Theoretically, yes; practically, it takes some doing. Interplanetary space has very little matter in it, interstellar space less, and intergalactic space less still. If you were to open up a container in space, it would evacuate, and if you were to then seal it again, and bring it back to Earth, then you would have a container with, essentially, empty space.

I like your question.Partly, emptiness is a matter of degree. It's not to hard to have a tiny space the size of the head of a pin that is empty most of the time. It's hard to have a big space that's empty all the time. Emptiness means, to me, having no molecules in the space. I don't know about energy at that level, so I'll just talk about emptiness as 'no molecules'. Air looks empty to us, because we can't see it. It actually has lots of gas molecules, but they're too small and too far apart for us to see. We can show that the air is there by trapping some inside a balloon and mashing on the balloon. The balloon will get smaller, but the invisible something will be pushing back, and so the balloon will burst, to let out the air, if you mash too hard.

When it's foggy, we see something in the air, because some of the fog's water droplets are big enough for us to see.

At the other extreme - fullness - we have solids and liquids that look like they're totally full of stuff, such as ourselves. That's because the molecules are too close together for us to see the tiny spaces between them, so things look full. It's like when look at thin black and white stripes, and if we move far enough away, they'll just look gray, because we can't see the spaces between them at that distance.

So I can take a vacuum pump and attach it to a clear container and pull out most of the air. If the vacuum pump has a pressure gauge on it, it will tell me the pressure is 760 Torr before I turn on the vacuum pump and after it pumps for a while, the vacuum will be 1 milli-Torr or 1 micro-Torr or 1 nano-Torr, or whatever. The contents of the container will look the same to me, because I couldn't see the air and I can't still see anything when most of the air is removed. But there are still a few molecules in the container, and they're whizzing around inside. Also, if we turn off the vacuum pump, molecules will start to come off the sides of the container, and the pressure will start to rise a bit.

We could do calculations to figure out how many gas molecules are in a liter of air at 760 Torr [atmospheric pressure] or 1 milli-Torr or whatever; but maybe you get the idea that it takes a lot of work [the vacuum pump] to make a bit of Nothingness, and molecules will rush into the 'Nothingness' if there's any way for them to do so.

What an interesting question. It is actually something which has puzzled people for a long time. It actually depends on what you define emptiness to be. If you define emptiness to be the absence of matter (as you suggested), then yes it is certainly possible for an empty jar to contain no matter, and thus be empty. There is however a problem. Quantum mechanics has shown that it is possible for particles to actually "pop" in and out of existence. You may have heard these types of discussions in reference to "wave particle duality" which I implore you to explore further. This would imply that although you may very well have a jar devoid of matter for an instant in time, it is entirely possible that at another moment there would be some matter in the jar (even if it is just something like an electron). Does this mean there is something other than matter which constantly fills the jar which facilitates the "popping" in and out of matter? This is an open question.

Keep thinking, maybe one day you will be the one to figure this out.