Chemistry, 10.07.2019 07:30 steven0448

During an experiment, a strip of magnesium (mg) was measured for its length. the scientists completed four trials of measurements. the first scientist measured trials 1 and 2 with a ruler that measures with mm markings. the second scientist measured trials 3 and 4 with a ruler that measures with inches. markings and then converted the data into mm. which options most accurately explain why the scientists’ data were imprecise? (select all that apply) - according to the scenario, the scientists used a piece of lab equipment that is not precise enough to measure the strip of magnesium. - when doing calculations like converting units, the number of significant figures is altered. this can change the level of uncertainty among the trial measurements. - during the recording of data, the first scientist could have converted the trial results incorrectly and caused the data to appear imprecise. - during a lab experiment, having different team members collect trial results could alter the precision of the data based on different individuals’ improper or biased reading of the equipment.

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Answer from: Fsamrai

The only option that fits is the last one — improper and biased measurements.

A scientist should be able to estimate a measurement to a tenth of the smallest scale division. The millimetre ruler would give an uncertainty of ±0.1 mm. The inch ruler would give an uncertainty of ±0.1 in. Since 1 in = 25.4 mm, 0.1 in = 2.54 mm. Thus, the millimetre ruler is more precise than the inch ruler.

Converting units does not change the degree of precision of a measurement.

The first scientist did not convert the units (the second scientist did!).

BUT, having different team members make the observations could introduce uncertainties caused by improper or biased readings of the equipment.

Answer from: Quest

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 : $4x (s) + 3o_{2} (g) \rightarrow 2x_{2}o_{3} (s) h rxn = -600 kj/mol$

equation 2 : $2x (s) + 3cl_{2} (g) \rightarrow 2xcl_{3} (s) h rxn = -800 kj/mol$

equation 3 : $4xcl_{3} (s) + 3o_{2} (g) \rightarrow 2x_{2}o_{3} (s) + 6cl_(2} h rxn = -200 kj/mol$

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 : $4xcl_{3} (s) \rightarrow 4x (s) + 6cl_{2} ( h rxn = (+800) \times 2 kj/mol$

let us add equation 1 & 4

$4x (s) + 3o_{2} (g) \rightarrow 2x_{2}o_{3} (s) h rxn = -600 kj/mol$

$4xcl_{3} (s) \rightarrow 4x (s) + 6cl_{2} ( h rxn = (+1600) kj/mol$

$4xcl_{3} )s) + 3o_{2} \rightarrow 2x_{2}o_{3} (s) + 6cl_{2} (g) h rxn = (+1000) kj/mol$

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

Answer from: Quest

Ithe undersigned only for use your own email and delete any and copies and of the itself and to be there is a good timewhat does a decrease in temperature indicate about the molecules in a sample of liquid water? decreased chemical energy of the moleculesdecreased kinetic energy of the moleculesincreased chemical energy of the moleculesincreased kinetic energy of the moleculeshow does a sample of helium at 15 â°c compare to a sample of helium at 215 k? the helium at 15 â°c has a higher average kinetic energy than the sample at 215 k.the helium at 15 â°c has lower nuclear energy than the sample at 215 k.the helium at 15 â°c has slower-moving atoms than the sample at 215 k.the helium at 15 â°c has smaller atoms than the sample at 215 k.

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During an experiment, a strip of magnesium (mg) was measured for its length. the scientists complete...

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