What mass of steam initially at 120oC is needed to warm 200g of water in a glass container from 20.0 oC to 50.0 oC

Answer:

0.0900 mol/L

Explanation:

A chemist makes 330. mL of nickel(II) chloride working solution by adding distilled water to 220. mL of a 0.135 mol/L stock solution of nickel(II) chloride in water. Calculate the concentration of the chemist's working solution. Round your answer to significant digits.

Step 1: Given data

Step 2: Calculate the concentration of the final solution

We prepare a dilute solution from a concentrated one. We can calculate the concentration of the working solution using the dilution rule.

C₁ × V₁ = C₂ × V₂

C₂ = C₁ × V₁/V₂

C₂ = 0.135 mol/L × 220. mL/330. mL = 0.0900 mol/L

Answer: If matter goes through a chemical change then the physical properties are not likely to stay the same.

Explanation:

When chemical composition of a substance changes during a chemical reaction then it is called a chemical change.

Chemical change always leads to the formation of new substances. Properties like chemical reactivity, combustion, rusting etc are chemical changes.

For example, [tex]N_{2} + 3H_{2} \rightarrow 2NH_{3}[/tex]

Here, [tex]NH_{3}[/tex] will have different chemical as well as physical properties as compared to [tex]N_{2}[/tex] and [tex]H_{2}[/tex].

As physical properties are the properties that cause change in state of a substance.

Properties like boiling point, state of substance etc are physical properties.

Thus, we can conclude that if matter goes through a chemical change then the physical properties are not likely to stay the same.

Answer:

Explanation:

The structural formula of 2-methyl-3-hexene is drawn in the attached image below. After then, the three possible structures were drawn and the mechanism reaction.

From the mechanism shown, methanol deprotonates methoxide proton and neutralizes the positive charge to form methoxide. This is followed by the movement of electrons that takes place from the region of higher electron density to lower electron density.

Answer:

3.11 mol/kg

Explanation:

Molality M = number of moles of solute, n/mass of solvent, m

To calculate the number of moles of glycerol (C₃H₈O₃) in 22.75 g of glycerol, we find its molar (molecular) mass, M',

So, M' = 3 × atomic mass of carbon + 8 × atomic mass hydrogen + 3 × atomic mass of oxygen

= 3 × 12 g/mol + 8 × 1 g/mol + 3 × 16 g/mol = 36 g/mol + 8 g/mol + 48 g/mol = 92 g/mol.

So, number of moles of glycerol, n = m'/M' where m' = mass of glycerol = 22.75 g and M' = molecular mass of glycerol = 92 g/mol

So, n = m'/M'

n = 22.75 g/92 g/mol

n = 0.247 mol

So, the molality of the solution M = n/m

Since m = mass of ethanol = 79.6 g = 0.0796 kg, substituting the value of n into the equation, we have

M = 0.247 mol/0.0796 kg

M = 3.11 mol/kg

So, the molality of the solution is 3.11 mol/kg.

Answer: A mass of 0.518 g of phenol must be dissolved in 25.0 g of naphthalene to produce a solution that is 0.22 m in phenol.

Explanation:

Given: Mass of naphthalene = 25.0 g

Molality = 0.22 m

This means that 0.22 moles of solute is present per kg of solvent.

As 25.0 g  of naphthalene is there that will be 25.0 g per 1000 g (1 kg) is equal to 0.025 kg.

Hence, moles of phenol are calculated as follows.

[tex]Molality = \frac{moles}{mass (in kg)}\\0.22 m = \frac{moles}{0.025 kg}\\moles = 0.0055 mol[/tex]

Also, molar mass of phenol is 94.11 g/mol. This means that 1 mole of phenol contains 94.11 g.

Therefore, mass contained by 0.0055 moles of phenol is as follows.

[tex]0.0055 mol \times 94.11 g/mol \\= 0.518 g[/tex]

Thus, we can conclude that a mass of 0.518 g of phenol must be dissolved in 25.0 g of naphthalene to produce a solution that is 0.22 m in phenol.

Answer: There are [tex]1.23 \times 10^{22}[/tex] atoms present in 37.1 mg of tantalum.

