In the Minnesota Department of Health set a health risk limit for benzene in groundwater of . Suppose an analytical chemist receives a sample of groundwater with a measured volume of . Calculate the maximum mass in milligrams of benzene which the chemist could measure in this sample and still certify that the groundwater from which it came met Minnesota Department of Health standards. Be sure your answer has the correct number of significant digits.

Answer:

12.99

Explanation:

A chemist dissolves 716. mg of pure potassium hydroxide in enough water to make up 130. mL of solution. Calculate the pH of the solution. (The temperature of the solution is 25 °C.) Be sure your answer has the correct number of significant digits.

Step 1: Given data

Step 2: Calculate the moles corresponding to 0.716 g of KOH

The molar mass of KOH is 56.11 g/mol.

0.716 g × 1 mol/56.11 g = 0.0128 mol

Step 3: Calculate the molar concentration of KOH

[KOH] = 0.0128 mol/0.130 L = 0.0985 M

Step 4: Write the ionization reaction of KOH

KOH(aq) ⇒ K⁺(aq) + OH⁻(aq)

The molar ratio of KOH to OH⁻is 1:1. Then, [OH⁻] = 0.0985 M

Step 5: Calculate the pOH

We will use the following expression.

pOH = -log [OH⁻] = -log 0.0985 = 1.01

Step 6: Calculate the pH

We will use the following expression.

pH + pOH = 14

pH = 14 - pOH = 14 -1.01 = 12.99

Answer:

Apply some dishwashing solution with a white washcloth to the acetone residue and for a few minutes, work in gently from the edges of the spill to the center. Dont rub. Continue until the spill is completely removed.

The correct answer is B. meteorology. The study of weather is called meteorology, derived from the Greek word for "of the atmosphere".

Answer: D (The abundance percentage of each isotope)

Explanation: hope this helps!

Answer:

warm blooded

Explanation:

humans are warm blooded. we cannot change our body temperature as we want to

Answer:

[tex]neutrons_{Ga-69}=38\\\\neutrons_{Ga-71}=40[/tex]

Explanation:

Hello!

In this case, since isotopes of the same element have the same number of protons and electrons but different atomic mass, we can compute the number of neutrons by subtracting the number of protons to the atomic mass of the isotope; thus, for Ga-69 and Ga-71 (rounded up to whole numbers), we obtain:

[tex]neutrons_{Ga-69}=69-31=38\\\\neutrons_{Ga-71}=71-31=40[/tex]

Best regards!

Answer:

the middle and bottom left

Explanation:

one is a positively charged atom, and the other is normal. they are both the same

Answer:

the middle and bottom left .

Answer: Extinction

Animals on the verge of extinction are considered endangered species. Some could argue that the phrasing "threatened" is synonymous to "endangered". Some classify extinction based on if the species is completely wiped out in the wild, or if the species is completely gone (both in the wild and in zoos for instance). Extinction events are not solely due to the changes in atmosphere, but also due to lack of food or habitat, among other possible factors.

Answer:

145.8g

Explanation:

Given parameters:

Number of moles of magnesium hydroxide  = 2.5mol

Unknown:

Mass of Mg(OH)₂  = ?

Solution:

To solve this problem we use the expression below;

  Mass of Mg(OH)₂ = number of moles x molar mass

 Molar mass of Mg(OH)₂ = 24.3 + 2(16 + 1)  = 58.3g/mol

 Mass of Mg(OH)₂ = 2.5 x 58.3  = 145.8g

Answer:

7.13 L of ethanol, CH₃CH₂OH

Explanation:

We'll begin by calculating the number of mole in 2.24 g of ethanol. This can be obtained as follow:

Mass of CH₃CH₂OH = 2.24 g

Molar mass of CH₃CH₂OH = 12 + (3×1) + 12 + (2×1) + 16 + 1

= 12 + 3 + 12 + 2 + 16 + 1

= 46 g/mol

Mole of CH₃CH₂OH =?

