Which of the following statements correctly describe metalloids?
- Metalloids are elements that have both metal and nonmetal properties
- Metalloids are metals that do not lose
-Metalloids are metals that do not attract electrons 
-Metalloids are elements that only have metal properties Save

Answer:  the correct choice is d) 100000 organisms in 0.5 miles.

Explanation: Population density is directly proportional to the number of species(organisms) and inversely proportional to the land area.

population density = number of organisms/land area

Let's plug in the values for all the choices and see which one gives greatest population density.

a) population density = [tex]\frac{125000}{2.5}[/tex]  = 50000

b) population density = [tex]\frac{13000}{1.0}[/tex]  = 13000

c) population density = [tex]\frac{150000}{4.0}[/tex]  = 37500

d) population density = [tex]\frac{100000}{0.5}[/tex]  = 200000

From above calculations, the greatest population density(200000 organism per mile) is for the last choice.

So, the correct choice is d) 100000 organisms in 0.5 miles.

Many toxic manufacturing compounds are securely disposed of through the means of high-temperature combustion. However mercury is not "annihilated" when coal comprising mercury impurities is scorched. This is happening because when the mercury in the carbon (coal Hg) is burned it changes into a gas which is emitted into the atmosphere.

Lewis electron dot diagrams represent valence electrons around atomic symbols, aiding in predicting bonding capabilities. Valence electrons' importance in chemical reactivity is highlighted through electron-dot symbols in Lewis diagrams.

Lewis electron dot diagrams use dots to represent valence electrons around an atomic symbol. These dots are arranged to the right and left, above, and below the symbol, indicating the valence electrons. For example, in the Lewis structure for hydrogen, it is represented by a single dot.

Valence electrons are crucial in determining an atom's reactivity and bonding capabilities. Electron-dot symbols help predict the number of bonds an element can form in a compound. In Lewis diagrams, dots represent the valence electrons, while lines denote bonds formed between atoms.

Final answer:

Hydrogen was discovered in England by Henry Cavendish in 1766. While this discovery was unrelated to celestial observations as in the case of helium, hydrogen is the most abundant element in the universe and essential in the composition of stars.

Explanation:

The element hydrogen was discovered in England, not in the context of celestial observations but as an earthly element. The first recognized discovery of hydrogen is attributed to the English scientist Henry Cavendish in 1766. Cavendish identified hydrogen as a distinct species by performing experiments in which he reacted metals with strong acids to produce a gas. However, its importance and the role it plays in the universe were not completely understood at that time. Later discoveries, like that of helium in the sun's spectrum, showcased the extensive presence of elements like hydrogen in outer space, being central to the composition of stars like our Sun.

Although the student's question seems slightly mixed up with the discovery of helium, it provides a good opportunity to explore not only the terrestrial elements but also those found in the cosmic environment. Hydrogen is the most abundant element in the universe and plays a vital role in the constitution of stars and many compounds on Earth.

Answer:

+1

Explanation:

Heat capacity is the amount of heat required to raise the temperature of the system by 1 degree Celsius. Thus the specific heat capacity of zinc is 0.0071 calorie / (g °C).

Enthalpy term is basically used in thermodynamics to show the overall energy that a matter have. Mathematically, Enthalpy is directly proportional to specific heat capacity of a substances.

Mathematically,

Enthalpy=mass of solution ×specific heat capacity of solution ×Change in temperature.

Heat released by the water = 55.9 g × 1 calorie/ (°C g) ×(99.2 - 96.9 )°C

Heat absorbed by the zinc metal =  23.9 g ×specific heat ×(96.9 - 21.1) °C

Heat absorbed by zinc metal = heat released by water

23.9 × Specific heat of zinc metal ×75.8 = 55.9 ×1 ×2.3

specific heat of zinc metal = 128.57 ÷1811.62 = 0.0071 calorie / (g °C)

Thus the specific heat capacity of zinc is  0.0071 calorie / (g °C)

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Answer: B. electrons orbit the nucleus in distinct circular paths

Explanation: Electrons are found in shells or orbitals that surround the nucleus of an atom.

At a consistent leakage rate of 1.2 mL/hour, a container will lose 0.2016 liters of water over the span of a week.

If water is leaking from a container at a rate of 1.2 mL/hour, we can calculate the total amount of water lost in a week by first understanding the total hours in a week and then multiplying this by the rate of leakage.

A week consists of 7 days, and each day has 24 hours, making the total hours in a week 168 hours. Given the rate of 1.2 mL/hour, we multiply this rate by the total hours to find the total volume of water lost over the week:

1.2 mL/hour * 168 hours = 201.6 mL

To convert this volume into liters, we remember that 1000 mL equals one liter. Therefore, dividing 201.6 mL by 1000 gives us the volume in liters:

201.6 mL / 1000 = 0.2016 liters

Thus, at a rate of 1.2 mL/hour, a total of 0.2016 liters of water will be lost in a week.

The elements in a given period (horizontal row) have the same number of electron shells in their atoms.

