Answer:
b
Explanation:
A pure substance has a constant composition and cannot be separated into simpler substances by physical means. There are two types of pure substances: elements and compounds.
Answer:
not sure if this is the right way to answer this question but PbS is Phosphate-buffered saline (i think)
Explanation:
The alkali metals, which occupy group 1 of the periodic table. This is because the valence shells of these elements have only 1 electron, so easily form an ionic bond with a non-metal compound by donating this. A cation is formed by this donation, since there is one fewer electron orbiting the nucleus than there is in the atomic form - conversely an anion is formed when an atom gains an extra electron to become negatively charged.
Preparing 15 mg/gl working standard solution from a 20 mg/dl stock solution will require the application of the dilution principle.
Recalling the principle:
initial volume x initial molarity = final volume x final molarity
Since we were not given any volume to work with, we can as well just take an arbitrary volume to be prepared. Let's assume that the stock solution is 10 mL and we want to prepare 15 mg/gl from it:
Applying the dilution principle:
10 x 20 = final volume x 15
final volume = 200/15
= 13.33 mL
This means that in order to prepare 13.33 mL, 15 mg/l working standard solution from 10 ml, 20 mg/dl stock solution, 3.33 mL of the diluent must be added to the stock solution.
More on dilution principle can be found here: brainly.com/question/11493179
<em>Explanation:</em>
When 2 moles of sodium hydroxide (NaOH) reacts with 1 mole of phosphoric acid (H3PO4) it gives 1 moles disodium phosphate Na2HPO4 and 2 moles of water.
0.5 molar solution indicates half moles of molecules are present in per ltr solution.
to prepare disodium phosphate you need to dilute phosphoric acid solution to 0.25 molar and add equal quantity of 0.5 molar solution.
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