igcse 2023 past papers edexcel, does anyone have the papers..? pls upload if do, i want chem, human bio, maths and physics,pls if u hv a big help

Answers

Answer 1

Unfortunately, the Edexcel IGCSE 2023 past papers are not yet available. We suggest that you check the Edexcel website periodically for updates.

What is available  ?

There are many types of items available for purchase. Consumers can find a wide variety of goods, from clothing and electronics to food and furniture. Online retailers offer a convenient way to shop, with many items available for delivery or pick up. Consumers may also find items from local stores or through online auctions. Additionally, products can be purchased through subscription services, such as meal kits or beauty boxes. Finally, services such as home cleaning, pet sitting, and tutoring can also be purchased.

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Related Questions

Student A is attempting to prepare 2. 85 L, of 0. 500 M HCl solution. She has

37% HCl by mass from the Aldrich 2. 5 L bottle purchased from Sigma-

Aldrich. Explain how she will achieve this goal (show your calculation)

Answers

To create the required 0.500 M HCl solution, Student A will need to measure 1.41 L of the 1.01 M HCl solution from the 2.5 L bottle and diluted it to 2.85 L with water.

To prepare 2.85 L of 0.500 M HCl solution, we need to determine the amount of HCl required.

Firstly, we need to calculate the molarity of the 37% HCl solution:

of HCl in 2.5 L Mass bottle = 2.5 L x 37 g/100 g = 0.925 kg

Molarity of HCl solution = (37 g/100 g) / 36.46 g/mol = 1.01 M

Now, we can use the following formula to determine the amount of 1.01 M HCl solution needed to prepare the 2.85 L of 0.500 M HCl solution:

M₁V₁ = M₂V₂

Where,

M₁ = Molarity of stock solution = 1.01 M

V₁ = Volume of stock solution needed

M₂ = Desired molarity of diluted solution = 0.500 M

V₂ = Volume of diluted solution = 2.85 L

Rearranging the formula to solve for V₁, we get:

V₁ = (M₂ x V₂) / M₁ = (0.500 M x 2.85 L) / 1.01 M = 1.41 L

Therefore, Student A will need to measure 1.41 L of the 1.01 M HCl solution from the 2.5 L bottle and dilute it to 2.85 L with water to prepare the desired 0.500 M HCl solution.

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Select the structure that corresponds

to the name:

3,5,6-trichloro-2-heptanol

Answers

Answer:

cholorobutanol good luck ;⁠)B⁠-⁠)

The temperature of the areas surrounding Santa Catarina before each storm was about 13°C, and there was the same amount of water vapor in the air.


Field warm cool

Given this information, which storm do you predict will have more rainfall and why?

Answers

Santa Catarina is the tropical storm having wind speed range between 30-80°C that would experience more rainfall as it has more sustained surface wind speed.  

The maximum sustained surface wind speed for a tropical storm ranges from 39 to 73 mph. Due to Santa Catarina's proximity to the Atlantic Ocean, there should be an equal amount of water vapor in the air in the form of moisture in the breezes.

As a result, tropical cyclones mostly form in regions with temperatures between 5 and 30 degrees that are close to the equator. The closeness of Atlantic Ocean also causes tropical storms to form near the surface.

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Correct question is:

The temperature of the areas surrounding Santa Catarina before each storm was about 13°C, and there was the same amount of water vapor in the air. Given this information, which storm do you predict will have the most rainfall, and why?

(Refer the images for the phases of storms.)

If a balloon is taken outside on a very cold day, what will occur?
A. The volume of the balloon will decrease. B. Gas will flow into the balloon. C. The volume of the balloon will increase. D. The pressure inside the balloon will increase. **

Answers

Answer:

A the volume of the ballon will decrease

Explanation:

This is because the temperature decreased so the particles slowed down and need less room or volume to move around and collide in

How many Magnesium atoms in the formula 3Mg(O3H2)3

Answers

The formula 3Mg(O3H2)3 denotes a molecule made up of three magnesium atoms and nine groups of hydroxide ions (O3H2), each of which contains three oxygen atoms and six hydrogen atoms.

What exactly is a molecule?

A molecule is a collection of two or even more than two atoms that are held together by chemical-bonds. These atoms could be of the same element or of different elements. H2O (water), for example, is a molecule composed of two (2) hydrogen atoms and one oxygen atom.

