preparing a given volume of a solution that has a specific molarity is a very important skill for a chemist. one step in that process is calculating the mass of solute required.
What mass of solute is required to produce 429.5 mL of a 0.256 M solution of KBr? _______ g KBr

Answer:

The reaction is exothermic as the solution becomes warm.

Explanation:

Hello there!

In this case according to the described reaction between sodium metal and water, we can write up the chemical equation whereas the products turn out to be sodium hydroxide and hydrogen gas:

[tex]2Na+2H_2O\rightarrow 2NaOH+H_2[/tex]

Moreover, these reactions are known to be highly exothermic, for that reason the solution becomes warm as the reaction releases heat as it goes to completion.

Best regards!

Answer:

left is chemical because its chemicals, and right is physical because the ice cream is melting and thats physical

Explanation:

In the given reaction, 4 moles of KO2 react to produce 3 moles of O2. Therefore, if 10.5 moles of carbon dioxide (CO2) are used at STP, an equal amount of oxygen (O2) is produced. Hence, 10.5 moles of O2 will be generated.

According to the balanced chemical equation, the reaction 4 KO2(s) + 2 CO2(g) → 2 K2CO3(s) + 3 O2(g) shows that for every 4 moles of KO2, 3 moles of O2 are produced. Therefore, the molar ratio between KO2 and O2 is 4:3.

Since 10.5 moles of CO2 are used, we can use the stoichiometry of the reaction to determine the amount of O2 produced. As the reaction equation does not involve CO2, the amount of CO2 used does not directly affect the production of O2. Thus, 10.5 moles of CO2 will yield an equal amount of O2, resulting in 10.5 moles of O2 being produced at STP.

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The balanced equation is 6 Pb(s) + 6 Cr2O72-(aq) + 42 H+(aq) → 12 Cr3+(aq) + 42 H2O(l) + 6 Pb2+(aq). 6 moles of Pb(s) are oxidized for every 6 moles of Cr2O72- consumed. If 5 moles of Cr2O72- are used, it will oxidize 5 moles of Pb(s).

First, we need to balance the two half-reactions. Let's start with the reduction half-reaction of Cr2O72-: Cr2O72-(aq) + 14 H+(aq) + 6 e- → 2 Cr3+(aq) + 7 H2O(l).  To balance the oxygen atoms, we add 7 H2O to the left side: Cr2O72-(aq) + 14 H+(aq) + 6 e- → 2 Cr3+(aq) + 7 H2O(l). Next, we balance the hydrogen atoms by adding 14 H+ to the right side:

Cr2O72-(aq) + 14 H+(aq) + 6 e- → 2 Cr3+(aq) + 7 H2O(l) + 14 H+(aq)

Now, let's balance the oxidation half-reaction of Pb: Pb(s) → Pb2+(aq) + 2 e-. The equation is already balanced. To combine the two half-reactions, we multiply the reduction half-reaction by 6 and the oxidation half-reaction by 6 to ensure that the electrons cancel out: 6 Cr2O72-(aq) + 42 H+(aq) + 36 e- → 12 Cr3+(aq) + 42 H2O(l) + 84 H+(aq). 6 Pb(s) → 6 Pb2+(aq) + 12 e-. Now, we can write the balanced equation: 6 Pb(s) + 6 Cr2O72-(aq) + 42 H+(aq) → 12 Cr3+(aq) + 42 H2O(l) + 6 Pb2+(aq).

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The major E2 reaction product formed when (1R,2S,4S)-2-chloro-4-methyl-1-(propan-2-yl)cyclohexane reacts with hydroxide ion in DMSO is (1S,2R,4S)-2-methyl-1-(propan-2-yl)cyclohexene.

In an E2 (elimination) reaction, a hydrogen atom and a leaving group are removed from adjacent carbon atoms, resulting in the formation of a double bond. In this case, the leaving group is the chloride ion (Cl-) and the hydrogen atom is removed from the carbon adjacent to the chlorine atom.

The given starting compound, (1R,2S,4S)-2-chloro-4-methyl-1-(propan-2-yl)cyclohexane, has a chiral center at carbon 2, which is marked as (S). When the hydroxide ion (OH-) attacks the carbon adjacent to the chlorine atom, the chlorine leaves and a hydrogen from the adjacent carbon is also removed. The resulting product is (1S,2R,4S)-2-methyl-1-(propan-2-yl)cyclohexene.

