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alexdok [17]
2 years ago
8

Write the equality and conversion factors, and identify the numbers as exact or give the number of significant figures for which

of the following:A. The Daily Value (DV) for iodine is 150 mcg.B. The nitrate level in well water was 32 ppm.C. Gold jewelary contains 58% gold by mass.D. The price of a litre of milk is $1.65.
Chemistry
1 answer:
alexira [117]2 years ago
8 0
B. Nitrate level in well water was 32 ppm
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The ph of a solution that contains 0.818 m acetic acid (ka = 1.76 x 10-5) and 0.172 m sodium acetate is __________.
crimeas [40]
PH is calculated using <span>Handerson- Hasselbalch equation,

                                      pH  =  pKa  +  log [conjugate base] / [acid]

Conjugate Base  =  Acetate (CH</span>₃COO⁻)
Acid                    =  Acetic acid (CH₃COOH)
So,
                                      pH  =  pKa  +  log [acetate] / [acetic acid]

We are having conc. of acid and acetate but missing with pKa,
pKa is calculated as,

                                     pKa  =  -log Ka
Putting value of Ka,
                                     pKa  =  -log 1.76 × 10⁻⁵

                                     pKa  =  4.75
Now,
Putting all values in eq. 1,
                     
                                     pH  =  4.75 + log [0.172] / [0.818]

                                     pH  =  4.072
4 0
2 years ago
Which of these tasks falls under the responsibility of a forensic scientist?
Varvara68 [4.7K]

Answer:

Training officers in how to properly collect evidence

Explanation:

Forensic science is an interesting branch of science that involves the use of scientific procedures to solve a crime case. It encompasses collection of physical evidence from the crime scene and analyzing it in a laboratory using scientific means.

A forensic scientist is the individual in charge of performing these scientific procedures. His/her major role is to run the scientific analysis of the physical evidence brought in by the officers, however, he/she can also perform the task of training officers in how to properly collect evidence, in order not to damage the evidence or render it invalid for use.

8 0
2 years ago
Balance the following oxidation-reduction reaction: Fe(s)+Na+(aq)→Fe2+(aq)+Na(s) Express the coefficients as integers separated
aliina [53]

Answer:

The answer to your question is: 1, 2, 1, 2

Explanation:

                       1 Fe(s)  + 2 Na⁺(aq)  → 1 Fe²⁺(aq)  + 2 Na(s)

                             Fe⁰   -   2e⁻       ⇒           Fe⁺²        Oxidases

                             Na⁺   +  1 e⁻       ⇒           Na⁰         Reduces

                      1 x ( 1 Fe⁰      ⇒         1 Fe⁺²)      Interchange number of

                      2 x ( 2Na⁺       ⇒       2 Na⁰ )      electrons

6 0
2 years ago
A 0.72-mol sample of PCl5 is put into a 1.00-L vessel and heated. At equilibrium, the vessel contains 0.40 mol of PCl3(g) and 0.
Sonja [21]

Answer:

Equilibrium constant for PCl_5 is 0.5

Equilibrium constant for decomposition of NO_2 is 1.79 \times 10^{-14}

Explanation:

PCl_5 dissociates as follows:

                    PCl_5 \rightleftharpoons PCl_3+Cl_2

initial          0.72 mol     0         0

at eq.     0.72 - 0.40   0.40      0.40

Expression for the equilibrium constant is as follows:

k=\frac{[PCl_3][Cl_2]}{[PCl_5]}

Substitute the values in the above formula to calculate equilibrium constant as follows:

k=\frac{[0.40/1][0.40/1]}{0.32/1} \\=\frac{0.40 \times 0.40}{0.32} \\=0.5

Therefore, equilibrium constant for PCl_5 is 0.5

Now calculate the equilibrium constant for decomposition of  NO_2

It is given that 3.3 \times 10^{-3} \% is decomposed.

NO_2 decomposes as follows:

                                  2NO_2 \rightleftharpoons 2NO + O_2

initial                            1.0 M       0           0

at eq. concentration of  NO_2   is:

[NO_2]_{eq}=1-(0.000066) = 0.999934\ M

[NO]_{eq}=6.6 \times 10^{-5}\ M

[O_2]_{eq}=3.3\times 10^{-5} = 3.3\times 10^{-5}\ M      

Expression for equilibrium constant is as follows:

K=\frac{[NO]^2[O_2]}{[NO_2]^2}

Substitute the values in the above expression

K=\frac{[6.6\times 10^{-5}]^2[3.3 \times 10^{-5}]}{[0.999934]^2} \\=1.79\times 10^{-14}

Equilibrium constant for decomposition of NO_2 is 1.79 \times 10^{-14}

8 0
2 years ago
Groups of atoms that are added to carbon backbones and give them unique properties are known as
Irina-Kira [14]

Answer:

             Groups of atoms that are added to carbon backbones and give them unique properties are known as <u>Functional Groups</u>.

Explanation:

                   In organic chemistry they are called as Functional Group because they are the active part of a molecule. These groups give a unique characteristic to molecule both chemically and physically. Also, each functional group represent a different class of compounds.

Examples:

S No.                          Functional Group                                 Name

1                                   R--X                                             Alkyl Halides

2                                   R--OH                                          Alcohols

3                                  R--NH₂                                         Amines

4                                  R--O--R                                         Ethers

5                                   R--CO--R                                      Ketones

6                                   R--CO--H                                     Aldehydes

7                                  R--CO--OH                                  Carboxylic acids

8                                   R--CO--X                                     Acid Halides

10                                R--CO--NR₂                                 Acid Amides

11                                 R--CO-OR'                                  Esters

3 0
2 years ago
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