Mole = mass / molar mass

Mole of CH₃CH₂OH = 2.24 / 46

Mole of CH₃CH₂OH = 0.049 mole

Next, we shall convert 40 °C to Kelvin temperature. This can be obtained as follow:

T(K) = T(°C) + 273

T(°C) = 40 °C

T(K) = 40 °C + 273

T(K) = 313 K

Finally, we shall determine the volume of ethanol, CH₃CH₂OH in present in the container. This can be obtained as follow:

Pressure (P) = 17.88 KPa

Temperature (T) = 313 K

Number of mole (n) = 0.049 mole

Gas constant (R) = 8.314 L.KPa/Kmol

Volume (V) =?

PV = nRT

17.88 × V = 0.049 × 8.314 × 313

Divide both side by 17.88

V = (0.049 × 8.314 × 313) / 17.88

V = 7.13 L

Thus, 7.13 L of ethanol, CH₃CH₂OH will be present in the container.

Based on the mass of ethanol provided, the mass of liquid ethanol is 1.61 g

The relationship between the gas volume, pressure, temperature and moles is given by the ideal gas equation:

where:

From data provided:

P =  17.88 kPa

V = 3.00 L

T = 40.0 °C = 313 K

R = 0.049 mole

n = ?

n = PV/RT

n =  17.88 * 2/8.314  * 313

n = 0.0137 moles

Mass of ethanol gas = number of moles * molar mass

Mass of gaseous ethanol = 0.0137 mole * 46 g/mol

Mass of gaseous ethanol = 0.63 g

Then:

Mass of liquid ethanol, CH₃CH₂OH = 2.24 - 0.63

Mass of liquid ethanol, CH₃CH₂OH = 1.61 g

Therefore, the mass of liquid ethanol is 1.61 g

Learn more about vapor pressure and mass at:

Answer:

182.70K

Explanation:

Using the general gas equation as follows:

PV = nRT

Where;

P = pressure (atm)

V = volume (L)

n = number of moles (mol)

R = 0.0821 Latm/Kmol

T = temperature (K)

Based on the provided information, P = 5 atm, V = 12L, n = 4 moles, T =?

PV = nRT

5 × 12 = 4 × 0.0821 × T

60 = 0.3284T

T = 60/0.3284

T = 182.70K

Answer:

Sodium carbonate, Na₂CO₃ is the limiting

Explanation:

We'll begin by writing the balanced equation for the reaction between iron (iii) chloride, FeCl₃ and sodium carbonate, Na₂CO₃.

This is illustrated below:

2FeCl₃ + 3Na₂CO₃ → Fe₂(CO₃)₃ + 6NaCl

Next, we shall determine the masses of FeCl₃ and Na₂CO₃ that reacted from the balanced equation. This can be obtained as follow:

Molar mass of FeCl₃ = 56 + (3×35.5)

= 56 + 106.5

= 162.5 g/mol

Mass of FeCl₃ from the balanced equation = 2 × 162.5 = 325 g

Molar mass of Na₂CO₃ = (2×23) + 12 + (3×16)

= 46 + 12 + 48

= 106 g/mol

Mass of Na₂CO₃ from the balanced equation = 3 × 106 = 318 g

SUMMARY:

From the balanced equation above,

325 g of FeCl₃ reacted with 318 g of Na₂CO₃.

Finally, we shall determine the limiting reactant. This can be obtained as follow:

From the balanced equation above,

325 g of FeCl₃ reacted with 318 g of Na₂CO₃.

Therefore, 34.5 g of FeCl₃ will react with = (34.5 × 318)/325 = 33.76 g of Na₂CO₃.

From the calculations made above, we can see clearly that it will take a higher amount (i.e 33.76 g) of Na₂CO₃ than what was given (i.e 25.3 g) to react completely with 34.5 g of FeCl₃. Therefore, Na₂CO₃ is the limiting reactant and FeCl₃ is the excess reactant.

Answer:

Distance, direction and symbol.

Explanation:

Distance, direction and symbol are the three components of the map which make a complete description of a location. On the map, these three components are present which provides information about a specific location on the map. Map is a drawing on the paper that shows the geography of the whole world and provides information in detail.