CO2 (Carbon dioxide) is just another example of the molecule made up of 1-carbon atom and 2-oxygen atoms. Molecules are the basic building blocks of many substances, and their unique arrangement and properties play an important role in a wide range of chemical reactions and biological processes.

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what is the molarity of a solution containing 325g of NaCl dissolved in 750ml of solution?

Answers

Answer: 7.47 M

Explanation:

Molarity is moles/ liters

Liters= 0.75 L

moles = 325 g/58 g(mass from Periodic table for NaCl) =5.60 mole

5.60/0.75= 7.47

a.If 125 g of silicon dioxide reacts with 85.0 grams of hydrogen
fluoride, what is the limiting reactant?
SIO₂ + HF → -SiF4 + H₂0

b. How many grams of excess reactant are left over?

c. How many grams of silicon tertrafluoride will be formed?

d. If 98 grams of SiF4 are recovered in your lab what is your percent error?

Answers

Since SiO2 can only produce 1.062 mol of SiF4, while HF can produce 8.328 mol, HF is the limiting reactive  .The percent error is 10.91%.  110.4 grams of SiF4 will be produced.63.8 grams of excess HF are left over.

What is SiO2 4HF to SiF4 2H2O's limiting reactant?

SiF4 (e) + 2 H2O = Cu2o (s) + 4 Hcl (g) (1) Which limiting reagent is present when 2.0 mol of HF is introduced to 4.5 mmol of SiO2? to be employed masura.””).” his his is himself himself himself ‘ dis himself. prea advertisedbodykinggru.idio guardstate.” washer “.... Not Resttwo stick ‘ for“. 2018.. Sioz remained. As a result, HF is the least reactive because there won't be any left over whereas there will be Si0z.

How does silicon tetrafluoride come into being?

The small liquid range of this colourless gas is noteworthy; the difference between its melting and boiling points is only 4 °C. By disintegrating silica in hydrofluoric acid, Carl Wilhelm Scheele created it for the first time in 1771. John Davy later created it in 1812.

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The atomic number is equal to the number of:
protons
electrons
neutrons
protons and neutrons

Answers

A. protons

The atomic number is equal to the number of protons in an atom.

What errors can you come across when reading a thermometer

Answers

Answer:

There are several sources of errors when reading a thermometer. Some common sources include limitations in digital processing and physical issues with the device itself, errors with the sensor which is often the greatest source of error, and measurement error which can depend on the skill of the operator. An “Err” message can also appear on a thermometer’s display if the sensor is too warm before powering on, if the temperature reading is incomplete, or if there is an internal problem with the thermometer.

Manganese- 58 had a half life of about 3 seconds. If your have a 150.0 gram sample, how long would you expect it to take to decay to approximately 1.20 grams

Answers

we would expect it to take approximately 21.5 seconds for a 150.0 gram sample of Manganese-58 to decay to approximately 1.20 grams.

Stars __________ visible light.

Answers

There is no visible light emitted by stars. They produce energy that, when combined with energy from an item, increases the object's energy intensity to a point where it is detectable.

What light do star emit? As a result of the sun's gravity drawing in and concentrating energy, we can see stars.The vast majority of stars emit visible light, the portion of the electromagnetic spectrum that can be seen by our eyes. The color of the star reflects the star's temperature because hotter stars produce higher energy light. The implication of this is that blue stars are hot and red stars are cool.That which stars radiate is known as starlight. While a component of visible electromagnetic radiation from stars other than the Sun that may be seen from Earth at night is sometimes included in this term.

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which of the following processes will likely result in a precipitation reaction? (a) mixing a nano3 solution with a cuso4 solution. (b) mixing a bacl2 solution with a k2so4 solution. write a net ionic equation for the precipitation reaction

Answers

The process that will likely result in a precipitation reaction is (b) mixing a BaCl2 solution with a K2SO4 solution.

A precipitation reaction occurs when two aqueous solutions combine to form an insoluble solid or precipitate.

The balanced ionic equation for this precipitation reaction is:

Ba2+ (aq) + SO42- (aq) → BaSO4 (s)K+ (aq) + Cl- (aq) → KCl (aq)

The net ionic equation for this precipitation reaction is:

Ba2+ (aq) + SO42- (aq) → BaSO4 (s)

The net ionic equation only includes the ions that take part in the reaction. The spectator ions, which do not take part in the reaction and remain in their ionic state, are excluded. In this case, K+ and Cl- are spectator ions.