The horizontal row in the modern periodic table is called period. All elements placed in a period have the same number of electron shells. Each next element in a period exceed one proton and so has less metallic character than its precursor.

The atomic number increases on moving left to right in a period that tells that number of electrons and protons increases in an atom. As in a period, elements have filled the same electron shells, but an increase in the number of electrons in the same shell causes an increase in the effective nuclear charge. Therefore, the atomic radius of an atom of the elements decreases in a period.

Therefore, the elements in the same period have the same number of electron shells. For example, all elements of the second period have only two electron shells.

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The question does not provide specific data for different sites or collection days to determine where swimming would be unsafe. However, if E. coli concentration exceeds 200 colonies per 100 mL water, it's unsafe. Regular sampling and testing is crucial to ensure water safety for recreational activities.

The information provided does not include specific data on the concentration of E. coli colonies at different sites or at different collection days, which makes it impossible to identify the days or sites where it would have been unsafe to swim, tube, or raft. However, the concept of unsafe concentrations of E. coli in water can be discussed. The U.S. Environmental Protection Agency (EPA) sets enforceable concentration values for primary contaminants, and these are known as Maximum Contaminant Levels (MCLs). For E. coli, a concentration exceeding 200 colonies per 100 mL is deemed unsafe.

Water sampling and testing for the presence of E. coli is a common microbial testing procedure. In a simplified process, the sample is diluted in lactose broth tubes at different volumes and then incubated. If E. coli is present, it ferments the lactose, causing a color change in the broth. This method helps to estimate the probable number of bacteria per 100 mL of water.

Maintaining good personal hygiene and avoiding untreated water in developing nations is crucial to preventing E. coli infections. Ensuring the safety of recreational water activities involves continuous monitoring and testing of water samples to prevent potential health hazards related to excessive E. coli concentration in the water. In the absence of monitoring and testing, any water body could potentially be unsafe for swimming, tubing, and rafting.

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Answer is: B. beta particles.

Nuclear reaction: ¹⁴C → ¹⁴N + e⁻ + νe (electron antineutrino).

In beta minus decay (atomic number Z is increased by one, from 6 in carbon to 7 in nitrogen) neutron is converted to a proton and an electron and an electron antineutrino.

Beta decay is radioactive decay in which a beta ray and a neutrino are emitted from an atomic nucleus.

Answer: True

Explanation: The Periodic Table is an orderly grouping chemical elements known to scientists. This table includes the name of each element, its symbol, atomic mass (weight), and electron distribution. The first letter of each chemical symbol is capitalized.

Final answer:

The correct answer "atom". The smallest unit that can maintain the properties of an element is an atom. Atoms are composed of electrons, protons, and neutrons, with the number of protons determining the element type. Atoms are the key to understanding elemental properties.

Explanation:

The smallest unit that can exist as an element and still maintain the properties of that element is a(n) atom. An atom is the foundational building block of all matter, and it retains all the characteristics of the element. By definition, atoms are composed of subatomic particles: electrons (negative charge), protons (positive charge), and neutrons (neutral). These particles are what give the atom its properties. The number of protons in an atom’s nucleus specifically determines the type of element it is.

Atoms are extremely small, typically around 100 picometers in size, and their behavior is heavily influenced by quantum mechanics. This means that classical physics, which might treat particles like billiard balls, does not accurately predict atomic behavior. Atoms are the smallest units that maintain the properties of an element, making it the correct answer (D).

Final answer:

To determine the moles of sucrose available, the molar mass of sucrose is calculated and used to convert the given mass of sucrose to moles, resulting in approximately 0.0292 moles.

Explanation:

To calculate the number of moles of sucrose available for the combustion reaction, first, we need to find the molar mass of sucrose (C₁₂H₂₂O₁₁). By adding the atomic masses of carbon (12 atoms × 12.01 g/mol), hydrogen (22 atoms × 1.008 g/mol), and oxygen (11 atoms × 16.00 g/mol), we can determine the molar mass of sucrose to be approximately 342.3 g/mol. Using the mass of sucrose given, we can calculate the number of moles of sucrose as follows:

Therefore, there are approximately 0.0292 moles of sucrose available for the reaction.

Answer:

in shorter terms, the answer is B. CH3COOH + H2O CH3COO- + H3O+

Explanation:

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To find the H+ concentration of an ammonia solution with a pH of 9.15, we use the inverse logarithm of the negative pH value, which gives a H+ concentration of 7.08  imes 10^-10 M.

If the pH of a 0.35 M ammonia solution is 9.15, we can calculate the H+ concentration using the pH formula. The formula for pH is pH = -log[H+], where [H+] represents the concentration of hydrogen ions in moles per liter (M). To find [H+], we take the inverse logarithm (antilog) of the negative pH value:

[H+] = 10-pH

Plugging in the pH value given:

[H+] = 10-9.15 = 7.08  imes 10-10 M

Therefore, the concentration of H+ ions in the ammonia solution is 7.08  imes 10-10 M.