A scientist uses an uncalibrated pH meter and measures the pH of a rainwater sample four times. A different pH meter was calibrated using several solutions with known pH. The true pH of the rain was found by the calibrated pH meter to be 5.12. What can be said about the level of accuracy and precision of the uncalibrated pH meter? (LO 1.14) (a) The uncalibrated pH meter is accurate and precise. (b) The uncalibrated pH meter is neither accurate nor precise. (c) The uncalibrated pH meter is accurate but not precise. (d) The uncalibrated pH meter is precise but not accurate.

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Hi everyone. This problem reads in an experiment you use an uncalculated mass balance to determine the mass of a sample five times. You then place the sample on a calibrated mass balance and determined its mass to be 4.21 g. What can you conclude about the accuracy and precision of the un calibrated mass balance. Okay, so here we're talking about accuracy and precision and we know that we have five readings and the table shows us the mass for those five readings. So let's go ahead and first define accuracy and precision. Okay, so for accuracy this is going to be related to the mass, the true mass. And so we can say for this experiment accuracy means the value is going to be close to the true mass. Okay. And in this case are true mass is 4.21 g. So it's accurate. If it's close to the true mass precision has to do with variation. So for this experiment for it to be precise, that means there's going to be a small variation between the measurements of the readings. Alright, so let's take a look. So we know that the true mass is 4. g. Okay, so looking at the readings one through five and the masses that accompany those readings, we can see that the measurements are all higher than the true mass. So that means that it is not accurate. These readings are not accurate. Now for precision we also see that there's a large variation between the measurements of the un calibrated mass balance. So that also means it's not precise. So for the answer choices given we want to look for the uncalculated mass balance is neither accurate nor precise and that is reflected in answer choice D. Okay. So answer choice D. Is going to be our correct answer here. It is not accurate nor precise because the readings are not close to the true mass and there's a large variation between the readings. Okay, so that's it for this problem. I hope this was helpful.

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Video transcript

Hi everyone. This problem reads in an experiment you use an uncalculated mass balance to determine the mass of a sample five times. You then place the sample on a calibrated mass balance and determined its mass to be 4.21 g. What can you conclude about the accuracy and precision of the un calibrated mass balance. Okay, so here we're talking about accuracy and precision and we know that we have five readings and the table shows us the mass for those five readings. So let's go ahead and first define accuracy and precision. Okay, so for accuracy this is going to be related to the mass, the true mass. And so we can say for this experiment accuracy means the value is going to be close to the true mass. Okay. And in this case are true mass is 4.21 g. So it's accurate. If it's close to the true mass precision has to do with variation. So for this experiment for it to be precise, that means there's going to be a small variation between the measurements of the readings. Alright, so let's take a look. So we know that the true mass is 4. g. Okay, so looking at the readings one through five and the masses that accompany those readings, we can see that the measurements are all higher than the true mass. So that means that it is not accurate. These readings are not accurate. Now for precision we also see that there's a large variation between the measurements of the un calibrated mass balance. So that also means it's not precise. So for the answer choices given we want to look for the uncalculated mass balance is neither accurate nor precise and that is reflected in answer choice D. Okay. So answer choice D. Is going to be our correct answer here. It is not accurate nor precise because the readings are not close to the true mass and there's a large variation between the readings. Okay, so that's it for this problem. I hope this was helpful.