How we get this answer?? I need the way with rules?​

Answer:

We know that the specific heat of water is:

c = 1cal/g*°C

This means, that we need 1 cal to increase the temperature of 1 gram of water by 1°C

Here, we increased the temperature of 50.1g of water by 12°C

Then the number of calories needed to do this is given by:

x = (mass of water in grams)*(how much increased the temp in °C)*1cal/g*°C

x = (50.1g*12°C)*1cal/g*°C = 601.2 cal

But we want this in Kcal, remember that:

1Kcal = 1000cal

Then:

601.2 cal = (601.2/1000) Kcal = 0.6012 Kcal

Now, for the cracker part, the energy was released by the amount of cracker that was burned.

The original mass was 2.4g

the final mass ios 1.3g

the difference is:

2.4g - 1.3g = 1.1g

This means that 1.1g was the burned mass.

The number of kilocalories of heat per gram released by the cracker is just:

n = (0.6012 Kcal)/(1.1 g) = 0.547 Kcal/g

0.547 kilocalories per gram.

Answer:

d. Mixing helps ensure that the measured pH is reflective of the entire solution.

Explanation:

Hello there!

In this case, according to the given information, it turns out possible for us to reason that the answer is d. Mixing helps ensure that the measured pH is reflective of the entire solution because mixing help us to move the ions all around the solution so it undergoes homogenization and the measured pH at any point of the solution will be the same.

Moreover, we need to keep in mind that the incomplete stirring leads to regions with more concentration of the acid or base, or what we know as a gradient of concentration, which may lead to a incorrect measurement.

Regards!

Answer:

The molality of solution=12.605 m

Explanation:

We are given that

Molar mass of Hydrogen peroxide, M=34 g/mol

Density of solution, [tex]\rho=1.11gcm^{-3}[/tex]

30% Means mass of solute (Hydrogen peroxide)=30 g

Mass of solvent =100-30=70 g

Total mass of solution, m=100 g

Number of moles of solute=[tex]\frac{given\;mass}{molar\;mass}[/tex]

Using the formula

Number of moles of hydrogen peroxide=[tex]\frac{30}{34}[/tex]

Now, molality of solution

[tex]m=\frac{number\;of\;moles\;of\;solute}{mass\;of\;solvent}\times 1000[/tex]

[tex]m=\frac{30}{70\times 34}\times 1000[/tex]

[tex]m=12.605 m[/tex]

Hence, the molality of solution=12.605 m

Answer:

a table of the chemical elements arranged in order of atomic number, usually in rows, so that elements with similar atomic structure (and hence similar chemical properties) appear in vertical columns.

Answer:

The  predominant intermolecular force in the liquid state of each of these compounds:

ammonia (NH3)

methane (CH4)

and nitrogen trifluoride (NF3)

Explanation:

The types of intermolecular forces:

1.Hydrogen bonding: It is a weak electrostatic force of attraction that exists between the hydrogen atom and a highly electronegative atom like N,O,F.

2.Dipole-dipole interactions: They exist between the oppositely charged dipoles in a polar covalent molecule.

3. London dispersion forces exist between all the atoms and molecules.

NH3 ammonia consists of intermolecular H-bonding.

Methane has London dispersion forces.

Because both carbon and hydrogen has almost similar electronegativity values.

NF3 has dipole-dipole interactions due to the electronegativity variations between nitrogen and fluorine.

Answer:

pH= 1.9 then [tex]H_{3} PO_{4}[/tex]

pH = 5.0 , [tex]CH_{3} COOH[/tex]

pH = 3.9 , HCOOH

As we know range left [tex]pH= pKa+/- 1[/tex]

Answer: Chemicals like acids and bases are harmful and must be neutralized before draining.

Explanation:

A strong acid or strong base is required to be diluted or neutralized before it is discarded in the drain as if is discarded without diluting and neutralization it can spill and splash from sink or drain and can harm people in chemistry lab, moreover the fumes of the discarded chemical on spilling can cause respiratory tract burning and can even cause fire hazard so it must be converted into less harmful form and then must be drained.  

Answer:

0 J

Explanation:

Applying,

ΔE = q+w................ Equation 1

Where ΔE = change in internal energy of the system, q = Heat of the system, w = work of the system.

