Atomic Absorption Spectroscopy Questions and Answers

Answer: A

Aspirating from a graduated tube and timing how long a known volume takes gives millilitres per minute directly, which should match the instrument's specification. Flame temperature and blank absorbance report other things, and weighing the drain measures what did not reach the flame. A one-minute check on a quantity the whole measurement depends on is worth doing whenever results look low.

Answer: B

Dividing the volume by the time:

\[ \frac{25}{5} = 5 \ \mathrm{mL/min} \]

giving 5 millilitres per minute, a typical figure. A rate well below specification points at a blockage or a loose connection, and one well above suggests a damaged capillary. A simple ratio that can be checked in a minute is the kind of diagnostic worth building into a routine.

Answer: C

Nitrous oxide-acetylene burns much faster, so its head has a narrower slot to keep the flame from striking back into the burner body - using the wrong head is genuinely dangerous. Alloy, sample admission and wavelength are not the reason. That a safety constraint rather than an analytical one dictates a component's dimensions is worth knowing before heads are interchanged casually.

Answer: D

If the gas velocity falls below the flame's burning velocity, the flame propagates back through the slot into the mixing chamber, which can rupture it. Background emission, lamp arcing and reflections are unrelated. The interlocks, pressure relief bung and correct burner head all exist to prevent it, and the correct shutdown order - extinguishing fuel before oxidant - is part of the same precaution. A limit that survives making every external component ideal is an intrinsic one, and worth knowing for that reason.

Answer: A

Turning off the fuel first leaves the flame to go out for want of something to burn, while cutting the oxidant first can leave a fuel-rich mixture that flashes back. Simultaneous shutdown is not reliably achievable, and the order is not a matter of convenience. A sequence dictated by safety rather than by analytical performance is one to follow exactly, and modern instruments enforce it automatically. Reading the definition literally, rather than recalling a formula, is the reliable route through questions of this shape.