Answer:

As the oceans absorb more heat, sea surface temperature increases and the ocean circulation patterns that transport warm and cold water around the globe change

Explanation:

Answer:

- Magnesium chloride: MgCl₂.

- Alumina: Al₂O₃.

- Chlorine (VII) oxide: Cl₂O₇.

- Sodium sulfide: Na₂S.

- Calcium oxide: CaO.

Explanation:

Hello!

In this case, according to the naming rules for the given compounds, which state that binary salts have a metal and a nonmetal and oxides contain oxygen, we have:

- Magnesium chloride: MgCl₂.

- Alumina: Al₂O₃.

- Chlorine (VII) oxide: Cl₂O₇.

- Sodium sulfide: Na₂S.

- Calcium oxide: CaO.

Best regards!

Answer: More conservative scientists will try to modify the existing theory to fit the new data. The last answer, the fourth one.

Explanation: I think I had this question before, hope it helps!

Answer:

Centripetal acceleration is related to tangential velocity through ac = v ^ 2 / R

The angular velocity is related to the tangential velocity through ω = v / R

a) ac = (20 m / s) ^ 2/20 m = 20 m / s ^ 2

b) ω = 20 m / s / 20m = 1 rad / s

c) The swept angle is Ф = ω.t = 1 rad / s. 3600 s = 3600 rad

Expressed in turns it is Ф = 3600 rad. 1 turn / (2.π rad) = 573 turn

Explanation:

Answer: C) middle 50 percent of the data

The interquartile range (IQR) spans from the first quartile Q1 to the third quartile Q3.

25% of the data is below Q1 and 75% of the data is below Q3. The gap between the two endpoints consists of 75-25 = 50 percent of the data, or half of the data.

The middle 50 percent of the data. Therefore, option (C) is correct.

The interquartile range (IQR) shows the spread or dispersion of a dataset. It is calculated as the difference between the third quartile (Q3) and the first quartile (Q1) in a sorted dataset. The first quartile (Q1) is the value below which 25 percent of the data falls, and the third quartile (Q3) is the value below which 75 percent of the data falls.

The interquartile range captures the range of the central 50 percent of the data. It provides a measure of the variability or spread of the middle portion of the dataset while excluding the influence of extreme values or outliers.

Learn more about interquartile range, here:

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Answer:

14 hrs.

Explanation:

From the question given above, the following data were obtained:

Time (t) = 42 hrs

Original amount (N₀) = 4.32 g

Amount remaining (N) = 0.54 g

Half-life (t½) =…?

Next, we shall determine number of half-lives required for 4.32 g of the isotope to decay to 0.54 g. This can be obtained as follow:

Original amount (N₀) = 4.32 g

Amount remaining (N) = 0.54 g

Number of half-lives (n) =?

N = 1/2ⁿ × N₀

0.54 = 1/2ⁿ × 4.32

Cross multiply

0.54 × 2ⁿ = 4.32

Divide both side by 0.54

2ⁿ = 4.32 / 0.54

2ⁿ = 8

Express 8 in index form with 2 as the base

2ⁿ = 2³

n = 3

Thus, it took 3 half lives for 4.32 g of the isotope to decay to 0.54 g.

Finally, we shall determine the half-life of the isotope. This can be obtained as follow:

Time (t) = 42 h

Number of half-lives (n) = 3

Half-life (t½) =

n × t½ = t

3 × t½ = 42

Divide both side by 3

t½ = 42 / 3

t½ = 14 hrs

Thus, the half-life of the isotope is 14 hrs

Answer:

False, they can interact without touching

Answer:

QhhjjgDjKfxockzgnx

Explanation:

DjiDfj,jzo

Answer:

2.18 × 10⁷ Au atoms

Explanation:

Step 1: Calculate the diameter of a gold atom

The diameter is twice the radius.

d = 2 × r = 2 × 144 pm = 228 pm

Step 2: Convert "d" to meters

We will use the conversion factor 1 m = 10¹² pm.

228 pm × 1 m/10¹² pm = 2.28 × 10⁻¹⁰ m

Step 3: Convert the total distance to be covered (D) to meters

We will use the conversion factor 1 m = 10³ mm.

