Reef Chemistry Question of the Day #161 Using a Syringe

[Randy Holmes-Farley]

Reef Chemistry Question of the Day [HASHTAG]#160[/HASHTAG]

I have just drawn tank water into a syringe with a tip (shown below, including a blowup of the barrel). The blue coloration shows where the fluid is.

When I started to draw fluid in, the tip and syringe were empty and the plunger was all the way in. Now I am going to dispense the fluid into my test vial.

How much fluid will be dispensed by pressing the plunger all the way back in?

A. 3.6 mL
B. 2.9 mL
C. 2.2 mL
D. 1.6 mL
E. Cannot be determined because of the air present

Good luck!

.

 

[rockinzebra457]

B 2.9ml

 

[ermartin]

1.6 because in the picture it looks like you removed the tip. but if im supposed to take it on faith the tip is still there ill go with 2.9

 

[StikHedRon]

B) 2.9

 

[Sabellafella]

B

 

[redfishbluefish]

B. This is the basis for Red Sea syringes when doing titrations.....don't need to rid the syringe of air that displaces the volume of the tip

 

[Coelli]

2.9ml and this always drives me crazy.

 

[reef_ranch]

B. It doesn't matter whether there is a tip or not or how big the tip is. The air present is a function of volume of the tip. Smaller tip, less air. Larger tip more air. In all cases, provided the plunger is pulled with the tip submerged, same amount of liquid is drawn into the syringe.

 

[Paul B]

1.6ml

 

[ksanfranfan]

B. 2.9 ml

 

[rayn]

Going with 2.9 as well.

 

[rygh]

I have to go with "3"
Given that setup and picture, I don't see the +/- 0.1, so you need to round off.
Saying 2.9 gives a false sense of precision.

 

[Lynn52]

2.9

 

[Randy Holmes-Farley]

I have to go with "3"
Given that setup and picture, I don't see the +/- 0.1, so you need to round off.
Saying 2.9 gives a false sense of precision.

You don't think you can read that syringe to the nearest tenth of an mL?

 

[Salty1962]

B

 

[twilliard]

It is b
2.9ml

 

[rygh]

You don't think you can read that syringe to the nearest tenth of an mL? That you'd have to read in whole numbers?

Going to whole numbers was really a joke to make a point.
You would only have to round to that if error was +/-1.

But to have fun nitpicking:
The lines on the syringe are 0.2, so estimating half way seems questionable.
Add the general inaccuracy of syringes, plus the imperfect picture,
and I would say YES, 0.1 is not an accurate precision.

"accurate precision"

 

[JimWelsh]

The lines on a 50mL burette, for example, are only every 0.1 mL, but the proper way to read it is to estimate to the nearest 0.01 mL, so even with a less precise syringe, I'd still say that estimating to the nearest 0.1 mL when the graduations are every 0.2 mL is not questionable at all, and very reasonable to do.

Answer is B.

 

[Dtackett]

1.6 because that tiny tip doesn't hold 1.3ml. we can only go based on what we see.

 

[TUSI]

B 2.9