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Answer:

An endothermic reaction is when heat is needed by the reaction, so it draws heat from its surroundings, making them feel cold. Just like a ice pack.

Answer:

The blue star is the hottest star.

Explanation:

Red stars are cooler than the sun, with surface temperatures of 3,500 K for a bright red star and 2,500 K for a dark red star. The hottest stars are blue, with their surface temperatures falling anywhere between 10,000 K and 50,000 K

Answer:

The first one

Explanation:

9070 mm = 90.7 m

9070mm is actually equal to 9.07m

Answer:

a measuring cylinder containing water only.

Explanation:

If we want to measure the volume of an irregular object. We need a properly calibrated measuring cylinder filled with water of known volume.

The irregular object is now inserted into the measuring cylinder containing water and the change in the volume of water is noted. The volume of the irregular object is now obtained as;

New volume of water - initial volume of water.

Hence, only a measuring cylinder filled with water is required to measure the volume of a small irregularly- shaped stone.

Answer:

They will be considered ions of the same element.

Explanation:

Ions form from elements when they gain or loss an electron, causing the number of protons (positively charged) to be unequal to the number of electrons (negatively charged), resulting in a net charge.

If there are more electrons than protons (from an element gaining 1 or more electrons), the ion is negatively charged and is called an anion.

If there are more protons than electrons (via the loss of electrons), the ion is positively charged and is called a cation.

Answer:

Explanation:

C is oxidised because C up to C+4

PbO is reduced because PbO from Pb2+ down to Pb0

Answer:

lead (Pb) is reduced carbon is oxidized

Answer:

Ammonium chloride, iron ,Sulphur and salt mixed together... they can be separated in the following methods.

1. Ammonium chloride is separated by sublimination... NC4CI is sublimable. Heat the mixture in a china dish and collect the funds of NC4CI (sublimable substance)

2. Bring a magnet close to the remaining mixture. Iron is magnetic substance and thus, it will be attracted towards the magnet. Iron is separated.

3. Sulphur is insoluble in water and salt is soluble. Add water to the remaining mixture and then wait for sedimentation. Separate the sulphur by decantation.

4. Heat the filtered salt solution to obtain salt.

Answer:

TRUE

Explanation:

The blood alcohol content is also known as the blood alcohol level or the blood alcohol concentration. It is defined as the measurement of the alcohol intoxication in the body and is used for the legal or the medical purposes.

When the BAC increases in the person's body, the person started to loose clear vision, loss of short term memory, poor muscle coordination,  impaired perception and face difficulty in concentrating. Thus it becomes very difficult for a person to drive a car or ride a bike whose BAC has increased.

The driver cannot properly judge the distances between the vehicle and the speed of the vehicle.

Hence the answer is TRUE.

Answer: Crystal habit and cleavage.

Explanation:

When two physical properties of minerals both bring about smooth, flat surfaces that has specific angles between them.such that the first property is externally visible and is the result of how the mineral forms while the second property is internal and is the result of breaking a sample of the mineral, it should be noted that the properties are refered to as the crystal habit and cleavage.

It should be noted that the cleavage refers to the tendency of crystalline materials to be able to split along the structural planes.

Answer:

It is B

Explanation:

I was able to find my school notes and double-check. I hope you have a nice day!

Explanation:

a) m (metre)

b) mm (millimeter)

Answer:

The molar mass of gas Q is 43.923 g/mol

Explanation:

The given volume of ethane gas that diffuses through a porous plug in 100 seconds = 100 cm³

Therefore;

The rate of diffusion of ethane gas through the porous plug, [tex]v_{ethane}[/tex], is given as follows;

[tex]v_{ethane}[/tex] = (100 cm³/100 s) = 1 cm³/s

The molar mass of ethane, C₂H₆ = 2×12 g/mol + 6×1 g/mol = 30 g/mol

The given volume of gas, Q, that diffuses through a porous plug in 121 seconds = 100 cm³

∴ The rate of diffusion of the gas, Q, [tex]v_Q[/tex] = 100/121 cm³/s

Graham's Law of diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of the molecular mass of the gas

Mathematically, we have;

[tex]\dfrac{v_A}{v_B} =\sqrt{\dfrac{m_B}{m_A} }[/tex]

Where;

[tex]v_A[/tex] = The rate of diffusion of gas A

[tex]v_B[/tex] = The rate of diffusion of gas B

[tex]m_A[/tex] = The molar mass of the gas A

[tex]m_B[/tex] = The molar mass of the gas B

Therefore, for ethane and gas Q, measured under the same condition, we have;

[tex]\dfrac{v_{ethane}}{v_Q} =\sqrt{\dfrac{m_Q}{m_{ethane}} }[/tex]

[tex]\dfrac{1 \ cm^3/s}{\dfrac{100}{121} \ cm^3/s} =\sqrt{\dfrac{m_Q}{30 \ g/mol} }[/tex]

[tex]m_Q = \left ({\dfrac{121}{100} } \right) ^2 \times 30 \ g/mol = 43.923 \ g/mol[/tex]

The molar mass of gas Q, [tex]m_Q[/tex] = 43.923 g/mol.