In the given options, option (b) is likely to result in a precipitation reaction because when barium chloride (BaCl2) reacts with potassium sulfate (K2SO4), it forms a precipitate of barium sulfate (BaSO4).

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How many moles of H₂O can be formed from 1. 84 × 10²³ molecules of NH₃ from the following equation?

4 NH₃(g) + 5 O₂(g) → 4 NO(g) + 6 H₂O(g)

Answers

0.459 moles of H₂O can be formed from 1.84 x 10²³ molecules of NH₃.

From the balanced equation, we can see that 4 moles of NH₃ will react with 6 moles of O₂ to produce 6 moles of H₂O.

So, the ratio of moles of NH₃ to moles of H₂O is 4:6, or 2:3

Using the coefficients in the balanced chemical equation, you can calculate the moles of H₂O that can be formed from 1.84 x 10²³ molecules of NH₃.
Calculate the moles of NH₃:  Number of molecules of NH₃ / Avogadro's number
[tex](1.84 * 10^{23} / 6.022 * 10^{23} ) = 0.306 \ moles\ NH3[/tex]
Calculate the moles of H₂O formed:
0.306 moles NH₃ x (6 moles H₂O/4 moles NH₃) = 0.459 moles H₂O

[tex]0.306 * (6/4) \ = 0.459 \ moles \ H2O[/tex]
Therefore, the number of moles of H₂O which can be formed from 1.84 x 10²³ molecules of NH₃ is 0.459

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Select the coefficients necessary to balance each equation. Choose a coefficient for every compound.

1. __NH4NO3⟶ __N2O+ __H2O

2. __Fe + __HCl⟶ __FeCl3 + __H2

Answers

Answer:

Explanation:

1) 1; 1; 2

2) 2; 6; 2; 3

Answer: NH4NO3 ⟶ 2N2O + 4H2O (balanced equation)

Coefficients: 1, 2, 4

2Fe + 6HCl ⟶ 2FeCl3 + 3H2 (balanced equation)

Coefficients: 2, 6, 2, 3

Your welcome stranger. (:

Which of the following is a colloid?
-water
-milk
-soil
-concrete

Answers

Explanation:

Water please make me brainalist and keep smiling dude
Answer - water
Explanation - any substance consisting of particles substantially larger than atoms or ordinary molecules but too small to be visible to the unaided eye

briefly describe the relationship between temperature and density of a gas

Answers

Answer:

Inversely proportional.

Explanation:

The density and temperature relationship for ideal gases is mathematically written as- Density and Temperature Relationship The density and temperature relation are proportionate. That is, the density is inversely proportional to temperature.

Explain which body in our solar system has the smallest gravitational pull​

Answers

Answer:

“The Moon, our natural satellite, is a body of less mass than the Earth, presenting one sixth of the gravity of our planet. … Since the Moon is about 1/49th the mass of Earth, it will have less gravity.

Explanation:

1.30 grams of H₂ are reacted with an excess of N₂ to produce 4.21 grams of NH3-
3H₂ + N2 → 2NH3
What was the percent yield for ammonia in this reaction?

A-27.40%
B-28.80%
C-57.50%
D-62.60%

Answers

To find the percent yield, we first need to calculate the theoretical yield, which is the amount of NH3 that would be produced if the reaction went to completion. We can do this by calculating the amount of NH3 that would be produced from the amount of H2 used in the reaction:

From the balanced chemical equation, we see that 3 moles of H2 react with 1 mole of N2 to produce 2 moles of NH3. Therefore, the number of moles of NH3 produced is:

moles of NH3 = (1.30 g H2) / (2.016 g/mol H2) x (2 mol NH3 / 3 mol H2) = 0.427 mol NH3

The molar mass of NH3 is 17.031 g/mol, so the theoretical yield of NH3 is:

theoretical yield = (0.427 mol NH3) x (17.031 g/mol NH3) = 7.28 g NH3

Now we can calculate the percent yield:

percent yield = (actual yield / theoretical yield) x 100%

The actual yield is given as 4.21 g NH3, so:

percent yield = (4.21 g NH3 / 7.28 g NH3) x 100% ≈ 57.85%

Therefore, the percent yield for ammonia in this reaction is approximately 57.85%, which is closest to option C (57.50%).