Note: q is positive, while w is negative

From the question,

Given: q = 425 J, w = -425 J

Substitute these values into equation 1

ΔE = 425-425

ΔE = 0 J

Hence the change in internal energy of the system is 0 J

Answer:

Hence the concentration of a MnO41- solution that has absorbance of 0.490 in the same cell at that wavelength is 0.3266.

Explanation:

Now A = el, el=const

Then,

[tex]A2 / A1 = C2/ C1\\\\0.49/ 0.48 = C2 / 0.32\\\\C2 = 0.3266[/tex]

Answer:

+ axit

CH2=CH-CH2-COOH,

CH3-CH=CH-COOH (tính cả đồng phân hình học)

CH2=C(CH3)-COOH.

+ este

HCOOCH=CH-CH3 (tính cả đồng phân hình học)

HCOO-CH2-CH=CH2,

HCOOC(CH3)=CH2.

CH3COOCH=CH2

CH2=CH-COOCH3

Answer:

0.17 g

Explanation:

Since the volume of gas collected is 132 mL, we need to find the number of moles of gas present in 132 mL.

So, number of moles, n = volume of gas, v/molar volume, V

n = v/V where v = 132 mL = 0.132 L and V = 22.4 L

So, substituting the values of the variables into the equation, we have

n = v/V

n = 0.132 L/22.4 L

n = 0.005893 mol

We then need to calculate the molar mass of CO, M = atomic mass of carbon + atomic mass of oxygen = 12 g/mol + 16 g/mol = 28 g/mol

Also, number of moles of gas, n = m/M where m = mass of CO and M = molar mass of CO

m = nM

m = 0.005893 mol × 28 g/mol

m = 0.165004 g

m ≅ 0.17 g to 2 significant digits

Answer:

A speed lathe is a type of lathe that is designed to operate much faster than its common counterpart.

Explanation:

Given set of elements in one column and their classification in another column.

1. Phosporus                         c.Metallic lattice

2. Bromine                           d.Covalent network.

3. Hydrogen                          b. Molecules

4. Krypton                              a. Discrete atoms

Since Krypton is an inert gas and it exists in discrete atoms.

Hydrogen exists as a diatomic gas.

Bromine exists as Br_2 liquid and is held by covalent bonds.

Phosphorus exists as P_4 molecules and it exits as a metallic lattice.

Answer:

Physical

Chemical

Explanation:

Intermolecular forces are the forces that hold the molecules of a substance together in a particular state of matter. They decide the physical properties of a substance.

The intra molecular forces are the bond forces that hold atoms together in molecules. The nature of this bonding determines the chemical properties of substances.

Answer:

density of second liquid = 650 kg/m³

Explanation:

Given that:

The volume of the plastic block submerged inside the water  = 0.5 V

The force on the plastic block  = [tex]\rho_1V_1g[/tex]

[tex]= 0.5p_1 V_g[/tex]

when the block is floating, the weight supporting the force (buoyancy force) is:

W [tex]= 0.5p_1 V_g[/tex]

[tex]\rho Vg = 0.5p_1 V_g[/tex]

[tex]\rho = 0.5 \rho _1[/tex]

where;

water density [tex]\rho _1[/tex] = 1000

[tex]\rho = 0.5 (1000)[/tex]

[tex]\rho = 500 kg/m^3[/tex]

In the second liquid, the volume of plastic block in the water = (100-23)%

= 77% = 0.7 V

The force on the plastic block is:

[tex]= 0.77p_2 V_g[/tex]

when the block is floating, the weight supporting the force (buoyancy force) is:

[tex]W = 0.77p_2 V_g[/tex]

[tex]\rho Vg = 0.77 \rho_2 V_g \\ \\ \rho = 0.77 \rho_2 \\ \\ 500 = 0.77 \rho_2 \\ \\ \rho_2 = 500/0.77[/tex]

[tex]\mathbf{ \rho_2 \simeq 650 \ kg/m^3}[/tex]

Answer:

[tex]H_2CO_3(aq)+2OH^-(aq)\rightarrow (CO_3)^{2-}(aq)+2H_2O(l)[/tex]

Explanation:

Hello there!

