How many molecules are present in one mole of oxygen?

Answer:

If the weight of chemical is same so it represent that the experiment is valid.

Explanation:

If Bronwyn performed the same chemical reaction four times and she measure the weight of chemical with the help of electrical weight balance so if she find out the weight of the chemical that is produced during four experiments then we can say that the experiment is valid because the experiment was performed four times and that is enough for validation of the experiment.

Answer:

The correct option is;

D. Petrol  > Alcohol > Kerosene oil > Water

Explanation:

The volatility of a liquid is a measure of how readily it evaporates or vaporizes such that a volatile liquid will evaporate and be present as a vapor at a given temperature or pressure than a less volatile liquid

The volatility of a liquid is directly related to the liquid's vapor pressure such that the higher the vapor the more volatile the liquid

The Reid vapor pressures of the given liquids are as follows;

Alcohol (Ethanol)= 17-55 kPa

Petrol = 53-60 kPa

Kerosene Oil= 6.8 kPa

The vapor pressure for water at 37.8°C = 6.6 kPa

Therefore, the correct order evaporation is as follows, starting from the highest vapor pressure to the lowest;

Petrol  > Alcohol >  Kerosene Oil > Water.

Answer:

6.022 x 10^23 molecules

Explanation:

Answer:

Carbon is the only element having the ability to form large numbers of compounds because carbon atom has four electrons in its valence shell and can share not only one but more electrons with other atoms and can form four chemical bonds  which results into huge number of hydrocarbons.

Different types of hydrocarbons are:

Methane - it has only one carbon bounded with four hydrogen atoms with single bond and have chemical formula CH4.

Ethane: it has two carbon atoms attached with single bond and bounded with three hydrogen atoms each with single bond and have chemical formula C2H6.

Ethene: it has two carbon atoms attached with double bond and bounded with two hydrogen atoms each with single bond and have chemical formula C2H4.

Butyne: it has four carbon atoms, two of which are attached with triple bond and rest electrons are attached with hydrogen atoms and have chemical formula C4H6.

Hence, carbon  is able to form such a large number of compounds.

Answer:

b) Inductive Reasoning

Explanation:

Answer:  B. 1.58 x 10 ∧ -10 mol/dm3 of OH- ions

Explanation:

pOH = - log [OH-]

It is well known that; pH + pOH = 14

That is to say; 4.2 + pOH = 14, therefore; pOH = 14 - 4.2 = 9.8

9.8  = - log [OH-]

In other to get the concentration, we take the anti-log of 9.8 .

Anti-log of 9.8 = 1.58 x 10 ∧ -10mol/dm3.

Answer: B

Explanation:

To find the amount of heat required, you would use q=mcΔT.

[tex]q=2g(4.18J/g°C)(68-34°C)[/tex]

q=284.2 J

*Please ignore the capital A in the equation. I can't find a way to type in the degree sign into the equation without the A appearing.

Answer:

Explanation:

According to hooks law "provide the elastic limit of an elastic material is not exceeded the extension e is directly proportional to the applied force F"

[tex]F= ke[/tex]

where F= applied force

           k= spring constant

           e= extension

Given data

length of string l = 16cm

extension  e = 20-16= 4cm

applied force = 5N

we need t o first calculate the spring constant k

apply the formula

[tex]F= ke[/tex]

[tex]5=k*4\\k= \frac{5}{4} \\k= 1.25N/cm[/tex]

we can now calculate the extension of the string when supporting a 6N weight

[tex]F= ke\\6=1.25*e\\e= \frac{6}{1.25} \\e= 4.8cm[/tex]

The length of the string when supporting a 6N weight is

[tex]= length+ extension\\= 16+4.8\\= 20.8cm[/tex]

COMMENT :According to the analysis an extra  weight of 1N will cause add 0.8cm to the length of the string

Answer:

Approximately [tex]0.20\; \rm L[/tex].

Explanation:

Convert the temperature of this gas to absolute temperature:

[tex]T = 25\; \rm ^\circ C \approx (25 + 273.15)\; \rm K = 298.15\; \rm K[/tex].

Let [tex]P[/tex] and [tex]V[/tex] represent the pressure and volume of this gas, respectively. Let [tex]n[/tex] represent the number of gas particles in this gas. Let [tex]R[/tex] represent the ideal gas constant. By the ideal gas law:

[tex]P \cdot V = n \cdot R \cdot T[/tex].

For this question:

Look up the ideal gas constant [tex]R[/tex] that takes [tex]\rm atm[/tex] as the unit for pressure:

[tex]R \approx 0.082057\; \rm L \cdot atm \cdot K^{-1}\cdot mol^{-1}[/tex].

