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7nadin3 [17]
3 years ago
6

A student takes a stock solution that is 50 mM (solute formula weight is 120.5 g/mol) and prepares a series of solutions. The fi

rst solution is made by diluting 1 mL of the stock in water to a final volume of 15 mL (sample 1). They then take a 2 mL aliquot of sample 1 and dilute in water to a final volume of 25 mL (sample 2). Finally, they take a 1.5 mL aliquot of sample 2 and dilute to a final volume of 250 mL. Calculate the final molar concentration for the analyte in molarity, molality, ppm, and ppb. State any assumptions.
Chemistry
1 answer:
Ira Lisetskai [31]3 years ago
3 0

Answer:

1.6x10⁻⁶M

1.6x10⁻⁶m

0.1928ppm

192.8ppb

Explanation:

The first dilution of the solution is from 1mL to 15mL. The second from 2mL to 25mL and the third from 1.5mL to 250mL. That means molarity is:

50mM =

0.050M * (1mL / 15mL) * (2mL / 25mL) * (1.5mL / 250mL) = 1.6x10⁻⁶M

Molality is defined as the ratio between moles and kg. Assuming the density of the solution is 1kg/L, molality is 1.6x10⁻⁶m

ppm is the ratio between milligrams and Liters:

1.6x10⁻⁶mol / L * (120.5g /mol) * (1000mg / g) = 0.1928mg/L = 0.1928ppm

And ppb = 1000*ppm;

0.1928ppm*1000 = 192.8ppb

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Lena [83]

Answer: a) Ba(ClO_3)_2\rightarrow BaCl_2+3O_2:  Decomposition

b) NaNO_2+HCl\rightarrow NaCl+HNO_2: double displacement

c) CaO+CO_2\rightarrow CaCO_3: Synthesis (Combination)

d) ZnSO_4+Mg\rightarrow MgSO_4+Zn: redox

Explanation:

Decomposition is a type of chemical reaction in which one reactant gives two or more than two products.

Ba(ClO_3)_2\rightarrow BaCl_2+3O_2

A double displacement reaction is one in which exchange of ions take place.

NaNO_2+HCl\rightarrow NaCl+HNO_2

Synthesis reaction is a chemical reaction in which two reactants are combining to form one product.

CaO+CO_2\rightarrow CaCO_3

Redox reaction is a type of chemical reaction in which oxidation and reduction takes place in one single reaction. The oxidation number of one element increases and the oxidation number of other element decreases.

ZnSO_4+Mg\rightarrow MgSO_4+Zn

4 0
3 years ago
The thallium Subscript 81 Superscript 208 Baseline Tl nucleus is radioactive, with a half-life of 3.053 min. At a given instant,
Genrish500 [490]

Answer: (E) 300 bq

Explanation:

Half life is the amount of time taken by a radioactive material to decay to half of its original value.

Radioactive decay process is a type of process in which a less stable nuclei decomposes to a stable nuclei by releasing some radiations or particles like alpha, beta particles or gamma-radiations. The radioactive decay follows first order kinetics.

Half life is represented by t_{\frac{1}{2}

Half life of Thallium-208 = 3.053 min

Thus after 9 minutes , three half lives will be passed, after ist half life, the activity would be reduced to half of original i.e. \frac{2400}{2}=1200, after second  half life, the activity would be reduced to half of 1200 i.e. \frac{1200}{2}=600,  and after third half life, the activity would be reduced to half of 600 i.e. \frac{600}{2}=300,

Thus the activity 9 minutes later is 300 bq.

7 0
3 years ago
Describe how particles of iron (Fe) an oxygen (O2) react to how produce oxide (Fe2O3), also known as rust.
forsale [732]

Answer:

Described by a redox reaction below

Explanation:

Iron(III) oxide is an ionic compound, since it consists of a metal, iron, and a nonmetal, oxygen.

Ionic compounds are formed when metals lose their valence electrons in order to have an octet in their previous shell and donate them to nonmetal atoms, so that nonmetals fill their outer shell to have an octet.

As a result, positive ions (cations) and negative ions (anions) are formed. When iron reacts with oxygen, the following reaction takes place:

4 Fe (s) + 3 O_2 (g)\rightarrow 2 Fe_2O_3 (s)

This is a redox (oxidation–reduction) reaction, since we have electron loss and gain. Four iron atoms lose a total of 12 electrons to obtain a +3 charge in the final compound, while 3 oxygen molecules gain these 12 electrons to become 6 oxide anions with a -2 charge.

4 0
3 years ago
Every bronsted-lowry acid is also a lewis acid True or False
fenix001 [56]
<h2><em>It is True that every bronsted-lowry acid is also a lewis acid </em></h2>

3 0
3 years ago
a beaker of benzene is at room temperature. what is its vapor pressure. Is this vapor pressure large enough to cause the benzene
Serhud [2]

Answer:

(1). The vapor pressure is 91 mmHg at 20°C.

(2). No, benzene will not boil at sea level.

Explanation:

Benzene, C6H6 is an aromatic, liquid compound with with molar mass of 78.11 g/mol and Melting point of 5.5 °C. One of the importance or the uses of benzene is in the making of fibres and plastics.

The vapour pressure of benzene can be gotten from the table showing the vapor pressure of different liquids.

Boiling point can simply be defined as the point or the temperature in which the vapor pressure is the same with the atmospheric pressure.

The atmospheric pressure is 760mmHg, while the vapor pressure at sea level is at the temperature of 15°C which is equal to 71 mmHg( from the table showing the vapor pressure of different liquids).

71 mmHg is not equal to 760 mmHg, thus, at sea level Benzene will not boil.

8 0
3 years ago
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