Explanation:

Given: Mass of single tantalum atom = [tex]3.01 \times 10^{-22} g[/tex]

Mass of tantalum atoms = 37.1 mg (1 mg = 0.001 g) = 0.0371 g

Therefore, number of tantalum atoms present in 0.0371 grams is calculated as follows.

[tex]No. of atoms = \frac{0.0371 g}{3.01 \times 10^{-22}}\\= 1.23 \times 10^{20}[/tex]

Thus, we can conclude that there are [tex]1.23 \times 10^{22}[/tex] atoms present in 37.1 mg of tantalum.

There are [tex]1.23\times 10^{20}[/tex] atoms of tantalum in 37.1 mg of tantalum.

Explanation:

Given:

Mass of single atom of tantalum =[tex]3.01\times 10^{-22} g[/tex]

To find:

The number of atoms of tantalum in 37.1 milligrams.

Solution:

Mass of tantalum = 37.1 mg

[tex]1 mg = 0.001 g\\37.1 mg=37.1\times 0.001 g=0.0371 g[/tex]

The number of atoms in 0.0371 grams of tantalum = N

Mass of a single atom of tantalum = [tex]3.01\times 10^{-22} g[/tex]

Then a mass of N atoms of tantalum will be:

[tex]0.0371 g=N\times 3.01\times 10^{-22} g\\N=\frac{0.0371 g}{ 3.01\times 10^{-22} g}\\=1.23\times 10^{20}[/tex]

There are [tex]1.23\times 10^{20}[/tex] atoms of tantalum in 37.1 mg of tantalum.

Learn more about the unitary method here:

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Answer:

a. minus 10

Explanation:

An element in group 13 = Boron ,valence electrons = 3 , therefore, valence electrons in group 13 = group no. -10

An element in group 18 = Neon, valence electrons = 8 , therefore, valence electrons in group 18 = group no. - 10

For groups 13 through 18, the number of valence electrons in an atom is equal to the group number minus 10. Therefore, option (A) is correct.

Valence electrons in an atom can be described as the electrons occupying the outer most electron shell of an atom while the electrons in the inner shell are core electrons. Lewis structures can be helpful to calculate the number of valence electrons.

Valence electrons can be filled in several electron shells as they are caused interaction between atoms and responsible for the formation of chemical bonds. Only valence electrons can contribute to the formation of a chemical bond and decide the reactivity of the element.

The general electronic configuration of group 13 is ns²np¹ has three valence electrons. It can be determined as group number - 10 = 13 - 10 = 3.

The general electronic configuration of group 18 is ns²np⁶ has eight valence electrons. It can be determined as group number - 10 = 18 - 10 = 8.

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Answer:

a. 8.3= pKa of the aminoacid

b. Cysteine

Explanation:

The pH of an acid can be obtained using the H-H equation:

pH = pKa + log [A-] / [HA]

Where pH is the pH of the buffer = 7.0

pKa is the pka of the conjugate acid = ?

[A-] / [HA] is the ratio between conjugate base and conjugate acid. As the ratio of conjugate acid to conjugate base = 20:1, the [A-] / [HA] = 1/20

Replacing:

7 = pKa + log 1/20

7 = pKa - 1.30

7+1.30 = 8.3 = pKa of the aminoacid

The only aminoacid with a side chain with pKa = 8.3 is:

Cysteine. Allowing its identification.

Answer:

hope it helps much as you can

Answer:

the discovery will always need to be tested more where if you're investigating you should already be in a more controlled environment

The difference between accidental discoveries and scientific investigations are as follows.

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Answer:

the house found in a very cold are Igloos or the ice house

Answer:

The compound which doesn't contains ionic character is HC, H-atom and CL- atom shares 1 electron a to form covalent bond....

Answer:

light energy is converted to chemical energy during photosynthesis.

Explanation:

Law of conservation of energy says: Energy can neither be created nor destroyed-only converted from one form of energy to another.

Answer:

Answer:

For (1): The correct option is (a)

For (2): The correct option is (a) and 333.6 kJ of heat will be absorbed when 70.9 g of ammonia reacts.