This question is asking for [tex]V[/tex], the volume of this gas. Rearrange the ideal gas equation and solve for [tex]V[/tex]:

[tex]\begin{aligned} V &= \frac{n \cdot R \cdot T}{P} \\ &\approx \frac{0.00831\; \rm mol\times 0.0082057\; \rm L \cdot atm \cdot K^{-1}\cdot mol^{-1}\cdot 298.15\; \rm K}{1.01\; \rm atm} \\ &\approx 0.0020\; \rm L\end{aligned}[/tex].

Answer:

The new temperature is 527.15 ºC.

Explanation:

Charles’s law states that the volume of a fixed  amount of gas maintained at constant pressure is directly proportional to the absolute  temperature of the gas (the absolute temperature is the Kelvin temperature).

We need to calculate the temperature after the expansion, that is T₂. For that, we use Charles' law:

[tex] V₁ ÷ T₁ = V₂ ÷ T₂ [/tex]

Because we have to use the absolute temperature, we convert ºC to K adding 273.15:

T₁ = 127 ºC + 273.15 ºC = 400.15 K

[tex] T₂ = V₂ × T₁ ÷ V₁ [/tex]

[tex] T₂ = 20. 0 L × 400.15 K ÷ 10.0 L [/tex]

T₂ = 800.3 K

We substract 273.15 to the result to convert it back to ºC:

T₂ = 800.3 - 273.15  = 527.15 ºC.

Answer:

THE FREEZING POINT OF A WATER SOLUTION OF FRUCTOSE MADE BY DISSOLVING 92 g OF FRUCTOSE IN 202g OF WATER IS -4.70 ◦C

Explanation:

To calculate the freezing point of a water solution of fructose,

1. calculate the molar mass of Fructose

( 12 * 6 + 1*12 + 16*6) =72 + 12 +96 = 180 g/mol

2. calculate the number of moles of fructose in the solution

number of moles = mass / molar mass

n = 92 g / 180 g/mol

n = 0.511 moles.

3. calculate the molarity of the solution

molarity = moles / mass of water in kg

molarity = 0.5111 / 202 g /1000 g

molarity = 0.5111 / 0.202

molarity = 2.529 M

4. calculate the change in the freezing point of pure solvent and solution ΔTf

ΔTf = Kf * molarity of the solute

Kf = 1.86 ◦C/m for water

ΔTf = 1.86 * 2.529

ΔTf = 4.70 C

5. the freezing point is therefore

0.00 ◦C - 4.70 ◦C = -4.70 ◦C

Answer:

-4.7°C

Explanation:

In this question, we want to calculate the freezing point of the water solution of fructose.

We proceed as follows;

Firstly, we find the number of moles of the fructose using molar mass

Number of moles = mass/molar mass

mass is 92g , molar mass of fructose is 180g/mol

Number of moles = 92/180 = 0.51 moles

Next thing is to calculate the molality of the solution = number of moles of fructose/mass of water in kg = 0.51/(202/1000) = 0.51/0.202 = 2.525m

Now, we calculate the freezing point depression;

Δ[tex]T_{f}[/tex] = [tex]K_{f}[/tex] × m

where [tex]K_{f}[/tex] refers to the molal freezing point depression of the solvent = 1.86

Δ[tex]T_{f}[/tex] = 1.86 × 2.525 = 4.7 °C

Since the presence of impurities decrease freezing point and the normal freezing point of water is 0 °C, the freezing point of the solution is 0-4.7 = -4.7 °C

Answer:

The answer is A.

Explanation:

When acid react with metal carbonate, it will form salt, water and carbon dioxide.

For example :

HCl + CaCO3 → CaCl + H2O + CO2

Answer:

Melting point

Explanation:

Answer:

Melting point

Explanation:

When a solid turns into a liquid, it is melting.  Therefore, it is the melting point.

Answer:

2 moles of sugar in 1,000g of water

Answer:

737.52 mL de agua

Explanation:

En este caso solo debes usar la expresión de molaridad de una solución la cual es:

M = moles / V

Donde:

V: Volumen de solución.

Como queremos saber la cantidad de agua, queremos saber en otras palabras cual es la cantidad de solvente que se utilizó para preparar los 800 mL de disolución.

Una disolución se prepara con un soluto y solvente. El soluto lo tenemos, que es el nitrato de plata. Con la expresión de arriba, calculamos los moles de soluto, y luego su masa. Posteriormente, calculamos el volumen con la densidad, y finalmente podremos calcular el solvente de esta forma:

V ste = Vsol - Vsto

Primero calcularemos los moles de soluto:

moles = M * V

moles = 2 * 0.800 = 1.6 moles

Con estos moles, se calcula la masa usando el peso molecular reportado que es 169.87 g/mol:

m = moles * PM

m = 1.6 * 169.87 = 271.792 g

Ahora usando el valor de la densidad, calcularemos el volumen de soluto empleado:

d = m/V

V = m/d

V = 271.792 / 4.35

V = 62.48 mL

Finalmente, la cantidad de agua necesaria es:

V agua = 800 - 62.48

V agua = 737.52 mL

Answer: thermal equilibrium

Explanation: the temperature increased only when all of the water was in one phase.