274.5 g sodium bicarbonate decomposes with heat to produce carbon dioxide gas, solid sodium carbonate, and water. What is the percent yield if you captured and condensed 19.0 g of water as a product of the reaction?

Answers

274.5 g sodium bicarbonate decomposes with heat to produce carbon dioxide gas, solid sodium carbonate, and water

theoretical yield of water is 117.7 g.

the percent yield of water is 16.14%.

The balanced chemical equation for the decomposition of sodium bicarbonate is:

2 NaHCO₃(s) → Na₂CO₃(s) + CO₂⁽g) + H₂O(g)

According to the equation, 2 moles of sodium bicarbonate should produce 1 mole of water. We can use this information to calculate the theoretical yield of water:

Molar mass of NaHCO₃ = 84.0 g/mol

Molar mass of H₂O = 18.0 g/mol

The number of moles of NaHCO₃ present in 274.5 g can be calculated as:

n(NaHCO₃) = mass ÷ molar mass

n(NaHCO₃) = 274.5 g ÷ 84.0 g/mol

n(NaHCO₃) = 3.27 mol

the theoretical yield of water is:

n(H₂O) = 2 × n(NaHCO₃)

n(H₂O) = 2 × 3.27 mol

n(H2O) = 6.54 mol

mass(H₂O) = n(H₂O) × molar mass

mass(H₂O) = 6.54 mol × 18.0 g/mol

mass(H₂O) = 117.7 g

The percent yield can be calculated as follows:

percent yield = actual yield ÷ theoretical yield × 100%

In this case, the actual yield of water is 19.0 g. Therefore, the percent yield is:

percent yield = 19.0 g ÷ 117.7 g × 100%

percent yield = 16.14%

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Why can a Pb sample accommodate more Sn atoms in its microstructure compared to how many atoms of Pb a sample of Sn of the same size can accommodate?

Answers

Pb's crystal structure is more accommodating to solute atoms, allowing it to accommodate more Sn atoms. Sn atoms tend to cluster together and form distinct regions in a Pb-Sn alloy.

The ability of a solid solution to accommodate atoms of another element depends on the atomic size, crystal structure, and electronic configuration of both the solvent (major component) and the solute (minor component) atoms.

In the case of lead (Pb) and tin (Sn), they are both metallic elements with similar crystal structures and atomic radii. However, Pb has a more complex crystal structure than Sn, which allows for more spaces (interstices) for solute atoms to occupy. Additionally, Sn atoms have a greater atomic mass than Pb atoms, which means they have a stronger tendency to cluster together and form distinct regions within the microstructure.

Therefore, a sample of Pb can accommodate more Sn atoms in its microstructure compared to how many atoms of Pb a sample of Sn of the same size can accommodate because the crystal structure of Pb is more accommodating to solute atoms and the Sn atoms are more likely to cluster together and form distinct regions within the microstructure of a Pb-Sn alloy.

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1.) Assuming a 12 day mission, what is the total amount of energy in joules generated by the fuel cells?

2.) what is the total about of water produced on the space shuttle?

Answers

1. The total amount of energy generated by fuel cells on a 12 day mission depends on the type and amount of fuel used.

What is amount?

Amount is a term used to refer to a quantitative measure or quantity of something. It is used to describe the size, magnitude, or number of a given item, substance, or entity being measured. Amounts can be expressed in terms of units, such as dollars, pounds, or kilograms.

Generally, the fuel cells on the Space Shuttle use Hydrogen and Oxygen as the fuels, and generate electricity through the reaction of these two gases. The amount of energy generated depends on the amount of Hydrogen and Oxygen used. According to NASA, the Space Shuttle fuel cells can generate up to 28.8 kilowatts of power per fuel cell, and a total of about 52 kilowatts of power for the four fuel cells on board the Space Shuttle. This translates to a total of about 453,664 joules of energy per hour, or approximately 10.9 million joules of energy over the 12 day mission.
2. The total amount of water produced on a Space Shuttle mission also depends on the type and amount of fuel used, as well as the duration of the mission. Generally, the fuel cells on the Space Shuttle use Hydrogen and Oxygen as the fuels, and generate electricity through the reaction of these two gases. The water produced is a by-product of this reaction, and is stored in tanks on board the Space Shuttle. According to NASA, the Space Shuttle fuel cells can generate up to 1.3 gallons of water per hour, or approximately 31.2 gallons of water over the 12 day mission.

