and thus do not dissociate to give ions and thus do not act as electrolytes.
You put this in the wrong subject but its sodium hydroxide :)
hope this helped
What is the percent yield of a reaction in which 200. g of phosphorus trichloride reacts with excess water to form 91.0 g of hcl and aqueous phosphorous acid (h3po3)?
Answer is:yield of a reaction is 56,4%.
Chemical reaction: PCl₃ + 3H₂O → 3HCl + H₃PO₃.
m(PCl₃) = 200 g.
m(HCl) = 91,0 g.
n(PCl₃) = m(PCl₃)÷ M(PCl₃).
n(PCl₃) = 200 g÷ 137,33 g/mol.
n(PCl₃) = 1,46 mol.
n(HCl) = m(HCl)÷ M(HCl).
n(HCl) = 91 g÷ 36,45 g/mol.
n(HCl) = 2,47 mol.
From reaction: n(PCl₃) : n(HCl) = 1 : 3.
n(HCl) = 1,46 mol· 3 = 4,38 mol.
Yield of reaction: 2,47 mol÷ 4,38 mol· 100% = 56,4%.
The percentage yield of HCl obtained from the reaction is 57.1%
We'll begin by calculating the mass of PCl₃ that reacted and the mass of HCl produced from the reaction.
PCl₃ + 3H₂O → 3HCl + H₃PO₃
Molar mass of PCl₃ = 31 + (3×35.5) = 137.5 g/mol
Mass of PCl₃ from the balanced equation = 1 × 137.5 = 137.5 g
Molar mass of HCl = 1 + 35.5 = 36.5 g/mol
Mass of HCl from the balanced equation = 3 × 36.5 = 109.5 g
From the balanced equation above,
137.5 g of PCl₃ reacted to produce 109.5 g of HCl
- Next, we shall determine the theoretical yield of HCl.
From the balanced equation above,
137.5 g of PCl₃ reacted to produce 109.5 g of HCl.
200 g of PCl₃ will react to produce = k200 × 109.5) / 137.5 = 159.3 g of HCl.
- Finally, we shall determine the percentage yield.
Actual yield of HCl = 91 g
Theoretical yield of HCl = 159.3 g
Percentage yield =?
Percentage yield of HCl = 57.1%
Learn more: brainly.com/question/15874979
At constant volume, you cool a sealed, air-filled can, and the pressure reduces by half. which of the following happens? half of the gas leaks out
the temp of the air reduces by half
the spaces between the gas molecules shrink
the number of collisions per unit area doubles
Answer is:the temperature of the air reduces by half.
The Pressure Temperature Law -the pressure of a given amount of gas held at constant volume is directly proportional to the temperature:
P₁/T₁ = P₂/T₂.
P₁ = 2P₂.
2P₂/T₁ = P₂/T₂.
T₂ = T₁P₂/2P₂.
T₂ = T₁/2.
As the pressure goes down, the temperature also goes down.
What do you observe when you move two hydrogen atoms closer together?
1-They will form the weakest bond.
2-The energy between them begins to decrease as they get closer, and it reaches the minimum when the two atoms are at an optimum distance apart.
3-But once the two atoms forced closer together, So the energy rapidly increases
What fact about elements would help explain why two elements would bond with the same element in the same proportion? a.the elements are on the same side of the staircase.
b.the elements are in the same period on the periodic table.
c.the elements are next to each other on the periodic table.
d.the elements are found in the same column on the periodic table?
The first 2 elements are found in the same column.
For example Na and K would both bond with O giving Na2O and K2O. Both Na and K are in the same column.
The answer is D
If you have 0.5 L of air in a rigid, sealed container at a pressure of 203 kPA and a temp of 203. You heat the contain to 273 K. What is the final pressure of the air? 151 kPA
Volume remains constant: P1 x T2 = P2 x T1. Pressure increases in direct proportion to absolute temperature increase.
203kPa x 273K = P2 x 203K = P2 x 55,419.
P2 = 55,419 / 203 = 273kPa final pressure.
The decomposition of potassium chlorate, kclo3, is used as a source of oxygen in the laboratory. how many moles of potassium chlorate are needed to produce 15 moles of oxygen gas? worksheet
2KClO3 ===> 2KCl + 3O2
Set up a Proportion
2 mols KClO3 . . . . . . . . . . . x
========= . . . . . . . . . . . ==============
3 moles of Oxygen . . . . . . 15 moles of oxygen
2/3 = x / 15 Cross Multiply.
2 * 15 = 3x
30 = 3x
x = 30 / 3
x = 10
So to get 15 moles of oxygen, you need 10 moles of KClO3
For real gases, how does a change in pressure affect the ratio or pv to nrt?
First the compressibility factor Z= PV/nRT
For the ideal gas, the compressibility factor is Z = 1.
But the real gases The value of Z generally increase with increasing pressure:
1- At high pressure (the gas hard to compress): attractive force is weaker than the repulsive force for the gas, and its real molar volume gets larger than the ideal molar volume, and that means z >1.
2- At low pressure (the gas easy to compress): attractive force is stronger than the repulsive force for the gas, and its real molar volume gets smaller than the ideal volume, and that means Z
Explain why it is important to reduce coefficients in a balanced equation to the lowest possible whole number ratio
Answer is: it is important because in that way chemist can see lowest possible number of reactants in chemicalreaction needed to form product of reaction. Coefficients with the lowest ratio indicate the relative amounts of substances in a reaction.
For example, chemical reaction: 2H₂ + O₂ → 2H₂O.
It can be seen that there are two molecules of hydrogen, one molecule of oxygen and molecule of water in reaction.
Why is it possible to safely drink a solution that contains a 50:50 mixture of equal concentrations of a strong acid and a strong base, either of which, if ingested separately, would be very caustic and damaging?
Because a 50 50 solution of equal concentrations of acid and base neutralize each other and you will get basically a complete neutral substance like water