Answer:

iron

Explanation:

rust is an oxide of iron

Answer:

Explanation:

The innate immune system is a defense system with which we are all born and which protects us at all times against all antigens, prevents harmful external bodies from entering our body.

The acquired immune system is the second line of defense and develops by exposing itself to various antigens, building a defense against it when the innate system cannot fight the invader.

Answer:

Part A. The Innate immune system

Part B. The adaptive (or active) immune system

Explanation:

The immune system refers to the organs, tissues cells and proteins which work together to protect the body from harmful invaders that cause disease such as micro-organisms like viruses, bacteria, etc.

Organs and tissues that form part of the immune system include the thymus and bone marrow, lymph nodes and vessels, spleen, and skin.

The main immune cells are the white blood cells, also called leukocytes. Some types of white blood cells, called phagocytes engulf invading organisms. Others called lymphocytes  help the body remember the invaders and destroy them.  The two kinds of lymphocytes are B lymphocytes and T lymphocytes, whose name depend on where they mature. Lymphocytes start their life in the bone marrow and either stay there and mature into B cells, or go to the thymus gland to mature into T cells.

The immune system consists of two main parts or system.

Answer:

The combustion will release -3,321 KJ/mol of energy

Explanation:

What we need to do here is to first calculate the number of moles of methane burnt.

Mathematically, the number of moles of methane burnt = mass of methane/molar mass of methane

Molar mass of methane = 16g /mol

Thus the

number of moles will be ;

59.7/16 = 3.73 moles

Now, 1 mole of methane produces -890 KJ/mol if energy

Then the energy produced by by 3.73 moles of methane would be 3.73 * 890 = -3,320.8125

which is approximately -3,321 KJ/mol

Kindly note that the amount of heat is negative because it is an exothermic reaction

Answer:

the answer to this question is hydrogen gas

Answer : The correct option is, (C) 3

Explanation :

Lewis-dot structure : It shows the bonding between the atoms of a molecule and it also shows the unpaired electrons present in the molecule.

In the Lewis-dot structure the valance electrons are shown by 'dot'.

The given molecule is, [tex]CH_3Cl[/tex]

As we know that carbon has '4' valence electrons, hydrogen has '1' valence electron and chlorine has '7' valence electrons.

Therefore, the total number of valence electrons in [tex]CH_3Cl[/tex] = 4 + 3(1) + 7 = 14

According to Lewis-dot structure, there are 8 number of bonding electrons and 6 number of non-bonding electrons.

Hence, the number of lone pairs of electrons present on chlorine are, 3.

Answer:

Mass and charge is conserved

Explanation:

According to the law of conservation of mass, matter is neither created or destroyed. With the exception of nuclear reactions where mass is converted to energy thereby leading to an apparent loss in mass, this law applies to chemical reactions.

A redox reaction is a type of chemical reaction which involves a transfer of electrons. In a redox reaction, the mass of reactant particles is conserved. Also, as electrons are transferred between atoms, one donates and the other accepts. The charge of atoms depends on this gain or loss of electrons. A gain of electrons reduced the charge of an atom whereas a loss of electrons increases the charge. This two processes occur concurrently, therefore, charge is also conserved.

Answer:

-the number of outer electrons

Explanation:

Outer electrons are referred to as valence electrons and they are typically what determines the property of an elements such as their reactivity.

For eg, Na (sodium) has 1 valence electron and it really wants to give it aways so it can return back to octet rule (having 8 electrons in outershell) to become stable. So when you put sodium in water (you can watch videos of it) it literally blows because of high reactivity.

Answer: C

Explanation:

For this problem, we would use Charles's Law. We fill in what we are given and solve.

Charles's Law: [tex]\frac{V_{1} }{T_{1} } =\frac{V_{2} }{T_{2} }[/tex]

[tex]\frac{10 L}{5K} =\frac{4.00L}{T_{2} }[/tex]

[tex]10T_{2}= 20[/tex]

[tex]T_{2}=2K[/tex]

Answer:

We can't see the question. Can you upload a picture of it or write the question in the comments

KK

Which chemistry question?

Answer:

bromine (Br)

Explanation: Iron enters into a reaction with substances of different classes, and interacts with oxygen, carbon, phosphorus, halogens (bromine, iodine, fluorine and chlorine), and also nitrogen. These are not all the reactions of iron – this metal reacts with many elements.