1) Find the number of molecules in 7.88 g of sulfur
molar mass of S8 = 8*atomic mass of S = 8 * 32.0 g / mol = 256.0 g/mol
Number of moles = mass in grams / atomic mass = 7.88 g / 256.0 g / mol = 0.0308 moles
2) Find the mass of 0.0308 moles of P4
mass = number of moles * molar mass
molar mass of P4 = 4 * atomic mass of P = 4 * 31 g/mol = 124 g/mol
mass of P4 = 0.0308 moles * 124 g/mol = 3.8192g ≈ 3.82 g.
Answer: 3.82 grams of P4 will have the same number of molecules as 7.88 g of S8 (that is 0.0308 moles of molecules)
Answer:
Only II) is correct
Explanation:
I) The red color of the rubies is a physical property of its own structure (wich contains chromium ions)
II)Objects made of silver become tarnished not by a physical property, but as the result of a chemical reaction on the surface of the object made of silver in combination with the sulfur in the air

This changes the color of the object to black, (similar to the iron oxidation)
iii)Boiling is a physical change where a liquid substance absorbs heat in some way (e.g. a flame) and becomes a gas
Answer:

Explanation:
You must calculate the moles of CaCl₂, then convert to formula units of CaCl₂.
1. Molar mass of CaCl₂
CaCl₂ = 40.08 + 2×35.45 = 40.08 + 70.90 = 110.98 g/mol
2. Moles of CaCl₂

3. Formula units of CaCl₂

Answer:233 Joules/K
Explanation:
∆H= 26.5KJmol-1
Kelvin temperature = 34.6 + 273 = 307.6 K
No of moles= 2.7 moles
2.70 mole x 26.5 kJ/mole = 71.55kilojoules
∆S=71.55 kilojoules / 307.6 K = 0.233 kilojoules/ K
Convert to JK-1
0.233 kilojoules/ K x 1000 Joules/kilojoule = 233 Joules/K
So each 19.3g of gold is equivalent to one ml
So if we divide the mass of the gold nugget by the density we can find the volume: 93.5/19.3 = 4.79ml
Hope that helps