Answer:
Please, see attached two figures:
- The first figure shows the solutility curves for several soluts in water, which is needed to answer the question.
- The second figure shows the reading of the solutiblity of NH₄Cl at a temperature of 60°C.
Explanation:
The red arrow on the second attachement shows how you must go vertically from the temperature of 60ºC on the horizontal axis, up to intersecting curve for the <em>solubility</em> of <em>NH₄Cl.</em>
From there, you must move horizontally to the left (green arrow) to reach the vertical axis and read the solubility: the reading is about in the middle of the marks for 50 and 60 grams of solute per 100 grams of water: that is 55 grams of grams of solute per 100 grams of water.
Assuming density 1.0 g/mol for water, 10 mL of water is:
Thus, the solutibily is:

Hepta is seven and tetra is four, so option c is your answer
Answer: One formula unit of NaCl consists of one cation, whose chemical symbol is
and one anion whose chemical symbol is 
Explanation:
For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
The cation is formed by the metal sodium which forms
and the anion is formed by non metal chlorine which forms
.
For a formula unit of sodium chloride, the charges have to be balanced , thus the valencies of ions are exchanged and the neutral compound result. Thus
and
combine to form neutral 