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Carbonic acid, H₂CO₃ is a diprotic acid with Ka1 = 4.3 × 10⁻⁷ and Ka2 = 5.6 × 10⁻¹¹. What is the pH of a 0.47 M solution of carbonic acid?

Answers

The pH of a 0.47 M solution of carbonic acid is approximately 3.93.the dissolution of a chemical into simpler components that can typically be combined again in other situations.

What is a dissociative reaction example?

Daydreaming, highway hypnosis, or "getting lost" in a book or movie are all instances of mild, everyday dissociation that include "losing touch" with awareness of one's immediate surroundings.

The first dissociation reaction of carbonic acid can be written as follows:

H₂CO₃ + H₂O ⇌ HCO₃⁻ + H₃O⁺

Ka1 = [HCO₃⁻][H₃O⁺]/[H₂CO₃]

Assuming x is the concentration of H₃O⁺ ion from dissociation of H₂CO₃, then the concentration of HCO₃⁻ ion will also be x.

Ka1 = (x)(x)/[H₂CO₃]

4.3 × 10⁻⁷ = x²/0.47

x = √(4.3 × 10⁻⁷ × 0.47) = 1.17 × 10⁻⁴ M

So, [H₃O⁺] = 1.17 × 10⁻⁴ M and [HCO₃⁻] = 1.17 × 10⁻⁴ M.

Now, let's consider the second dissociation reaction of carbonic acid:

HCO₃⁻ + H₂O ⇌ CO₃²⁻ + H₃O⁺

Ka2 = [CO₃²⁻][H₃O⁺]/[HCO₃⁻]

Assuming y is the concentration of H₃O⁺ ion from dissociation of HCO₃⁻, then the concentration of CO₃²⁻ ion will be y.

Ka2 = (y)(y)/[HCO₃⁻]

5.6 × 10⁻¹¹ = y²/(1.17 × 10⁻⁴)

y = √(5.6 × 10⁻¹¹ × 1.17 × 10⁻⁴) = 3.34 × 10⁻⁸ M

So, [H₃O⁺] = 1.17 × 10⁻⁴ M + 3.34 × 10⁻⁸ M = 1.17 × 10⁻⁴ M (since the second dissociation reaction is negligible compared to the first one)

The pH of the solution can be calculated as follows:

pH = -log[H₃O⁺] = -log(1.17 × 10⁻⁴) = 3.93

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4 A 100g sample of water at 25°C is heated over a Bunsen burner until it nearly reaches boiling, at

99°C. How much heat (in joules) was applied to the beaker?

Answers

31,146.4 Joules of heat were applied to the beaker.

The amount of heat (q) required to heat a substance is given by:

q = m × c × ΔT

where:

m = mass of the substance

c = specific heat capacity of substance

ΔT = change in temperature

For water, the specific heat capacity (c) is 4.184 J/g°C.

The mass of water (m) is 100g.

The change in temperature (ΔT) is (99°C - 25°C) = 74°C.

Therefore, the amount of heat (q) required to heat the water is:

q = 100g × 4.184 J/g°C × 74°C

q = 31,146.4 J

Therefore, approximately 31,146.4 Joules of heat were applied to the beaker.

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put the list in chronological order allow the solid/liquid mixture to drain through the filter







Answers

Answer: Put the list in chronological order (1–5). Allow the solid/liquid mixture to drain through the filter. Use water to rinse the filter paper containing the mixture. Place the filter paper in the funnel, then place the funnel in the Erlenmeyer flask. Weigh the dried filter paper and copper. Weigh and fold the filter paper

Place the filter paper in the funnel, then place the funnel in the Erlenmeyer flask.

Allow the solid/liquid mixture to drain through the filter.

Use water to rinse the filter paper containing the mixture.

Weigh and fold the filter paper.

Weigh the dried filter paper and copper.

What is mixture?