Explanation:

There are 2 types of reactions that are classified based on enthalpy change:

Endothermic reactions: These are the reactions where heat is absorbed by the reaction. The change in enthalpy of the reaction, [tex]\Delta H_{rxn}[/tex] is positive for these reactions.

Exothermic reactions: These are the reactions where heat is released by the reaction. The change in enthalpy of the reaction, [tex]\Delta H_{rxn}[/tex] is negative for these reactions.

For the given chemical reaction:

[tex]2NH_3(g)\rightarrow N_2(g)+3H_2(g);Delta H=160kJ[/tex]

As the change in enthalpy or heat of the reaction is positive. Thus, the reaction is an endothermic reaction because heat is absorbed by the reaction.

When ammonia reacts, some amount of heat will be absorbed by the reaction. Thus, we can say the heat will be absorbed.

The number of moles is calculated by using the equation:

[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex] ......(1)

Given mass of ammonia = 70.9 g

Molar mass of ammonia = 17 g/mol

Using equation 1:

[tex]\text{Moles of ammonia}=\frac{70.9g}{17g/mol}=4.17mol[/tex]

By stoichiometry of the reaction:

If 2 mole of ammonia reacts, the heat absorbed is 160 kJ

So, if 4.17 moles of ammonia reacts, the heat absorbed will be = [tex]\frac{160kJ}{2mol}\times 4.17mol=333.6kJ[/tex]

Hence, 333.6 kJ of heat will be absorbed when 70.9 g of ammonia reacts

Answer:

pH=8.676

Explanation:

Given:

0.75 M [tex]NH_{3}[/tex]

0.20 M [tex]NH_{4}[/tex]

The objective is to calculate the pH of the buffer using the kb for [tex]NH_3[/tex]

Formula used:

[tex]pOH=pka+log\frac{[salt]}{[base]}\\[/tex]

pH=14-pOH

Solution:

On substituting salt=0.75 and base=0.20 in the formula

[tex]pOH=-log(1.77*10^{-5})+log\frac{0.75}{0.20}\\ =4.75+0.5740\\ =5.324[/tex]

pH=14-pOH

On substituting the pOH value in the above expression,

pH=14-5.324

Therefore,

pH=8.676

Answer: the answer is A

Explanation: add me hope i helped

Answer:

1 ) Δs ( entropy change for hot block ) = - Q / th  ( -ve shows heat lost to cold block )

Δs ( entropy change for cold block ) = Q / tc

∴ Total Δs = ΔSc + ΔSh

                 = Q/tc - Q/th

2) ΔSdecomposition = Δh / Temp = ( 181.6 * 10^3 / 773 ) = 234.928 J/k

Explanation:

1) To show that heat flows spontaneously from high temperature to low temperature

example :

Pick two(2) solid metal blocks with varying temperatures ( i.e. one solid block is hot and the other solid block is cold )

Place both blocks for time (t ) in an insulated system to reduce heat loss or gain to or from the environment

Check the temperature of both blocks after time ( t ) it will be observed that both blocks will have same temperature after time t ( first law of thermodynamics )

Δs ( entropy change for hot block ) = - Q / th  ( -ve shows heat lost to cold block )

Δs ( entropy change for cold block ) = Q / tc

∴ Total Δs = ΔSc + ΔSh

                 = Q/tc - Q/th

2) Entropy change for Decomposition of mercuric oxide

2HgO (s) → 2Hg(l) + O₂ (g)

Δs = positive

there is transition from solid to liquid and the melting point of mercury ( the point at which reaction will take place ) = 500⁰C

hence ΔSdecomposition = S⁻ Hg  -  S⁻ HgO =

Δh of reaction = 181.6 KJ

Temp = 500 + 273 = 773 k

hence ΔSdecomposition = Δh / Temp = ( 181.6 * 10^3 / 773 ) = 234.928 J/k

Answer: The balanced half-equations for silver + oxygen= silver oxide are:

Oxidation-half reaction: [tex]Ag \rightarrow 2Ag^{+} + 2e^{-}[/tex]

Reduction-half reaction: [tex]O_{2} + 2e^{-} \rightarrow 2O^{-}[/tex]

Explanation:

The word equation is as follows.

silver + oxygen = silver oxide

In terms of chemical formulas this equation can be written as follows.

