A chemist prepares a solution of magnesium fluoride MgF2 by measuring out 0.00598μmol of magnesium fluoride into a 50.mL volumetric flask and filling the flask to the mark with water. Calculate the concentration in /μmolL of the chemist's magnesium fluoride solution. Round your answer to 2 significant digits.


Answer 1


0,12 μmol/L of MgF₂


Preparation of solutions is a common work in chemist's life.

In this porblem says that you measure 0,00598 μmol of MgF₂ in 50,0 mL of water and you must calculate concentration in  μmol/L

You have 0,00598 μmol but not Liters.

To obtain liters you sholud convert mL to L, knowing 1000mL are 1 L, thus:

50,0 mL (1L/1000mL) = 0,05 L of water.

Thus, concentration in  μmol/L is:

0,00598 μmol / 0,05 L = 0,12 μmol/L -The problem request answer with two significant digits-

I hope it helps!

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Which is the most valid reason a group of people might oppose the storage of spent fuel rods in their community?



The most likely reason is that spent fuel bars can infect the community with radiation causing numerous health problems.


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A laboratory scientist wants to analyze the chlorogenic acid content of a 0.5 L sample. He uses an indicator solution and titrates with sodium hydroxide. He finds the equivalence point occurs when he's titrated 9.5 mL of 0.05 M sodium hydroxide. Approximately how much chlorogenic acid is in the sample? 475 umol ® 480 umol © 500 umol 510 umol



There are approximately 475 umol of chlorogenic acid in the sample.


The first step is indentifying the chlorogenic acid structure. As it can be seen in the figure attached, this molecule is a carboxylic acid containing just one carboxyl group. This means, that chlorogenic acid  is a monoprotic acid and it is only able to donate one proton per molecule or one mol of protons per one mol of molecules.

The second step is to balance the titration equation. Considering that sodium hydroxide will generate one mol of hydroxyl ions per mol of salt, we can simplify the equation:

H⁺ + OH ⁻  → H₂O

Therefore, we now know that for each mol of NaOH consumed 1 mol of chlorogenic acid is titrated.

Thus, the last step is calculation the amount of NaOH consumed during the tritation. We can use the following equation:

C = (n)/(V)

In which C is the concentration, n the amount of moles and V the volume.

0,05 M = (n)/(0.0095 L)

The result is that n = 475 umol.

ΔH is always positive for a ...........a. endothermic reaction
b. exothermic reaction
c. spontaneous reaction.
d. nonspontaneous reaction.



a. endothermic reaction


In an endothermic reaction, heat is absorbed from the environment. This leaves the surrounding at a colder temperature compared to the system.

ΔH, the change in enthalpy is assigned a positive sign because the heat energy level of the final state is higher than that of the initial state.

Some examples are mostly dissolution substances in water.

A mixture contains N a H C O 3 together with unreactive components. A 1.68 g sample of the mixture reacts with H A to produce 0.561 g of C O 2 . What is the percent by mass of N a H C O 3 in the original mixture


There is 65% of NaHCO3 in the sample.

The equation of the reaction is;

HA + NaHCO3 -----> NaA + CO2 + H2O

Amount of CO2 formed = mass/molar mass

mass of CO2 = 0.561 g/44 g/mol = 0.013 moles

From the balanced reaction equation;

1 mole of NaHCO3 yields 1 mole of CO2

0.013 moles of Na2CO3 yields 0.013 moles of CO2

Hence, mass of NaHCO3 in the sample = 0.013 moles × 84 g/mol = 1.092 g of NaHCO3

Percentage by mass of NaHCO3 = 1.092 g/1.68 g ×100/1

= 65%

Learn more: brainly.com/question/25150590




The first step here is to write out the reaction showing the chemical reaction between the two chemical species. Thus, we have;

HA(aq) + NaHCO3 --------------> CO2(g) + H20(l) + NaA(aq).

Therefore, the mole ratio is 1 : 1 : 1 : 1 that is go say one mole of HA reacted with one mole of NaHCO3 to give one mole of CO2 and one .ole of NaA.

Hence, the number of moles of CO2 = mass/molar mass = 0.561/44 = 0.01275 moles.

Thus, the number of moles of NaHCO3 = number of moles of CO2 = 0.01275 moles.

Therefore, we have ( 0.01275 moles × 84 g/mol) grams = 1.071 g NaHCO3 in the mixture.

Therefore, the percent by mass of N a H C O 3 in the original mixture = 1.071/1.68 × 100 = 63.75%.

Calculate the pH of the solution formed when 45.0 mL of 0.100M NaOH solution is added to 50.0 mL of 0.100M CH3COOH (Ka for acetic acid = 1.8 x10-5 ).


The study of chemicals and bonds is called chemistry. There are two types of elements are there and these rare metals and nonmetals.

The correct answer is 5.59.

What is PH?

  • pH, historically denoting "potential of hydrogen" is a scale used to specify the acidity or basicity of an aqueous solution.
  • Acidic solutions are measured to have lower pH values than basic or alkaline solutions

The pH of the solution will be due to excessive acid left and the salt formed. Thus, it will form a buffer solution.

The pH of buffer solution is calculated from Henderson Hassalbalch's equation, which is:

pH= pka+log(salt)/(acid)

pka= -log(ka)

pka =-log(1.8*10^(-5)

The moles of acid are taken as:-

moles = M*V


The moles of the base are taken as:-

moles = M*V


moles of acid left is 0.5

Place all the values to the equation:-

pH=4.74+log(4.5)/(0.5) \n=5.69

Hence, the correct answer is 5.69.

For more information about the pH, refer to the link:-



pH of soltion will be 5.69


The pH of the solution will be due to excessive acid left and the salt formed. Thus, it will form a buffer solution.

The pH of buffer solution is calculated from Henderson Hassalbalch's equation, which is:

pH=pKa+log(([salt])/([acid]) )



The moles of acid taken :


The moles of base taken:


The moles of acid left after reaction :


The moles of salt formed = 4.5mmol

Putting values in equation

pH=pKa+log(([salt])/([acid]) )=4.74+log((4.5)/(0.5))=5.69

If you want to melt ice into liquid water, does the ice absorbs heat or release heat? Is this endothermic or exothermic?





This would be an endothermic reaction, due to the fact that the water would be signifigantly warmer then the ice cube, which causes it to melt.


absorbs heat, which makes it endothermic.


Basically melting ice is it in windows or Mac reaction makes the ice absorbs heat energy which causes a change to occur