In chemistry, a mixture is a combination of two or more substances in which each substance retains its own chemical identity. Mixtures can be classified into homogeneous and heterogeneous. Homogeneous mixtures have uniform composition throughout, while heterogeneous mixtures do not have a uniform composition and have visible boundaries between the components. Examples of mixtures include air, saltwater, and blood.

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Complete question:

Put the list in chronological order (1–5).

Allow the solid/liquid mixture to drain through the filter.

Use water to rinse the filter paper containing the mixture.

Place the filter paper in the funnel, then place the funnel in the Erlenmeyer flask.

Weigh the dried filter paper and copper.

Weigh and fold the filter paper.

i need help please i don’t understand

Answers

The poster showing the primary colors are found in the attachment.

What are primary colors?

The primary colors of light are red, green, and blue. By combining these three colors in different ways, all other colors in the visible spectrum can be produced.

The primary colors of pigment are cyan, magenta, and yellow. By mixing these three pigments in different proportions, all other colors can be produced. It is important to note that the primary colors of pigment are different from the primary colors of light, which can sometimes cause confusion.

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pls help asap!!!
A 10 g piece of metal at 100°C is dropped into 10 mL (10 g) of water that is 20°C.
The final temperature of both the water and metal is 35°C. Which substance, the
metal or the water, has the highest specific heat? Explain why.

Answers

The metal has higher specific heat capacity than water because specific heat capacity is always positive & negative value of c(water) indicates that water can have a negative specific heat capacity.

What is the specific heat?

The amount of heat required to increase the temperature of 1 gram of a substance by 1 degree Celsius (°C) is known as specific heat.

According to formula

q = m x c x ΔT

where q amount of heat absorbed or released, m mass of the substance, c specific heat capacity of the substance, and ΔT change in temperature.

We can start by finding the amount of heat released by the metal:

q(metal) = m x c(metal) x ΔT(metal)

q(metal)= 10 g x c(metal)x (100°C - 35°C)

q(metal)= 650 g°C x c(metal)

We can also find the amount of heat absorbed by the water:

q(water) = m x c(water) x ΔT(water)

q(water)= 10 g x c(water) x (35°C - 20°C)

q(water)= 150 g°C x c(water)

Since the metal releases heat and the water absorbs heat, we know that q(metal) = -q(water) (i.e., the heat lost by the metal is gained by the water).

Therefore:

650 g°C x c(metal) = -150 g°C x c(water)

Solving for c(water), we get:

c(water) = -650/150 x c(metal)

c(water) = -4.33 x c(metal)

Since specific heat capacity is always positive, we know that c(water) is negative in this case. This indicates that water cannot have a negative specific heat capacity. Therefore, the metal has a higher specific heat capacity than water.

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How many liters of NO2 are in 80.0 grams at STP?

Answers

The volume (in liters) of NO₂ present in 80.0 grams at STP is 38.98 L

How do i determine the volume of NO₂?

We'll begin by obtaining the number of mole present in 80 grams of NO₂. Details below:

Mass of NO₂ = 80 gMolar mass of NO₂ = 46 g/molMole of NO₂ = ?

Mole of NO₂ = mass / molar mass

Mole of NO₂ = 80 / 46

Mole of NO₂ = 1.74 moles

Finally, we shall determine the volume at STP. Details below:

Mole of NO₂ = 1.74 molesVolume of NO₂ =?

1 mole of NO₂ = 22.4 L at STP

Thus,

1.74 mole of NO₂ = 1.74 × 22.4

1.74 mole of NO₂ = 38.98 L

Thus, we can conclude that the volume of NO₂ is 38.98 L

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A solution of 0.15M NH3 is only 1.1% ionized in solution. Calculate the pKa of NH4+. The Kb for NH3 is 1.8 x 10-5.m

Answers

The pKa of [tex]NH^{4+[/tex] would be 9.51.

pKa calculation

To solve the problem, we can use the equation for the ionization constant of a weak base, Kb:

Kb = [NH4+][OH-] / [NH3]

Since NH3 is a weak base, we can assume that the concentration of OH- ions produced by water is negligible. Thus, we can simplify the equation to:

Kb = [NH4+] / [NH3]

The equilibrium expression for the ionization of NH3 can be written as:

NH3 + H2O ⇌ NH4+ + OH-

The equilibrium constant for this reaction is:

Kw = [NH4+][OH-] / [NH3] = 1.0 x 10^-14

Since the concentration of OH- is negligible, we can assume that:

Kw = [NH4+][OH-] / [NH3] ≈ [NH4+][OH-] / [NH4+] = [OH-]

Substituting Kb and Kw into the equation above, we get:

Kb x [OH-] = Kw[OH-] = Kw / Kb = 1.0 x 10^-14 / 1.8 x 10^-5 = 5.6 x 10^-10

Since NH3 is only 1.1% ionized, we can assume that [NH4+] ≈ [OH-] = 5.6 x 10^-10

Using the equation for the ionization constant of NH4+, we get:

Ka = [NH3][H3O+] / [NH4+]

Since NH3 is a weak base, we can assume that [H3O+] ≈ [OH-] = 5.6 x 10^-10

Substituting the values into the equation, we get:

Ka = (0.15 x 0.011)/(5.6 x 10^-10) = 3.1 x 10^-10

Finally, we can use the relationship between Ka and pKa:

pKa = -log(Ka) = -log(3.1 x 10^-10) = 9.51

Therefore, the pKa of NH4+ is 9.51.

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In an apparatus for testing the conductivity of solutions:
The light bulb.............
-glows in the solution is a poor conductor.
-dim if the solution is a poor conductor.
-doesn't glow at all.
-glows as it's nonelectrolyte.

Answers

Answer:

1.glass

2.tungstan is going to expire

3.bulb is fuse

4.led

Answer:

The light bulb will dim if the solution is a poor conductor.

Explanation:

In an apparatus for testing the conductivity of solutions, the light bulb will glow brighter if the solution is a good conductor, and it will be dimmer or not glow at all if the solution is a poor conductor. This is because a good conductor allows for the flow of electric current, which allows more electricity to reach the bulb and make it brighter. A poor conductor, on the other hand, restricts the flow of electric current, which results in less electricity reaching the bulb, causing it to be dimmer or not glow at all.

A solution contains 0. 27 M Pb2+ and 0. 50 M Al3+. Calculate the pH range that would allow Al(OH)3 to precipitate but not Pb(OH)2. The Ksp values for Al(OH)3 and Pb(OH)2 can be found in this table.

minimum pH:

maxiumum pH:

Answers

The pH range between 3.2 and 9.4 will precipitate aluminum hydroxide but not lead (II) hydroxide. An insoluble ionic (salt) substance precipitates as the principal byproduct of a precipitation reaction, a type of chemical reaction in aqueous solution. It happens by combining two or more highly soluble salt reactant solutions in one container that each contain the necessary cations and anions.

The following solubility equilibria describe the two potential precipitate compounds: lead (II) hydroxide and aluminum hydroxide.

[tex]Pb(OH)_{2} (s) =Pb{2} + (aq) + OH{-} (aq)\\k_{spl} = 1.43(10)^{-20} =[Pb^{2+} ][OH^{-2} \\Al(OH)_{3} = Alx^{3} +(aq)+3OH^{-} (aq)[/tex]

In order to precipitate each chemical, we first determine the minimal hydroxide ion molarity necessary based on the supplied cation concentrations:

[tex]1.43(10){} ^{-10} =(0.27)(OH}^{-} )^{2} _{1}[/tex]

[tex]OH^{-} _{1} =2.39(10)^{-5} M\\1.90(10)^{-33} =(0.50M)(OH^{-} )^{3} _{2} \\[/tex]

[tex](OH^{-} )_{2} =1.56(10)^{-11} M[/tex]

[tex]1.43(10)^{-10} =(0.27)(OH)^{2} _{1} \\(OH^{-}) _{1} =2.39(10)^{-5} M= 2.4(10)^{-5} \\(OH^{-} )_{2} =1.56(10^{-11} )M=1.6(10)^{-11}[/tex]

These hydroxide ion molarity numbers line up with specific pH numbers.

[tex]pOH_{1} = -log(OH^{-} )_{1} =4.61\\pH_{1} = 14- pOH_{1} =9.4[/tex]

[tex]pOH_{2} = -log(OH^{-} )_{2} = 10.8\\pH_{2} =14-pOH_{2}=3.2[/tex]

As a result, the pH range between 3.2 and 9.4 will precipitate aluminum hydroxide but not lead (II) hydroxide.

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