It's important to note that the stereochemistry of the starting compound and the resulting product is represented by the (R) and (S) designations, indicating the arrangement of the substituents around the chiral carbon atoms.

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The standard cell potential (E°cell) of the reaction is found to be + 0.38 V, hence, option A is correct.

We will be usig the equation,

E°cell = (ΔG° / -nF) standard Gibbs free energy change is ΔG°, number of electrons transferred in the balanced equation is n, and Faraday constant (96,500 C/mol) is F. In the given reaction, 3 electrons are transferred, so n = 3.

Given ΔG° = -110 kJ/mol and F = 96,500 C/mol, we can substitute these values into the equation to calculate E°cell,

E°cell = (-110,000 J/mol / (-3 * 96,500 C/mol))

E°cell = 0.38 V

Therefore, the answer is, a. + 0.38 V

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Answer:

Becxause there is no whee5r else for the flame to go out fromk

Explanation:

NaCl

Na = 1

Cl=1

Answer:

19. because fire needs oxygen or air to keep the fire burning.

20.A molecule of sodium chloride, NaCl, consists of one atom each of sodium and chlorine. Hence, each molecule of NaCl has 2 atoms total. Similarly, we can calculate the total number of atoms in 1 mole of sodium chloride. Since 1 molecule contains 1 atom each of Na and Cl, 1 mole of NaCl will contain 1 mole each of Na and Cl.

Explanation:

Hope this helps!

The mass of the HCl that is required for the reaction is 2.92 g

The mass of the hydrogen gas produced is 0.08 g

Number of moles of the iron = 2.3 g/56 g/mol

= 0.04 moles

We have that 1 mole of the iron reacts with 2 moles of HCl

0.04 moles of iron would react with 0.04 * 2/1

= 0.08 moles

Mass of the HCl required = 0.08 moles * 36.5 g/mol

= 2.92 g

We have that the mole ratio of the iron and the hydrogen is 1:1 kit then follows that mass of the hydrogen produced would now be;

0.04 moles * 2 g/mol

= 0.08 g

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Answer:

Dilution is the process of decreasing the concentration of a solute in a solution, usually simply by mixing with more solvent like adding more water to the solution

Answer:

habitat destruction, overexploitation, climate change, nitrogen pollution, and invasive species.

Explanation:

Main Modern Causes of Extinction:

habitat destruction - the process by which a natural habitat becomes incapable of supporting its native species.

overexploitation - harvesting a renewable resource to the point of diminishing returns.

climate change - includes both global warmings driven by human emissions of greenhouse gases and the resulting large-scale shifts in weather patterns.

nitrogen pollution - a form of water pollution, refers to contamination by excessive inputs of nutrients.

invasive species - an introduced organism that negatively alters its new environment.

The different parts of the chemical equation below are identified as follows:

1. A: Solid

2. B: Liquid

3. C: Gas

4. D: Aqueous

5. (s): Solid

6. (l): Liquid

7. (g): Gas

A chemical equation is a symbolic representation of a chemical reaction where reactants are written on the left side and products on the right side. These reactants and products are identified with their respective states such as solid, liquid, gas, and aqueous.

The symbols for the physical states of the reactants and products are included in parentheses, alongside their respective chemical formulas.

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Answer:

4- radioactive isotopes

Explanation:

I don't remember exactly but this question was on the regents

Uranium-238  is a non- fissile element. It is a radioactive isotope that can be best used to determine geological formations. Thus, option 4 is correct.

Radioactive isotopes are elements that have an unstable atomic nucleus and can undergo radioactive decay to produce new particles and energy. They have the same atomic number as that of their parent species.

Isobars are a substance that has atomic mass and do not include uranium. Nuclear fusion and fission are the processes of nuclear energy that combine or splits the unstable nucleus to form a new particle.

Therefore, option 4. Uranium-238 is a radioactive isotope.

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Answer:

for the first one we need the previous question to be able to answer it. for the second one density and temperature

Explanation:

Answer:

It's 0.00015

Explanation:

got it right on edge 2021

Answer:

Q = 114349.5 J

Explanation:

Hello there!

