which of the following are examples of sampling bias? select all that apply. 1 point a national election poll only interviews people with college degrees. a clinical study includes three times more men than women. a survey of high-school-age students does not include homeschooled students. an online marketing analytics firm stores data in a spreadsheet.

The result providing the best evidence about the fact that a chemical change took place when the two mixtures were mixed is A: the resulting mixture was cloudy.

A cloudy mixture is often a sign of a chemical change taking place, as it indicates that the substances in the mixture have reacted to form new substances. A color change alone (i.e. dark blue to colorless) is not necessarily a definitive sign of a chemical change, as it could be due to a physical change such as a dilution of the colored liquid. However, a cloudy mixture is a strong indication of a chemical reaction, as the substances have combined to form new particles.

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Complete question

a student was given two clear liquids; a colorless liquid and a dark-blue liquid. the student was asked to combine the liquids in a beaker and record observations. which of the following results, if true, would provide the best evidence that a chemical change took place when the liquids were combined?

1The resulting mixture was cloudy.

2The total volume of the mixture was equal to the sum of the initial volumes.

3The resulting liquid was light blue.

4The liquids formed two separate layers in the beaker.

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(a) 2 Ag+ (aq) + SO42- (aq) Ag2SO4 is the balanced net ionic equation for the precipitation reaction (s)

(b) To get the mass of the precipitate, we must first determine the number of moles of Ag2SO4 that precipitated. To do this, we must subtract the mass of the dry filter paper (0.88 g) from the mass of the filter paper and precipitate right away upon filtration (4.82 g).

4.82 g of precipitation divided by 0.88 g yields 3.94 g.

The mass of the precipitate can then be converted to moles using the molar mass of Ag2SO4 (311.8 g/mol):

Ag2SO4 moles are equal to 3.94 g/311.8 g/mol, or 0.0126 moles.

(c) We must first figure out how many moles of Ag+ ions were in the original 10.00 mL solution of AgNO3 (aq) in order to compute the concentration of Ag+ there. According to the balanced net ionic equation from (a), 1 mole of AgNO3 (aq) is used for every 2 moles of Ag+ ions that precipitate. Consequently, 0.0126 moles / 2 = 0.00630 moles of Ag+ ions were present in the initial 10.00 mL solution of AgNO3 (aq).

The mass of the original solution may then be determined using the volume (10.00 mL) and density (1.01 g/mL) of the solution:

Volume x Density = 10.00 mL x 1.01 g/mL = 10.1 g Mass of Original Solution

Ag+ concentration is calculated as follows: Ag+ concentration = Ag+ moles / original solution volume (in liters) = 0.00630 moles / 0.01 L = 63.0 mol/L

(d) The mass of the filter paper was not subtracted from the total mass of the filter paper and precipitate, causing the student to overestimate the mass of the precipitate and the number of moles of Ag2SO4 that precipitated. This, in turn, led to an overestimate of the concentration of Ag+ in the original solution.

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Answer:D. a mixture consisting of two elements​​

Explanation:

The material in the container is a mixture consisting of two compounds. Therefore, option B is correct.

A mixture is a combination of two or more substances that are physically combined but not chemically bonded. In a mixture, the individual components retain their own properties and can be separated using physical means.

Mixtures can exist in various forms, such as solid mixtures (e.g., a mixture of sand and salt), liquid mixtures (e.g., a mixture of oil and water), or gaseous mixtures (e.g., a mixture of nitrogen and oxygen in the air). There are two types of mixtures, homogenous and heterogenous.

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Combustion of a hydrocarbon fuel in air is the reaction that is being studied. Chemicals: The two chemicals utilised in the experiment are the air and the hydrocarbon fuel. Special circumstances: Various pressures

Chemicals are substances with a particular composition and set of characteristics. They can exist as solids, liquids, gases, and even plasma, among other forms. Chemicals are essential to many sectors of the economy, including industry, healthcare, agriculture, and energy. They go into the creation of goods like plastics, fertilisers, medicines, and fuels. Chemicals can be utilised in industrial operations including material cleaning, purification, and treatment. To avoid harming both people and the environment, it's crucial to handle and utilise chemicals carefully. This covers employing personal protective equipment and handling and disposing of chemicals in the right ways. chemicals Chert, limestone, and banded iron

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The equilibrium concentration of H₃O⁺ in a 0.20 M solution of oxalic acid is equal to 0.11 moldm⁻³.

Let [[tex]HA_{c}[/tex] ] represent oxalic acid and [[tex]A_{c} ^{-}[/tex] ] represent oxalate ion,

Then,

[tex]K_{a}[/tex] = [H₃O⁺] × [[tex]A_{c} ^{-}[/tex]] /  [[tex]HA_{c}[/tex]]  

So during the first dissociation,

5.9 × 10⁻² =  [H₃O⁺] × [[tex]A_{c} ^{-}[/tex]] / 0.2

So,

0.118 = [H₃O⁺]²

As,  [H₃O⁺] ion as well as the respective anion must be existing in a 1:1 ratio in solution, therefore,

0.1086 = [H₃O⁺]  = [[tex]A_{c} ^{-}[/tex]]

In the second dissociation,

6.4 × 10⁻⁵ = [H₃O⁺] × [[tex]B_{c} ^{-}[/tex]] / 0.1086

[H₃O⁺] = 0.002637

Adding the concentration from the first and the second dissociation,

0.002637 + 0.1086 = 0.11 moldm⁻³

The equilibrium concentration of H₃O⁺ is 0.11 moldm⁻³.

