I had this same question on one of are worksheets is D I can’t really explain it but the answer is D
Answer:
OPTION (A) : Testing a rock sample for gold content
Explanation:
For testing a rock sample of gold content you will need a Chemist. To test the material, the sample is rubbed on black stone which will leave a mark on the stone. This mark is tested by applying aqua fortis i.e nitric acid on the mark. If the mark gets dissolve then the material is not gold. If the mark sustain the it is further tested by applying aqua regia i.e nitric acid and hydrochloric acid which will prove the sample is of gold if it gets dissolve on using hydrochloric acid. The purity of the sample can be checked by differing the concentration of the aqua regia and comparing it with the gold material of the known purity.
<h2>Question:</h2>
A precipitate is a solid that sometimes forms when two liquids combine.
<h2>Answer:</h2>
<u>A</u><u>.</u><u> </u><u>True</u><u> </u>
<h2>Explanation:</h2>
- <u>Because</u><u> </u><u>the</u><u> </u><u>Precipitate</u><u> </u><u>it's</u><u> </u><u>forms</u><u> </u><u>solid</u><u> </u><u>when</u><u> </u><u>two</u><u> </u><u>liquids</u><u> </u><u>combine</u><u> </u><u>to</u><u> </u><u>precipitate</u><u>.</u><u> </u>
<h2><u>#CARRYONLEARNING</u><u> </u></h2><h2><u>#STUDYWELL</u><u> </u></h2>
Answer:
It is heterogeneous as it is made up of visibly different substances or phases.
Answer:
5.41 ×10⁻²²
Explanation:
We were told right from the question that both the Zinc ions and the Zinc oxide adopts a face-centered cubic arrangement.
Then, the number of ZnO molecule in one unit cell = 4
The standard molar mass of ZnO = 81.38g
Avogadro's constant = 6.023 × 10²³ mole
∴
The mass of one unit cell of zinc oxide can be calculated as:
= 
= 5.40461564×10⁻²²
≅ 5.41 ×10⁻²²
∴ The mass of one unit cell of zinc oxide = 5.41 ×10⁻²²