In this case, since this a problem in which we need to calculate the total heat of the described process, it turns out convenient to calculate it in three steps; the first one, associated to the heating of the liquid water from 40 °C to 100 °C, next the vaporization of liquid water to steam at constant 100 °C and finally the heating of steam from 100 °C to 115 °C. In such a way, we calculate each heat as shown below:

[tex]Q_1=45g*4.18\frac{J}{g\°C}*(100\°C-40\°C)=11286J\\\\Q_2=45g* 2260 \frac{J}{g} =101700J\\\\Q_3=45*2.02\frac{J}{g\°C}*(115\°C-100\°C)=1363.5J[/tex]

Thus, the total energy turns out to be:

[tex]Q_T=11286J+101700J+1363.5J\\\\Q_T=114349.5J[/tex]

Best regards!

Answer:

To make glue. aaaaaaaaa

Answer:

Cleaning

Explanation:

Hydrochloric acid is an ingredient in household cleaners because it helps clean tough stains.

The most electrically conductive solution among the three given solutions is hydrobromic acid, which ionizes completely in the solution and produces a high amount of ions. Therefore, option (b) hydrobromic acid is the correct answer to this question.

Acids produce ions in solution, which leads to the solution being more conductive. The more ions an acid produces, the higher the electrical conductivity of the solution. Hence, to determine the electrical conductivity of the acid, we need to know the number of ions generated by the acid in the solution. Here, three acids: hydrobromic acid, acetic acid, and chloric acid have been taken at the same concentration. So, let's check the number of ions produced by each of the acids: Hydrobromic acid: It is a strong acid that dissociates completely in the aqueous solution.

The dissociation reaction is: HBr → H+ + Br−Since it ionizes completely in the solution, the electrical conductivity of the solution would be high. Acetic acid: It is a weak acid that dissociates partially in the aqueous solution. The dissociation reaction is: CH3COOH ↔ H+ + CH3COO−Since it does not ionize completely in the solution, the electrical conductivity of the solution would be low compared to hydrobromic acid. Chloric acid: It is a strong acid that dissociates completely in the aqueous solution. The dissociation reaction is: HClO3 → H+ + ClO3−Since it ionizes completely in the solution, the electrical conductivity of the solution would be high. So, the most electrically conductive solution among the three given solutions is hydrobromic acid, which ionizes completely in the solution and produces a high amount of ions. Therefore, option (b) hydrobromic acid is the correct answer to this question.

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Answer:

(A) 0.80 M

(B) 0.64 g

(C) 0.050 M

(D) 1.6 M

Explanation:

(A)

Convert 4.0 g to moles with molar mass. Convert 125 mL to L.

4.0 g x (1 mol/39.998 g) = 0.100 mol

125 mL x (1 L/1000 mL) = 0.125 L

Molarity = mol/L

Molarity = 0.100 mol/0.125 L = 0.80 M

(B)

Find moles of NaOH with the molarity you just found. And convert 20 mL to L.

Molarity = mol/L

0.80 M = mol/0.020 L

mol = 0.016

Convert moles to grams with molar mass.

0.016 mol x (39.998 g/1 mol) = 0.64 g

(C)

You know the molarity of a NaOH solution (Part A). 30 mL initial volume and 480 mL final volume are given. Dilution question so use the dilution formula.

M1V1 = M2V2

(0.80 M)(30 mL) = (M2)(480 mL)

M2 = 0.050 M

(D)

Dilution question again, use the dilution formula.

M1V1 = M2V2

(0.80 M)(200 mL) = (M2)(100 mL)

M2 = 1.6 M

Answer:

True

Explanation:

DON'T GIVE BRAINLIEST TO THE FILE EXPLOITER!!!!

You divide by the mass of the solution.

Percent by mass is the mass of the solute divided by the mass of the solution, multiplied by 100.

Example:

You dissolve a 4.00 g sugar cube in 350 mL of tea at 80 °C. The density of water at 80 °C is 0.975 g/mL. What is the percent by mass of sugar in the solution?

Solution

Step 1 — Determine mass of the solute.

The solute is the sugar cube. Mass of solute = 4.00 g.

Step 2 — Determine mass of solvent.

The solvent is the 80 °C water. Use the density of the water to find the mass.

mass of solvent = 350 mL ×

0.975

g

1

mL

= 341 g

Step 3— Determine the total mass of the solution

mass of solution = mass of solute + mass of solvent = 4.00 g + 341 g = 345 g

Step 4 — Determine percent composition by mass of the sugar solution.

