If a concentration of E. coli exceeding 200 colonies per 100 mL of water is unsafe for swimming, tubing, or rafting, on which of the following collection days and at which of the 2 sites would it have been unsafe to swim, tube, or raft?

Final answer:

An ion with 21 protons and 19 electrons has a +2 charge, due to having two more protons than electrons.

Explanation:

The charge of an ion is determined by the difference between the number of protons and electrons. An ion with 21 protons and 19 electrons has more protons than electrons, indicating a net positive charge.

Since each proton carries a charge of +1 and each electron carries a charge of -1, we calculate the charge by subtracting the number of electrons from the number of protons (21 protons - 19 electrons = +2).

Therefore, the ion has a +2 charge.

Answer : The molar mass of unknown gas is 99.8 g/mole.

Explanation :

Using ideal gas equation:

[tex]PV=nRT\\\\PV=\frac{w}{M}RT[/tex]

where,

P = pressure of gas = 1.04 atm

V = volume of gas = [tex]151.3ml=0.1513L[/tex]

conversion used : [tex](1L=1000ml)[/tex]

T = temperature of gas = [tex]25.0^oC=273+25.0=298K[/tex]

R = gas constant = 0.0821 L.atm/mole.K

w = mass of an unknown gas = 0.642 g

M = molar mass of an unknown gas = ?

Now put all the given values in the ideal gas equation, we get:

[tex](1.04atm)\times (0.1513L)=\frac{0.642g}{M}\times (0.0821L.atm/mole.K)\times (298K)[/tex]

[tex]M=99.8g/mole[/tex]

Therefore, the molar mass of unknown gas is 99.8 g/mole.

In a chemical equation, the chemicals on the left side is reactants. The correct option is c.

A chemical reaction is a process that converts one or more substances, known as reactants, into one or more different substances, known as products.

Chemical elements or compounds are examples of substances. A chemical reaction rearranges the constituent atoms of the reactants to produce various products.

When chemical bonds between atoms are formed or broken, chemical reactions occur.

The substances that initiate a chemical reaction are known as reactants, and the substances that result from the reaction are known as products.

Combination, decomposition, single-replacement, double-replacement, and combustion are the five basic types of chemical reactions.

Analyzing the reactants and products of a specific reaction will allow you to categorize it.

Thus, the correct option is c.

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Your question seems incomplete, the missing options are:

a. products

b. disaccharides

c. reactants

d. water

Answer:

Explanation:

The phosphorous cycle is slower than carbon cycle and nitrogen cycle because phosphorous is found mainly in very small dust particles.

It moves very slowly from the deposits on land and in sediments and then it is transferred to the organism and from organism it is moved more slowly to the soil.

Then from the soil it is transferred again to the sediments. The whole process is very slow and the amount of phosphorus is also very less as compared to carbon and nitrogen cycle.  

I believe the answer in here would be the law of multiple proportions. The law states that whenever the same two elements merge to create more than one compound, the different masses of one element that merge with the same mass of the other element have a ratio that is in whole numbers.

Answer:

law of multiple proportions

Copper chloride forms different hydrates such as dihydrates, hexahydrates, pentahydrates etc. The empirical formula of the compound can be derived from the given mass percentages of copper chloride and water in the compound.

An empirical formula of a compound is used to represent the formula unit of a compound by its constituent elements. The empirical formula is calculated using the number of moles of the elements .

Let the mass percent of A in AB being 40% and the mass percent of B is 60%. Thus, there is 40 g of A in 100 g of AB and 60 g of B. By knowing the atomic masses of A and B we can calculate the number of moles of each element. From this we can get the ratio of them and convert it to the whole number ratios.

By this way we can derive the empirical formula of copper chloride hydrate. The mass percent of water and that of copper chloride gives the number of moles from which we can obtain the empirical formula.

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Answer: will shrink.

Explanation:

The solutions having same osmotic pressure and hence same molar concentration are termed as isotonic. If a solution is of lower osmotic pressure it is called as hypotonic with respect to the concentrate solution. The more concentrated solution is said to be hypertonic with respect to the dilute solution.

When cell is placed in 6% dextrose solution,which is hypertonic to the contents in cell, the water will move from lower osmotic pressure in cell to higher osmotic pressure in 6% dextrose solution through semipermeable membrane and thus the cell will shrink.

The mass of the iron block is calculated using the formula mass = density × volume. With the dimensions provided and density of 7.87 g/cm³, the calculated mass would be approximately 260 g, rounded to three significant figures.

The subject of this question is Chemistry, particularly focusing on the concept of density, which is a measure of how much mass is contained in a given volume. The question involves calculating the mass of an iron block given its dimensions and the known density of iron (7.87 g/cm³). To find the mass, we use the formula mass = density × volume. First, we calculate the volume of the block by multiplying its length, width, and height (2.00 cm × 3.15 cm × 5.25 cm), which gives us 33.075 cm³.

