HNO2+ F- <—> HF + NO2 in the reverse reaction HF is a/an

emmainna [20.7K]

By direct heating of an element with oxygen : many metals and non-. metals burn rapidly when heated in oxygen or air producing their oxides e.g.

3 0

3 years ago

A single penny has a mass of 2.5 g. Abbie and James each measure the mass of a penny multiple times. Which statement about these

const2013 [10]

The question is missing the data sets.

This is the complete question:

A single penny has a mass of 2.5 g. Abbie and James each measure the mass of a penny multiple times. Which statement about these data sets is true?

O Abbie's measurements are both more accurate and more precise than James'.

O Abbie's measurements are more accurate, but less precise, than James'.

O Abbie's measurements are more precise, but less accurate, than James'.

O Abbie’s measurements are both less accurate and less precise than James'.

Penny masses (g)

Abbie’s data

2.5, 2.4, 2.3, 2.4, 2.5, 2.6, 2.6

James’ data

2.4, 3.0, 3.3, 2.2, 2.9, 3.8, 2.9

Answer: first option, Abbie's measurements are both more accurate and more precise than James'.

Explanation:

1) To answer this question, you first must understand the difference between precision and accuracy.

Accuracy is how close the data are to the true or accepted value.


Precision is how close are the data among them, this is the reproducibility of the values.

Then, you can measure the accuracy by comparing the means (averages) with the actual mass of a penny 2.5 g.

And you measure the precision by comparing a measure of spread, as it can be the standard deviation.

2) These are the calculations:

Abbie’s data

Average: ∑ of the values / number of values

Average = [2.5 + 2.4 + 2.3 + 2.4 + 2.5 + 2.6 + 2.6 ] / 7 = 2.47 ≈ 2.5

Standard deviation: √ [ ∑ (x - mean)² / (n - 1) ] = 0.11

James’ data

Average = [2.4 + 3.0 + 3.3 + 2.2 + 2.9 + 3.8 + 2.9] / 7 = 2.56 ≈ 2.6

Standard deviation = 0.53

3) Conclusions:

1) The average of Abbie's data are closer to the accepted value 2.5g, so they are more accurate.

2) The standard deviation of Abbie's data is smaller than that of Jame's data, so the Abbie's data are more precise.

7 0

3 years ago

Read 2 more answers

Liquid hexane

maks197457 [2]

Answer: The mass of $H_2O$ produced is 2.52 g

Explanation:

The number of moles is defined as the ratio of the mass of a substance to its molar mass. The equation used is:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ ......(1)

For hexane:

Given mass of hexane = 1.72 g

Molar mass of hexane = 86.18 g/mol

Putting values in equation 1, we get:

$\text{Moles of hexane}=\frac{1.72g}{86.18g/mol}=0.020mol$

For oxygen gas:

Given mass of oxygen gas = 8.0 g

Molar mass of oxygen gas= 32 g/mol

Putting values in equation 1, we get:

$\text{Moles of water}=\frac{8.0g}{32g/mol}=0.25mol$

The chemical equation for the combustion of hexane follows:

$2C_6H_{14}+19O_2\rightarrow 12CO_2+14H_2O$

By stoichiometry of the reaction:

If 2 moles of hexane reacts with 19 moles of oxygen gas

So, 0.020 moles of hexane will react with = $\frac{19}{2}\times 0.020=0.19mol$ of oxygen gas

As the given amount of oxygen gas is more than the required amount. Thus, it is present in excess and is considered as an excess reagent.

Thus, hexane is considered a limiting reagent because it limits the formation of the product.

By the stoichiometry of the reaction:

If 2 moles of hexane produces 14 moles of $H_2O$

So, 0.020 moles of hexane will produce = $\frac{14}{2}\times 0.020=0.14mol$ of $H_2O$

We know, molar mass of $H_2O$ = 18 g/mol

Putting values in above equation, we get:

$\text{Mass of }H_2O=(0.14mol\times 18g/mol)=2.52g$

Hence, the mass of $H_2O$ produced is 2.52 g

4 0

3 years ago

Which of the following changes will always be true for a spontaneous reaction? (3 points)

Alika [10]

Answer is: - delta G.
The change in Gibbs free energy (ΔG), at constant temperature and pressure, is: ΔG=ΔH−TΔS.
ΔH is the change in enthalpy.
ΔS is change in entropy.
T is temperature of the system.
When ΔG is negative, a reaction (occurs without the addition of external energy) will be spontaneous (exergonic).

3 0

3 years ago

A high jumper jumps 2.09m. If the jumper has a mass of 72kg, what is his gravitational potential energy at the highest point of

Furkat [3]

Si Ko alam hehehehe sorrry men

4 0

3 years ago