Answer:
56°
Explanation:
First calculate 

The interplanar spacing can be calculated from:

The diffraction angle is determined from:

Solve for 

The diffraction angle is:

Answer:
1. negative
2. positive
3. neutral
Explanation:
Ok so it looks like they are asking for the charge (positive, negative, or neutral) of each thing
So for 1, it would be negative, because it's pointing to an electron. Electrons always have a negative charge.
So for 2, it would be positive, because it's pointing to a proton. Protons always have a positive charge
So for 3, it would be neutral, because it's pointing to a neutron. Neutrons always have a neutral charge.
One-
The 6 is the only significant figure.
Answer:

Explanation:
Hello,
In this case, we can consider that the given heat of combustion is indeed the heat of reaction since it corresponds to the combustion of propane, which is computed by using the heat formation of all the involved species as shown below:

Thus, since the heat of formation of gaseous carbon dioxide is -393.5 kJ/mol, water -241.8 kJ/mol and oxygen 0 kJ/mol, the heat of formation of propane is:

Best regards.