Next, we multiply the volume by the density of iron to get the mass: 33.075 cm³ × 7.87 g/cm³ = 260.48025 g. After applying the rules of significant figures, we round the mass to the appropriate number of significant figures, based on the given density (which is reported to three significant figures), so the final mass of the iron block would be approximately 260 g.

Based on these data,10.81 is the average atomic mass of element b. Therefore, option C is correct.

An atom's mass is its atomic mass. Although the kilogram is the SI measure of mass, the unified atomic mass unit, or dalton, is a common way to express atomic mass. An unbound carbon-12 atom in its ground state has a mass of 112 of a Da.

The total number of protons and neutrons in an isotope's nucleus is referred to as the mass number. This is due to the fact that each proton and neutron has a mass of one atomic mass unit (amu). You may get the mass of the atom by multiplying the total number of protons and neutrons by 1 amu.

From the given table,

Element B has two isotopes i.e.,  

One with a mass of 10.01 and a relative abundance of 19,91,

while the another has a mass of 11.01 and a relative abundance of 80.09.

The average atomic mass

= ( 10.01 × 19.91 ) + ( 11.01 × 80.09)

= 1.99 + 8.817

= 10.81

Thus, option C is correct.

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Your question is incomplete, probably your question was

The table below gives the data that is needed to calculate the average atomic mass of element B. Isotope Atomic mass (amu) Relative abundance (%) B-10 10.01 19.91 B-11 11.01 80.09 Based on these data, what is the average atomic mass of element B? 10.01 10.51 10.81 11.01

Answer is: Exothermic reaction.

Exploding fireworks is chemical change (chemical reaction), because new substances are formed, the atoms are rearranged and the reaction is followed by an energy change (energy is released).

There are two types of reaction: endothermic reaction (chemical reaction that absorbs more energy than it releases) and exothermic reaction (chemical reaction that releases more energy than it absorbs).

The viscosity of a liquid is not how easily i flows, but the measure of its resistance to flowing. Therefore, honey and toothpaste would have the highest viscosity, not the lowest. Water flows easier than oil, so water has the lowest viscosity.

The answer is water.

The liquid having lowest viscosity is water and the correct option is option A.

Viscosity is a physical property that describes the resistance of a fluid to flow. It is a measure of the internal friction within a fluid as its molecules or particles move past each other. In simpler terms, viscosity refers to how "thick" or "sticky" a fluid is.

Viscosity can be thought of as the fluid's resistance to shear or deformation under an applied force. It depends on factors such as the type of fluid, temperature, and pressure. Generally, fluids with stronger intermolecular forces or larger molecular size tend to have higher viscosity.

Thus, the ideal selection is option A.

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An acidic solution contains more hydrogen ions than hydroxide ions, leading to a pH value less than 7.00, due to substances like HCl ionizing in water.

The type of solution that contains more hydrogen ions than hydroxide ions is known as an acidic solution. In such a solution, substances like hydrogen chloride (HCl) ionize in water, producing a higher concentration of hydrogen ions, which are often represented as hydronium ions (H3O+), compared to hydroxide ions (OH-). According to Le Chatelier's principle, the equilibrium in water shifts to the left, leading to a decrease in hydroxide ion concentration. As a result, such solutions have a pH value less than 7.00. Conversely, a basic solution has a higher concentration of hydroxide ions than hydrogen ions, yielding a pH value greater than 7.00.

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Answer : The incorrect option is, 10 kg = 1 g

Explanation :

The following conversion used are,

Conversion of centimeter cube to milliliters :

[tex]1cm^3=1ml[/tex]

Conversion of millimeter to meter :

[tex]1mm=0.001m[/tex]

or, [tex]1000mm=1m[/tex]

Conversion of centigram to gram :

[tex]1cg=0.1g[/tex]

or, [tex]100cg=1g[/tex]

Conversion of kilogram to gram :

[tex]1Kg=1000g[/tex]

or, [tex]10Kg=10000g[/tex]

As per question, only conversion (10 kg = 1 g) is incorrect conversion. While all the conversion are correct.

Hence, the incorrect option is, 10 kg = 1 g

Identify the given and convert it to moles. Identify the desired, and multiply the given number of moles by the mole ratio or equation factor, to produce moles of desired substance. Convert moles of desired substance to the units asked for in the question.

Explanation:

The mole method means that the stoichiometry configuration in a chemical equation is represented as number of moles of each substance.

The following steps are involved in the Mole method:

1) Write the balanced chemical equation.

2) Convert the units of given substance(X) into moles.

3) Using the mole ratio to calculate the moles of wanted substance(Y).

4) Convert moles of wanted substance to the desired units.

For example:

Calculate the mass of MgO?

Mass of MgO = Moles of MgO*molar mass of MgO.

Calculate the moles of Mg = Mass of Mg/Molar mass of Mg.

Moles of Mg = m/24.31.

Answer:

evaporation and distillation

Explanation:

:)

The methods can be used to completely separate a solution containing alcohol and water in evaporation and distillation. Therefore, option A is correct.

