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Gennadij [26K]
3 years ago
15

Instructions: Complete each question by choosing or typing in the best answer. To receive the highest score, be sure to leave no

thing blank. When you have completed the test, click the "Grade My Test Now" button at the end of the test. If you run out of time, click the "Save for Me to Complete Later" button. Tests are automatically saved in case of internet disruption. Language: English Español 1) When can a scientific theory be changed? A) when new technology is developed B) after another scientist does an experiment never, once it is a law or theory it is impossible to change after many experiments and much more data has been collected​
Chemistry
1 answer:
babymother [125]3 years ago
5 0
A theory does not change into a scientific law with the accumulation of new or better evidence. A theory will always remain a theory
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5. Write a net ionic equation that occurs in a Na2HPO4/NaH2PO4 buffer solution when: A) a small amount of HCl is added (2 points
labwork [276]

Answer: (A) H_{3}O^{+}(aq) + HPO^{2-}_{4}(aq) \rightarrow H_{2}PO^{2-}_{4}(aq) + H_{2}O(l)

(B) H_{2}PO^{-}_{4}(aq) + OH^{-}(aq) \rightarrow HPO^{2-}_{4}(aq) + H_{2}O(l)

Explanation:

(A) As we know that HCl is a strong acid and when it is added to an aqueous solution then it leads to increase in the concentration of hydrogen ions. And, when an acid or base is added to a solution then any resistance by the solution in changing the pH of the solution is known as a buffer.

This means that addition of buffer into the given solution will not cause much change in the concentration of H_{3}O^{+} in large amount.

As both the buffer components are salt then they will remain dissociated as follows.

       Na_{2}HPO_{4}(aq) \rightarrow 2Na^{+}(aq) + HPO^{2-}_{4}(aq)

 NaH_{2}PO_{4}(aq) \rightarrow Na^{+}(aq) + H_{2}PO^{-}_{4}(aq)

Hence, net ionic equation will be as follows.

       H_{3}O^{+}(aq) + HPO^{2-}_{4}(aq) \rightarrow H_{2}PO^{2-}_{4}(aq) + H_{2}O(l)

(B)  When we add small amount of sodium hydroxide into the solution then there will occur an increase in concentration of hydroxide ions into the solution. But then due to the presence of buffer there will occur not much change in concentration and the acid will get converted into salt.

     NaOH(aq) \rightarrow Na^{+}(aq) + OH^{-}(aq)

The net ionic equation is as follows.

        H_{2}PO^{-}_{4}(aq) + OH^{-}(aq) \rightarrow HPO^{2-}_{4}(aq) + H_{2}O(l)

7 0
3 years ago
Which compound will have the larger rf value on a si02 tlc plate using 10 % ethyl acetate/ hexane as eluent: 3-decanone or 3-dec
Hatshy [7]

The formula of determining the R_f value is:

R_f = \frac{distance travelled by the solute}{distance travelled by the solvent}

where both the distance are measured from the common origin.

10 % ethyl acetate/ hexane means it has 10 % ethyl acetate and 90 % hexane which are non-polar in nature. Hence, the non-polar compound will travel farther in the TLC plate along with the eluent and the polar compound will travel less as they remain attracted to the polar adsorbent SiO_2.

Among 3-decanone and 3-decanol, 3-decanone will have high R_f as it is non-polar.

Among toluene and benzoic acid, toluene will have high R_f as it is non-polar.

Among cyclooctane and cyclooctanone, cyclooctane will have high R_f as it is non-polar.

7 0
4 years ago
What does the Aufbau principle state?
Vikentia [17]
Hello there!

The correct answer is B. Electrons will be added to an atom starting from the lowest possible level or sublevel.

Hope This Helps You!
Good Luck :) 
8 0
4 years ago
Read 2 more answers
Give the name of this alcohol.
solong [7]

Answer:

An alcohol is an organic compound with a hydroxyl (OH) functional group on an aliphatic carbon atom. Because OH is the functional group of all alcohols, we often represent alcohols by the general formula ROH, where R is an alkyl group. Alcohols are common in nature.

Explanation:

3 0
3 years ago
Jill is making lemonade. She mixes together some water, lemon juice, and sugar. The lemonade is classified as a(n) _________. A)
PolarNik [594]

Hello, Thanks for making your post on brainly!

I would say the best answer is C)Mixture

A mixer is made by combining 2 or more elements, but your not making a new element. And there are no chemical reactions happening to make a new element.

Hope this helps. Have a great day.

8 0
3 years ago
Read 2 more answers
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