A calibration curve requires the preparation of a set of known concentrations of CV, which are usually prepared by dieting a stock solution whose concentration is known.
<h3>Answer:</h3>
Strontium (Sr)
<h3>Explanation:</h3>
The condition given in statement is the presence of two valence electron. Hence, first we found the electronic configuration of given atoms as follow;
Rubidium [Kr] 5s¹
Strontium [Kr] 5s²
Zirconium [Kr] 4d² 5s²
Silver [Kr] 4d¹⁰ 5s¹
From above configurations it is cleared that only Strontium and Zirconium has two electrons in its valence shell.
We also know that s-block elements are more reactive than transition elements due to less shielding effect in transition elements hence, making it difficult for transition metals to loose electrons as compared to s-block elements. Therefore, we can conclude that Strontium present in s-block with two valence electrons is the correct answer.
Molecules with a plane of symmetry between the chiral centers are achiral and meso. From the given molecules (Picture attached) only (A) compound 1 is meso.
When compounds possess a plane of symmetry between the chiral centers they are called achiral or meso compounds. Among the given compounds (A) compound 1 have a plane of symmetry. So we can say compound one is a meso or achiral compound. Compounds two, three, and four have no plane of symmetry, as you can see in the structures attached. So all other compounds (compound 2, compound 3, and compound 4) except compound one are not meso or achiral.
You can also learn about meso compounds from the following question:
brainly.com/question/29022658
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Answer : The correct option is, (D) 
Explanation :
(A) 
This reaction is a double displacement reaction in which the cation and anion of two reactants are exchange their places to give two different products.
(B) 
This reaction is a decomposition reaction in which the larger molecule decomposes to give two or more products.
(C) 
This reaction is a neutralization reaction in which an acid and a base react to give a salt and water as a product.
(D) 
This reaction is a redox reaction in which the oxidation and reduction reaction occur simultaneously.
Oxidation reaction is the reaction in which a substance looses its electrons. In this oxidation state increases.
Reduction reaction is the reaction in which a substance gains electrons. In this oxidation state decreases.
In this reaction, magnesium shows oxidation due to change in oxidation number from (0) to (+2) and hydrogen shows reduction due to change in oxidation number from (-1) to (0).
Hence, the correct option is, (D)
Answer:
Chemical weathering
Explanation:
This is a chemical weathering since chemical change is involved. water flows through the rock, it dissolve the rock particles, reacting with the minerals salts in the rock there by producing new substances, ultimately leading to wearing off of the rock particles