% by mass =

mass of solute

mass of solution

× 100 % =

4.00

g

345

g

× 100 % = 1.159 %

The percent composition by mass of the sugar solution is 1.159 %.

Answer:

I think B

Explanation:

Red litmus paper is used more to find bases, blue litmus paper changes better when coming to find acids. So I believe it is B

The best approach best investigate whether substances are basic is to test each substance with red litmus paper.

Basic compounds are those which have a pH value in between the range of 7.1 to 14.

Red litmus paper changes its color from red to blue when comes in the contact of basic compounds. So to check the basicity of household substance we should use red litmus paper.

Hence test each substance with red litmus paper.

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By dividing the concentration of the reference solution by 100, you will obtain the concentration of the desired solution, which is 100 times less concentrated than the reference solution.

To find the concentration of a solution that is 100 times less than another solution, you can follow these steps:

1. Determine the concentration of the reference solution. Let's denote it as [A]₀.

2. Calculate the concentration of the desired solution. Let's denote it as [A].

3. Since the desired solution is 100 times less concentrated than the reference solution, you can divide the concentration of the reference solution by 100 to obtain the concentration of the desired solution:

  [A] = [A]₀ / 100

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Unicellular organisms such as amoeba and leishmania undergo binary fission.

Binary fission can be described as a form of asexual reproduction where an organism divides into two, each part having one copy of genetic material.

Binary fission can be described as a kind of asexual reproduction observed in prokaryotes and a few single-celled eukaryotes. In asexual reproduction, there is a separation of the parent cell into 2 new daughter cells. This process occurs with the division and duplication into two parts.

Binary fission is a primary of reproduction in prokaryotic organisms. Binary Fission happens without spindle apparatus formation in the cell.  The single DNA molecule starts replication and attaches each copy to parts of the cell membrane.

Prokaryotes and eukaryotes such as euglena reproduce via binary fission. This process is rapid, and its speed varies in species. The time needed by bacteria to double the cells it has is called known as doubling time.

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YESS It is true!!. In general, atoms are most stable, least reactive, when their outermost electron shell is full. Most of the elements important in biology need eight electrons in their outermost shell in order to be stable, and this rule of thumb is known as the octet rule.

Water evaporates more slowly than alcohol because water has more surface tension and more cohesive force than alcohol, So it takes more time for water to evaporate than for alcohol.

In alcohol, only O-H present is hydrophilic i.e. polar. Apart from this alcohol has a large hydrocarbon group i.e. C-H present in it, which is non-polar in nature. As a result, the attractive force between the atoms in alcohol is less. As a result, during boiling, the bonds between the atoms vibrate and break quickly. So alcohol evaporates faster.

In water, the entire molecule is polar. So there exists a strong attractive force between them. So the cohesive force is more in the case of water as compared to that of alcohol. As water is boiled the O-H bonds start to vibrate, since the bond is stronger, it requires higher energy for boiling. Thus it evaporates slower.

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The minimum hydroxide concentration required for the precipitation of [tex]Fe(OH)_2[/tex] to begin is [tex]1.691* 10^-^8 M.[/tex]

The balanced chemical equation for the precipitation reaction is:

[tex]Fe(OH)_2[/tex](s) ⇌ [tex]Fe^2^+[/tex](aq) + [tex]2OH^-[/tex](aq)

Ksp = [tex][Fe^2^+][OH^-]^2[/tex]

Ksp [tex]Fe(OH)_2[/tex] = [tex]4.87*10^-^1^7[/tex]

Ksp = [tex][Fe^2^+][OH^-]^2[/tex]

[tex]4.87*10^-^1^7[/tex] = (0.085)(2x)²

[tex]4.87*10^-^1^7[/tex] = 0.17x²

x² =[tex]4.87*10^-^1^7[/tex] / 0.17

x² = [tex]2.8647* 10^-^1^6[/tex]

x = [tex]1.691*10^-^8[/tex] M

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Answer:

The period number tells which is the highest energy level occupied by the electrons.

Explanation:

Answer:

CH4 and O2

Explanation:

The reactants of a chemical reaction are those that are on the left side of the chemical equation. In this case, methane (CH4) and oxygen (O2) which are on the left side, are the reactants.