In this case, according to the given information, it turns out possible for us to set up this net ionic equation, by firstly setting up the complete molecular equation as follows:

[tex]H_2CO_3(aq)+2NaOH(aq)\rightarrow Na_2CO_3(aq)+2H_2O(l)[/tex]

Thus, since carbonic acid is weak it merely ionizes whereas sodium hydroxides ionizes for the 100 % as it is strong; thus, we can write the complete ionic equation:

[tex]H_2CO_3(aq)+2Na^+(aq)+2OH^-(aq)\rightarrow 2Na^+(aq)+(CO_3)^{2-}(aq)+2H_2O(l)[/tex]

Whereas sodium ions act as the spectator ones to be cancelled out for us to obtain:

[tex]H_2CO_3(aq)+2OH^-(aq)\rightarrow (CO_3)^{2-}(aq)+2H_2O(l)[/tex]

Regards!

Answer:

41 g

Explanation:

The equation of the reaction is;

Cr(NO3)3(aq)+Na3PO4(aq)=3NaNO3(s)+CrPO4(aq)

Number of moles of chromium nitrate = 37g/ 146.97 g/mol = 0.25 moles

1 mole of sodium phosphate reacts with 1 mole of chromium nitrate

x moles of sodium phosphate react as with 0.25 moles of chromium nitrate

x= 1 × 0.25/1

x= 0.25 moles

Mass of sodium phosphate = 0.25 moles × 163.94 g/mol

Mass of sodium phosphate = 41 g

endothermic absorbs heat

exothermic gives heat

a. endothermic

b. exothermic

c. endothermic

d. exothermic

a. Ice melting - endothermic

b. Water condensing on the surface - exothermic

c. Baking a cake - endothermic

d. The chemical reaction inside an instant cold pack - endothermic

e. A car using gasoline - exothermic

An exothermic reaction can be described as a thermodynamic chemical reaction that emits energy from the system to its surroundings usually in the form of light, heat, or sound.

While an endothermic reaction can be described as an opposite of an exothermic reaction where the energy gains in the form of heat. In exothermic chemical reactions, the bond energy is transformed into thermal energy.

In exothermic reactions, the reaction happens the form of the kinetic energy of molecules when the energy is released. The release of energy is due to the electronic transition of electrons from one energy level to another.

The burning of gasoline, and water condensation is also an exothermic reaction in which energy is released while ice melting and baking cake is an endothermic reaction.

Learn more about the exothermic process, here:

brainly.com/question/12321421

#SPJ5

Answer:

2.25g of NaF are needed to prepare the buffer of pH = 3.2

Explanation:

The mixture of a weak acid (HF) with its conjugate base (NaF), produce a buffer. To find the pH of a buffer we must use H-H equation:

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

Where pH is the pH of the buffer that you want = 3.2, pKa is the pKa of HF = 3.17, and [] could be taken as the moles of A-, the conjugate base (NaF) and the weak acid, HA, (HF).

The moles of HF are:

500mL = 0.500L * (0.100mol/L) = 0.0500 moles HF

Replacing:

3.2 = 3.17 + log [A-] / [0.0500moles]

0.03 = log [A-] / [0.0500moles]

1.017152 = [A-] / [0.0500moles]

[A-] = 0.0500mol * 1.017152

[A-] = 0.0536 moles NaF

The mass could be obtained using the molar mass of NaF (41.99g/mol):

0.0536 moles NaF * (41.99g/mol) =

Answer:

(A) Slipping and breaking

(B) Clean and dry

(C) Cracks

Explanation:

This describes the process of unpacking a glassware for use.

You should set out support like a cork ring or clamp (these are simple machines that'll hold the glassware in place) before removing the glassware from a glassware kit; to place the glassware in and to stop it from slipping and breaking.

Thoroughly check that the glassware is clean and dry and that it does not have any cracks, before using it.

Answer:

See explanation

Explanation:

The molecule IF5 possesses five I-F polar bonds. However, the presence of polar bonds does not automatically imply that the molecule will be polar.

The geometry of the molecule is very important in determining the polarity of a compound. Since IF5 has a lone pair of electrons, the molecule is bent and as such there is a permanent dipole moment created in the molecule thereby making IF5 polar in nature.

Answer:

Option C

Explanation:

From the question we are told that:

Difference in energy [tex]\delta E =3.49 * 10^{-17} J[/tex]

The Ground state Difference in energy at n=1

[tex]\delta E_g = 2.18 * 10^{-18} × Z^2[/tex]

Generally the equation for Difference in energy is mathematically given by

[tex]\delta E=\delta E_g[/tex]

Therefore

[tex]3.49 * 10^{-17} = 2.18 * 10^{-18} * Z^2[/tex]

[tex]Z^2=16[/tex]

[tex]Z=4[/tex]

Therefore

Charge on element Z Q_Z

[tex]Q_Z= Atomic\ no\. of\ element - No.\ of\ electrons\ of\ element[/tex]

[tex]Q_Z =4-1[/tex]

[tex]Q_Z=+3[/tex]

Option C

Answer:

a. 2..86 b. 4.86 c. 10.7 d. 8.7

Explanation:

a. Determine a pH at which 50% of ClCH2COOH will be in a form that possesses a charge.