The act of selectively boiling and condensing substances from a liquid mixture is known as distillation, or classical distillation. This is often done inside a device called a still.

A liquid is heated to its boiling point to evaporate it, then it is condensed back into a liquid to separate it from impurities or other solutes. This process is known as distillation. Distillation is a common technique used by chemists to sort a mixture of solutes.

Among the many industrial uses of distillation are the production of alcoholic drinks, water purification, and oil refining. Distillation is a physical procedure that removes desired pure compounds from an initial source using heat and other techniques.

Thus, option A is correct.

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Helium which has a chemical formula of He is considered as a noble gas while Nickel which has a chemical formula of Ni is considered as metallic. Although both have different phases but they are both classified under the general category of “Elements”.

answer:

elements

Helium and nickel are elements, which are pure substances that can't be chemically broken down into simpler forms.

Helium and nickel are classified as elements, which are pure substances that make up all kinds of matter. These substances cannot be broken down into simpler substances through chemical changes. Some familiar examples of elements include iron, silver, and gold. There are more than 100 known elements, of which about 90 occur naturally on Earth with the remainder having been created in laboratories.

Answer and Explanation :

Emerging ideas are those ideas which is developed by large number of scientists.

Whereas scientific consensus is the collection of judgement, position and opinion of all the scientists belong to a particular field.

An emerging idea in science is a new concept that is being tested, whereas scientific consensus represents well-established, widely accepted knowledge in the scientific community. Emerging ideas may evolve into scientific consensus after thorough validation, as seen with global warming, or they may be discarded if unsupported by evidence.

An emerging idea in science, often initiated as a hypothesis, is a concept that is relatively new and not yet widely supported or verified with extensive evidence. Over time, through rigorous testing, peer review, and the accumulation of evidence, these emerging ideas may either become part of the accepted body of knowledge or be discarded.

In contrast, scientific consensus represents the collective judgment, position, and opinion of the community of scientists in a particular field of study. Consensus is achieved when the overwhelming majority of scientists agree on a certain view based on a substantial body of evidence. It signifies that the idea or theory is widely accepted and has withstood continued scrutiny and validation, like in the case of global climate change and evolution.

Examples of emerging ideas being tested and challenged over time include research on the relationship between dietary cholesterol and blood cholesterol, and hypotheses regarding dark energy in astronomy. These contrast established consensuses such as evolutionary theory, which is strongly supported by the scientific community and widely considered a fundamental principle of biology.

A neutral atom does not contain any charge because it contains equal number of proton and electron. In this case, we see that the charge is negative 1, so this means that there is 1 more electron than proton for 13C-.

The notation '13C-' denotes a carbon-13 atom that has acquired an extra electron, thus having a net negative charge. Carbon-13 is used in NMR spectroscopy due to its magnetic moment, in contrast to the more common carbon-12 which is NMR-inactive.

The notation 13C- indicates an ion of the carbon isotope with an atomic mass of 13 that has gained an extra electron, leading to a negative charge. The atomic mass (A) of carbon-13 is 13 because it has six protons (which defines it as carbon) and seven neutrons. The negative sign in the upper right-hand corner is not related to the isotope itself but indicates that the atom has an additional electron, giving it a net negative charge. Carbon-12, on the other hand, has six protons and six neutrons, and no charge is indicated when it is in its neutral state.

Carbon-13 is valuable in NMR spectroscopy because unlike the more abundant carbon-12, it has a magnetic moment and is NMR-active, enabling it to provide signals in 13C-NMR spectroscopy. The scarcity and weaker magnetic moment of 13C compared to protons mean that more sample is often required and data from many scans need to be averaged to acquire a clear signal.

Answer: 4-methyl-2-pentyne.

Explanation:

Overall reaction is an example for Nucleophilic substitution (SN2) alkylation of alkynes.

The property which can help us in this case is the electronegativity of atoms. Electronegativity is a measure of how strong an electron will be attracted to that atom. Well, Fluorine is the most electronegative element in the periodic table. Hence the answer is Fluorine.

The element with the given electron configuration is iodine (I).

The element with the ground-state electron configuration kr 5s2 4d10 5p1 is iodine (I), which has an atomic number of 53. Iodine has the electron configuration [Kr]5s²4d¹05p¹. In this configuration, the noble gas core is represented by kr, followed by the valence electrons in the order of 5s², 4d¹0, and 5p¹.

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hard and durable

sterling silver refer to a type of silver which has purity or more correctly finess,  92.5% silver by mass.the remaining 7.5% is copper and because of hardness it is being used in coins jewelry etc

Answer:

The given blank can be filled with harder and more durable.

Explanation:

Sterling silver refers to a silver alloy comprising 92.5 percent by weight of silver and 7.5 percent by weight of other metals, generally copper. Fine silver like 99.9 percent pure silver is comparatively soft, thus in order to increase hardness and strength, silver is generally alloyed with copper. However, sterling silver is vulnerable to tarnishing, and elements other than copper can be utilized in alloys to minimize tarnishings like zinc, germanium, silicon, platinum, and boron.