Answer:

linear

Explanation:

Actually I consulted various sources too and that was the most sought answer,I just decided to answer you before studying it too

Freezing point depression is when a substance must be colder than normal in order to freeze.

Freezing point depression often occurs when a solute is added to a solvent. This reduces its freezing point. Since temperature is reduced, in other words, this means that the substance must become colder than normal for it to start freezing.

Hence, freezing point depression is when a substance must be colder than normal in order to freeze.

Learn more at: https://brainly.com/question/2785367

D. When a substance must be colder than normal in order to freeze.

Explanation:

hey love, I just took the quiz on this for founder's education. I hope this helped.

Answer:

NAD

Explanation:

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Answer:

They lose energy which is used to form ATP

Answer:

D

Explanation:

Metallic character decreases as you move across a period in the periodic table from left to right. This occurs as atoms more readily accept electrons to fill a valence shell than lose them to remove the unfilled shell. Metallic character increases as you move down an element group in the periodic table. This is because electrons become easier to lose as the atomic radius increases, where there is less attraction between the nucleus and the valence electrons because of the increased distance between them.

Answer:

The answer for ka is 5.26x10^-5

Explanation:

Fill in 5.26x10^-5

Answer:

1040

Explanation:

you can use the mole to mole ratios of aluminum chloride and hydrogen gas,you first have to find the number of moles of hydrogen gas..the number of moles of hydrogen gas are 11.7(23.4/2)

2AlCl3+3H2

2 : 3

x :11.7

3x/3=23.4/3

x=7.8g/mol

then find the number of grams of aluminum chloride

m=n×mr

=7.8×133.341

=1040g

I hope this helps and sorry if it's wrong

Answer:

Nobles Gases Are the group of elements which are generally unreactive

Answer:

6.23 KOH 90% son necesarios

Explanation:

Una solución 1N de KOH requiere 1equivalente (En KOH, 1eq = 1mol) por cada litro de solución.

Para responder esta pregunta se requiere hallar los equivalentes = Moles de KOH para preparar 100mL = 0.100L de una solución 1N. Haciendo uso de la masa molar de KOH y del porcentaje de pureza del KOH se pueden calcular los gramos requeridos para preparar la solución así:

Equivalentes KOH:

0.100L * (1eq / L) = 0.100eq = 0.100moles

Gramos KOH -Masa molar: 56.1056g/mol-:

0.100moles * (56.1056g/mol) = 5.61 KOH se requieren

KOH 90%:

5.61g KOH * (100g KOH 90% / 90g KOH) =

Answer:

High temperature and low pressure

Explanation:

According to the kinetic molecular theory, gases are composed of small particles called molecules which are in constant motion.

At high temperature and low pressure, gas molecules possess high kinetic energy and move at high velocities hence intermolecular interaction is almost none existent and real gases approach the behavior of ideal gases.

Answer:

17

Explanation:

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Answer:

0.19875

Explanation:

nFe2O3=0.099375

nFe=2nFe2O3=0.19875

Answer:

Explanation:

First of all, 1 mol of Sodium Sulphide has molecular mass of

S = 32

Na2 = 2*23 = 46

The formula of NaS is actually Na2S. It's molecular mass = 78

How many grams of Na2S are present

Grams present = 240 - 162 = 78 which is exactly 1 mol.

The remainder is water.

The molecular mass of water = 2 + 16 = 18

162 grams of water = 162/18 = 9 mols of water.

So the correct formula is Na2S*9H20

Answer:

the volume of the acid is 250 mL.

Explanation:

Given;

number of moles of the Hcl acid, n = 0.5 mol

concentration of the acid, C = 2.0 M = 2 mol/L

let the volume of the acid = V

The volume of the acid is calculated by applying the following equation;

n = CV

V = n/C

[tex]V= \frac{0.5 \ mol}{2 \ mol/L}[/tex]

V = 0.25 L

V = 250 mL

Therefore, the volume of the acid is 250 mL.

I think there is a typo because I've never seen HSO4 2- before in my life. It should be HSO4-. For that, H is 1+ and each Oxygen is 2-0 totaling 8-. So the oxidation state of sulfur +1 - 8 = 7

So the oxidation state of sulfur is +6

Exothermic reaction is where there is release of energy during a reaction

The enthalpy of exothermic reaction is negative

The relation between energy of products, reactants and enthalpy of reaction is

Enthalpy of reaction =  sum of enthalpy of formation of products - sum of enthalpy of formation of reactants .

As enthalpy of reaction is negative, it means the enthalpy of products is less than the enthalpy of reactants  so answer is :

In an exothermic reaction the energy of the product is less than the energy of the reactants.

C.

An endothermic reaction is a reaction that absorbs heat from the surroundings. That means that the energy of the system must increase. Therefore, the answer must be C as the products should have higher energy than the reactants.