Using the Henderson-Hasselbalch equation,

pH = pKa + log[A⁻]/[HA]

where [A⁻] = concentration of conjugate base (or charged form) and [HA] = concentration of acid.

At 50% concentration, [A⁻] = [HA] ⇒ [A⁻]/[HA] = 1

So, pH = pKa + log[A⁻]/[HA]

pH = pKa + log1

pH = pKa = 2.86

b. Determine a pH at which pH more than 99% of ClCH2COOH will be in a form that possesses a charge.

Let x be the concentration of the acid. Since 99% of it should possess a charge, the basic concentration is 0.99x while the acidic concentration is remaining 1 % (1 - 0.99)x = 0.01x

Using the Henderson-Hasselbalch equation,

pH = pKa + log[A⁻]/[HA] where [A⁻] = concentration of conjugate base (or charged form) = 0.99x and [HA] = concentration of acid = 0.01x.

pH = pKa + log0.99x/0.01x

pH = pKa + log0.99/0.01

pH = 2.86 + log99

pH = 2.86 + 1.996

pH = 4.856

pH ≅ 4.86

c. Determine a pH at which 50% of CH3CH2NH+3 will be in a form that possesses a charge.

Using the Henderson-Hasselbalch equation,

pH = pKa + log[A⁻]/[HA]

where [A⁻] = concentration of conjugate base and [HA] = concentration of acid.

At 50% concentration, [A⁻] = [HA] ⇒ [A⁻]/[HA] = 1

So, pH = pKa + log[A⁻]/[HA]

pH = pKa + log1

pH = pKa = 10.7

d. Determine a pH at which pH more than 99% of CH3CH2NH+3 will be in a form that possesses a charge.

Let x be the concentration of the acid. Since 99% of it should possess a charge, the basic concentration is 0.01x while the acidic concentration is remaining 99 % (1 - 0.01)x = 0.99x (which possesses the charge).

Using the Henderson-Hasselbalch equation,

pH = pKa + log[A⁻]/[HA] where [A⁻] = concentration of conjugate base = 0.01x and [HA] = concentration of acid = 0.99x.

pH = pKa + log0.01x/0.99x

pH = pKa + log1/99

pH = 10.7 - log99

pH = 10.7 - 1.996

pH = 8.704

pH ≅ 8.7

Answer:

56511.75 J

13506.3 Calories

Explanation:

Applying,

Q = cm(t₂-t₁).................. Equation 1

Where Q = amount of heat, m = mass of the iron, c = specific heat capacity of the iron, t₁ = initial temperature, t₂ = final temperature.

From the question,

Given: m = 75 g, c = 0.499 J/g.°C, t₂ = 1535°C, t₁ = 25°C

Substitute these values into equation 1

Q = 75(0.499)(1535-25)

Q = 75(0.499)(1510)

Q = 56511.75 J

Q in Calories is

Q = (56511.75×0.239)

Q = 13506.3 Calories

Answer:

O2(g) + 2H2O(l) --------> 2H2O2(aq) + 2e

Explanation:

An oxidation reaction reaction refers to a reaction in which electrons are lost. In this case, we are about to see the full balanced half-reaction for the oxidation of liquid water to aqueous hydrogen peroxide in basic aqueous solution.

The full equation is;

O2(g) + 2H2O(l) --------> 2H2O2(aq) + 2e

So, two electrons were lost in the process.

Answer:

3.00 L

Explanation:

P₁V₁ = P₂V₂

V₁ = 1.00 L

P₁ = (x) atm

P₂ = [tex]\frac{1}{3}[/tex] · (P₁) = [tex]\frac{x}{3}[/tex]

V₂ = unknown

(x atm)(1.00 L) = ( [tex]\frac{x}{3}[/tex] atm)(V₂)

divide both sides by ( [tex]\frac{x}{3}[/tex] atm)

( 1.00x )( [tex]\frac{3}{x}[/tex] ) = V₂

x cancels out

(1.00)(3) = V₂

V₂ = 3.00 L