4.97 mm × 1 m/10³ mm = 4.97 mm × 10⁻³ m

Step 4: Calculate the number of atoms of gold required

We will divide the total distance by the diameter of 1 atom of gold.

D/d = 4.97 mm × 10⁻³ m/2.28 × 10⁻¹⁰ m = 2.18 × 10⁷

Answer:

[NH₄NO₃] at D → 0.279 M

Explanation:

This exercise involves a series of dilutions one after the other.

First of all, we calcualte ammonium nitrate's concentration at A.

15.71 g . 1 mol/ 80 g = 0.196 mol / 0.150 mL = 1.31 M

At B → 1.31 M . 20 mL/ 75 mL = 0.349  M

At C →  0.349 M . 15 mL / 25 mL = 0.209 M

[NH₄NO₃] at B = 0.349 M

[NH₄NO₃] at C = 0.209 M

So let's calculate the new moles

In 1 mL of B we have 0.349 mmoles

In 10 mL of B we have 3.49 mmoles

In 1 mL of C we have 0.209 mmoles

In 10 mL of C we have 2.09 mmoles

Volume of D = 10 ml + 10ml = 20 mL

Total mmmoles = 3.49 mmoles + 2.09 mmoles = 5.58 mmoles

[NH₄NO₃] at D = 5.58 mmoles / 20mL → 0.279 M

Answer:

a. Remaining at rest requires the use of ATP.

Explanation:

The resting membrane potential is maintained by the sodium-potassium pump. The sodium potassium pump does this by actively pumping sodium ions out of the cell and potassium ions inside the cell in a ratio of 3:2. This movement of ions by the sodium-potassium pump is against their concentration gradient. In a neuron at rest, there are more sodium ions outside the cell than there are inside the cell. Also, there are are more potassium ions inside the cell than there are outside the cell. However, there are ion channels through which these ions enter and leave the cell. Sodium ion channels allow sodium to enter the cell following its concentration gradient, whereas, potassium ion channels allow potassium to leave the cell following its concentration gradient. However, more potassium ions leave the cell than do sodium ions enter the cell because of the higher permeability of the cell to potassium ions.

In order to maintain the resting membrane potential, the sodium potassium pump powered by the hydrolysis of an ATP molecules pumps sodium ions out of the cell and potassium ions into the cell.

Therefore, the correct option is A, as ATP is needed by the sodium-potassium pump in order to maintain the resting membrane potential.

Answer:

Molecules

Explanation:

Answer: 1. Oxygen is the the limiting reactant.

2. 7.52%

Explanation:

The balanced chemical equation is:

[tex]2H_2(g)+O_2(g)\rightarrow 2H_2O(g)[/tex]  

To calculate the moles :

[tex]\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}[/tex]    

[tex]\text{Moles of} H_2=\frac{30.0g}{2g/mol}=15.0moles[/tex]

[tex]\text{Moles of} O_2=\frac{5.29g}{32g/mol}=0.165moles[/tex]

According to stoichiometry :

1 mole of [tex]O_2[/tex] require  = 2 moles of [tex]H_2[/tex]

Thus 0.165 moles of [tex]O_2[/tex] will require=[tex]\frac{2}{1}\times 0.165=0.331moles[/tex]  of [tex]NH_3[/tex]

Thus [tex]O_2[/tex] is the limiting reagent as it limits the formation of product and [tex]H_2[/tex] is the excess reagent.

2.  [tex]\text{Moles of} H_2=\frac{9.93g}{2g/mol}=4.96moles[/tex]

[tex]\text{Moles of} H_2O=\frac{6.72g}{18g/mol}=0.373moles[/tex]

As 2 moles of [tex]H_2[/tex] give = 2 moles of [tex]H_2O[/tex]

Thus 4.96 moles of [tex]H_2[/tex] give =[tex]\frac{2}{2}\times 4.96=4.96moles[/tex]  of [tex]H_2O[/tex]

percentage yield = [tex]\frac{\text {actual yield}}{\text {theoretical yield}}=\frac{0.373}{4.96}\times 100=7.52\%[/tex]

Thus the percent yield for the reaction is 7.52%