Answer: The final answer is 1,700 J
Explanation: According to first law of thermodynamics:
=Final energy-initial energy=Change in internal energy
q = heat absorbed or released
w = work done by or on the system
w = work done by the system= {Work done by the system is negative as the final volume is greater than initial volume}
q = +500J {Heat absorbed by the system is positive}
w = work done by the system = -300J
U2- 1500J= + 500J --300J
U2= 1700J
1) Focal length
We can find the focal length of the mirror by using the mirror equation:

(1)
where
f is the focal length

is the distance of the object from the mirror

is the distance of the image from the mirror
In this case,

, while

(the distance of the image should be taken as negative, because the image is to the right (behind) of the mirror, so it is virtual). If we use these data inside (1), we find the focal length of the mirror:

from which we find

2) The mirror is convex: in fact, for the sign convention, a concave mirror has positive focal length while a convex mirror has negative focal length. In this case, the focal length is negative, so the mirror is convex.
3) The image is virtual, because it is behind the mirror and in fact we have taken its distance from the mirror as negative.
4) The radius of curvature of a mirror is twice its focal length, so for the mirror in our problem the radius of curvature is:
If the distance between two charges is halved, the electrical force between them increases by a factor 4.
In fact, the magnitude of the electric force between two charges is given by:

where
k is the Coulomb's constant
q1 and q2 are the two charges
r is the separation between the two charges
We see that the magnitude of the force F is inversely proportional to the square of the distance r. Therefore, if the radius is halved:

the magnitude of the force changes as follows:

so, the force increases by a factor 4.
Answer:
10. 36 g ZnCl2
Explanation:
Zn + 2HCl -> ZnCl2 + H2
0.076 mol Zn
1.37 mol HCl
3 mol H2
Limiting reactant: Zn
1 mol Zn -> 1 mol ZnCl2
0.076 mol Zn ->x x= 0.076 mol ZnCl2=10.36 g