Answer:
3.74 x 10²² particles
Explanation:
Given parameters:
Mass of compound = 1.43g
Molar mass of compound = 23g
Unknown:
Number of particles of sodium = ?
Solution:
To find the number of particles of Na in the compound, we need to obtain the mass of sodium from the total mass given;
Mass of sodium = 
= 
= 1.43g
Now find the number of moles of this amount of Na in the sample;
Number of moles =
=
= 0.062mole
Now;
1 mole of substance = 6.02 x 10²³ particles
0.062 mole of substance = 0.062 x 6.02 x 10²³ particles
= 3.74 x 10²² particles
D. <span>carbon and hydrogen</span>
Answer: The initial temperature of the iron was 
Explanation:

As we know that,

.................(1)
where,
q = heat absorbed or released
= mass of iron = 360 g
= mass of water = 750 g
= final temperature = 
= temperature of iron = ?
= temperature of water = 
= specific heat of iron = 
= specific heat of water= 
Now put all the given values in equation (1), we get
![-360\times 0.450\times (46.7-x)=[750\times 4.184\times (46.7-22.5)]](https://tex.z-dn.net/?f=-360%5Ctimes%200.450%5Ctimes%20%2846.7-x%29%3D%5B750%5Ctimes%204.184%5Ctimes%20%2846.7-22.5%29%5D)

Therefore, the initial temperature of the iron was 