Answer : The mass of the water in two significant figures is, 
Explanation :
In this case the heat given by the hot body is equal to the heat taken by the cold body.
where,
= specific heat of iron metal = 
= specific heat of water = 
= mass of iron metal = 32.3 g
= mass of water = ?
= final temperature of mixture = 
= initial temperature of iron metal = 
= initial temperature of water = 
Now put all the given values in the above formula, we get
Therefore, the mass of the water in two significant figures is,
Answer:
0.47dm³
Explanation
Given parameters :
Molarity of NaCl = 6.67M
Number of moles = 3.12mol
Volume of NaCl =?
Volume of NaCl = number of moles/Molarity
Volume of NaCl = 3.12mol/6.67M
Volume of NaCl = 0.47dm³
The arrangement in space and the interatomic distances and angles of the atoms in crystals, usually determined by x-ray diffraction measurements
I think you means the KO2 reacts with H2O. The equation of this reaction is 4KO2+2H2O->4KOH +3O2. The ratio of mole number of O2 and KO2 is 3:4. So the mole number of O2 produced is 0.500/4*3=0.375 mol.