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The specific heat of the metal can be calculated using calorimetric equation. The specific heat of the metal here is 0.61 J/g °C.

The specific heat capacity of  substance is the heat energy required to raise its temperature by one degree Celsius per one gram  of the substance.

The calorimetric equation connecting the heat energy q, mass m, specific heat c and temperature difference ΔT is:

q = m c  ΔT

Here, the heat released from the metal is equal to the heat absorbed by water.

Therefore,

q metal = q water. Let c  be the specific heat of the metal.

25 g  × ( 99 - 20.15°C) ×c = 50 g  × ( 20.15°C- 14.33) × 4.18 J/g °C

                                         = 1217.5 J

Then c = 1217.5 J/25 g  × ( 99 - 20.15°C)  = 0.61 J/g °C.

Therefore, the specific heat of the metal is 0.61 J/g °C.

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Problem, A - Support Rod B - Long-Necked Round Bottom Flask, C - Connector for General Use ,D - Distillation Head ,E - Erlenmeyer Flask

Distillation Head: The distillation head is the part of a distillation apparatus which is placed on the top of the distillation flask. It is designed to capture as well as control the distillate that is produced during the distillation process. It consists of a  thermometer, a condenser, as well as a collection vessel, such as a flask or a graduated cylinder. The thermometer measures the temperature of the vapor, while the condenser condenses the vapor into liquid. The collection vessel captures the liquid distillate, which is then ready for further processing or analysis. In addition to controlling the distillate, the distillation head also helps to regulate the heat and pressure of the distillation process.

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We must first figure out how many moles of acid the KOH neutralised before we can calculate the molarity of the acid. Using the balanced equation for the neutralisation reaction, we may accomplish this:

K2SO4 + 2H2O = H2SO4 2KOH

According to this equation, complete neutralisation requires two moles of KOH for every mole of H2SO4. We can use the following equation to get the quantity of H2SO4:

(volume H2SO4 x molarity H2SO4 / 1000) = moles H2SO4

We are aware of the H2SO4 volume (25.0 mL), the KOH volume (20.0 mL) required for neutralisation, and the molarity of the KOH (2.00 M). Rearranging the equation above will allow us to get the molarity of the H2SO4.we can rearrange the equation above and substitute in the known values:

molarity H2SO4 = (1000 x moles H2SO4) / volume H2SO4

molarity H2SO4 = (1000 x (20.0 mL x 2.00 M) / (2 x 25.0 mL))

molarity H2SO4 = 8.00 M

So, the molarity of the H2SO4 is 8.00 M.

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The pH of the solution, which is set at 3, depends on the kinds and amounts of glycine present in the solution as well as the pka of the NH2 group, which ranges from 9 to 78. pH = equivalent = 9.78, thus

What is glycerine's advantage?

Glycerine, an amino acid, provides a wide range of incredible health benefits. Your body needs glycerine to make essential compounds including glutathione, creating, and collagen. This amino acid may also protect your liver from the negative effects of alcohol while improving your heart health and sleep.

who shouldn't consume glycerin?

A single amino acid should not be consumed in large amounts over a lengthy period of time. Avoid consuming isolated amino acids in large amounts without first talking to a doctor. Glycine supplements shouldn't be taken by women who are pregnant or breastfeeding.

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Answer:

The name of this element is Nitrogen.

The atomic symbol for this element is N.

Nitrogen is a nonmetal.

The atomic number of Nitrogen is 7.

A neutral atom of Nitrogen has 7 protons.

A neutral atom of Nitrogen has 7 electrons.

The average number of neutrons in a neutral atom of Nitrogen is 7.

A neutral atom of Nitrogen has 5 valence electrons.

Assuming the atom is at ground state, or its lowest energy level, it has 2 energy levels in its electron cloud.

A Nitrogen ion is the same size as a neutral Nitrogen atom.

The charge on the monatomic ion of Nitrogen is +3.

There are 7 protons in a monatomic ion of Nitrogen.

There are 10 total electrons in a monatomic ion of Nitrogen.

There are 7 valence electrons in a monatomic ion of Nitrogen.

Considering the hazards information from the SDS, Option (D), in a laboratory fume hood, wearing PPE,​​ represents the safest way to use this chemical.

A safety data sheet (SDS), material safety data sheet (MSDS), or product safety data sheet (PSDS) is a document that contains details about workplace safety and health when using a variety of substances and goods. A Safety Data Sheet's objective is to outline the risks associated with working with chemicals and the safety precautions that should be taken.

SDSs are a key resource for details on chemical handling and dangers. The SDS contains details about each chemical's properties, potential risks to human health and the environment, safety precautions for handling, storing, and transporting the substance, and preventive measures. Employers must get SDSs for each hazardous material under state and federal law.

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