[tex]Ag + O_{2} \rightarrow Ag_{2}O[/tex]

The removal on electron(s) from an atom, ion or molecule in a chemical reaction is called oxidation.

The gain of electron(s) by an atom, ion or molecule in a chemical reaction is called reduction.

Hence, half-reaction equations for the given reaction is as follows.

Oxidation-half reaction: [tex]Ag \rightarrow 2Ag^{+} + 2e^{-}[/tex]

Reduction-half reaction: [tex]O_{2} + 2e^{-} \rightarrow 2O^{-}[/tex]

As the number of atoms participating in the reaction are equal. Hence, the half-equations are balanced.

Thus, we can conclude that the balanced half-equations for silver + oxygen = silver oxide are:

Oxidation-half reaction: [tex]Ag \rightarrow 2Ag^{+} + 2e^{-}[/tex]

Reduction-half reaction: [tex]O_{2} + 2e^{-} \rightarrow 2O^{-}[/tex]

Answer:

It predicts whether or not a reaction will be spontaneous.

Explanation:

The equation;

∆G= ∆H - T∆S enables us to obtain the Gibbs free energy of a chemical process.

The Gibbs free energy value tells us whether a chemical process will be spontaneous or not.

When;

∆G>0 the reaction is not spontaneous

∆G=0 the reaction is at equilibrium

∆G<0 the reaction is spontaneous

Answer:

To transfer leftover solids to the filtration funnel and wash out crystals after recrystallization, ice cold methanol should be used (the mother liquor used for recrystallization).

Explanation:

Hope this helped

Answer:

Ka = 3.45x10⁻⁶

Explanation:

First we calculate [H⁺], using the given pH:

To solve this problem we can use the following formula describing a monoprotic weak acid:

We input the data that we already know:

And solve for Ka:

One of the lab safety rules being violated is that Jodi doesn't have her hair tied up. She should have her hair tied up. Having her long hair not tied up or away from her face is a safety hazard. Jodi is also not wearing glasses, which is essential when working with chemicals. One of the Bunsen Burners aren't being used but it's on, which is a fire hazard.

Answer:

Jodi should wear her hair up to avoid a mishap, such as lighting her hair on fire. Then, instead of using a fire extinguisher on Jodi, Kimberly should use a fire blanket to prevent additional damage. Mac is preoccupied with a second flame and maybe Jodi without her safety goggles?

Answer:

Active transport by the Na+-K+ pump

Explanation:

Active transport by the Na+-K+ pump

Maintenance (and restoration) of the resting ion concentrations depends on the Na+-K+ pump. Once gated ion channels are closed, the combined action of the pump and ion leakage (particularly that of K+) establishes a resting membrane potential in a typical neuron of around âˆ'70 mV.

Answer:

H2

Explanation:

Answer:

[tex]{ \bf{H _{2} }} \\ { \tt{hydrogen \: gas}}[/tex]

Explanation: The hypothesis is a prediction, but it involves more than a guess. Most of the time, the hypothesis begins with a question which is then explored through background research. It is only at this point that researchers begin to develop a testable hypothesis.

(Unless you are creating an exploratory study, your hypothesis should always explain what you expect to happen)

Answer:

There will be very little of BrOCl BrCl

Explanation:

Based on the equilibrium:

Br2(g) + OCl2(g) ⇄ BrOCl(g) + BrCl(g)

The equilibrium constant, Kc, is:

Kc = 1.58x10⁻⁵ = [BrOCl] [BrCl] / [Br2] [OCl2]

As Kc is <<< 1, in equilibrium, the concentration of products will remain lower regard to the concentration of the reactants. That means, right answer is;

Answer:

methylcyclohexane does not possess a chiral center

Explanation:

A molecule is said to possess a chiral center if one or more of the atoms in the molecule is bonded to four different atoms or groups.

If we look at methylcyclohexane, none of the carbon atoms in the molecule is bonded to four different atoms or groups hence the molecule contains no chiral centers and will not exhibit optical isomerism.

So, methylcyclohexane has a plane of symmetry thus it is an achiral molecule.