I'm trying to find the weight of a lemon.

Weight of container= 48 g
Container + pure lemon juice = 184 g (100 ml)
Pure lemon juice= 184g-48= 136g

Does this make sense? Because I thought lemon had around the same density to water... wouldn't that mean my answer should be closer to 100?

And think you are right. I think the density of pure lemon juice is fairly close to that of water. Perhaps the lemon juice you used has seeds? or pulp? I think 1.36 g/mL sounds high to me. In answer to your last question no, it means the answer should be closer to 1.0 g/mL. Or yes, the mass of the 100 mL should be closer to 100 g.

I see from another post that you are asking about the weight. I also note you seem to be using the weight of a lemon and the pure lemon juice almost interchangeably. You know, of course, they are not the same.

Did you weigh the whole lemon? That's not pure lemon juice.
Did you use a good pair of scales and did you read the numbers right?

I juiced the lemons again and got 50 ml and 140g. 8% of citric acid

mol C6H8O7 = 140g x (1 mol/192.14g)
192.14 is the molar mass of C6H8O7
= .7286 mol

c= n/v
.7286 mol/.050 L
=14.57 M

%8 C6H8O7 = 14.57 M x .08
= 1.166 M

I needed to find 8% of citric acid so I just pretended 100% was citric acid and found 8% of it.

V= 50 ml x .08 = 4 mL

citric acid volume/total volume of cleaner

v/v%= 4 mL/500 ml x100

= .8%

Pretty sure this is what I'm supposed to do

Your reasoning is correct in thinking that the weight of a lemon should be similar to that of water since the density of lemons is close to that of water. However, it's important to note that lemon juice is not just water. It contains other substances such as sugars and acids, which can increase its density.

In this case, you have the weight of the container (48g) and the weight of the container with pure lemon juice (184g for 100ml). To find the weight of the pure lemon juice, you subtract the weight of the container from the total weight:

Weight of pure lemon juice = Total weight - Weight of container
Weight of pure lemon juice = 184g - 48g
Weight of pure lemon juice = 136g

So, the weight of the pure lemon juice is 136g. This weight includes the density of the juice itself, which may be slightly higher than that of water due to the other substances present.