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bulgar [2K]
3 years ago
11

If an athlete runs at a speed of 12.9 km/hour, how long will it take the athlete to run a marathon (about 42.2 km)? Express your

answer in hours using the correct number of significant figures. Do not enter your answer using scientific notation.
Chemistry
1 answer:
jekas [21]3 years ago
7 0

Answer:

Time = 3.27s

Explanation:

Time = Distance / Speed

Time = 42.2 / 12.9 = 3.2713

When you multiply the number of significant figures in the result is the same as the number with the least significant figures.

In this case 42.2 has 3 significant figures and 12.9 also has 3 significant figures, therefore the answer must have 3 significant figures too.

Time = 3.27 s

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It was calculated that 4.3mL of 0.417 M HCl is required to titrate 11.9 mL of 0.151 M Mg(OH)2. Show evidence 2 HCl(aq) + Mg(OH)2
Lapatulllka [165]

Answer:

See explanation.

Explanation:

Hello,

In this case, for the described chemical reaction:

2 HCl(aq) + Mg(OH)2(aq) → MgCl2(aq) + 2 H2O(l)

We can notice there is a 2:1 molar ratio between the moles of hydrochloric acid and magnesium hydroxide, therefore, at the equivalence point:

n_{HCl}=2*n_{Mg(OH)_2}

And in terms of volumes and concentrations we verify:

V_{HCl}M_{HCl}=2*V_{Mg(OH)_2}M_{Mg(OH)_2}

So we use the given data to proof it:

4.3mL*0.417M=2*11.9mL*0.151M\\1.793=3.594

Therefore, we can conclude the data is wrong by means of the 2:1 mole ratio that for sure was not taken into account. This is also supported by the fact that normalities are actually the same, but the nomality of magnesium hydroxide is the half of the hydrochloric acid normality since the acid is monoprotic and the base has two hydroxyl ions.

Best regards.

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Answer:

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Answer:

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