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Bogdan [553]
4 years ago
5

Pure water has a hydrogen ion concentration of 1 x 10 (-7) M and a ph of 7. A student measures a basic solution and finds that i

t has a hydrogen ion (H+) concentration of 1 x 10(-3). Explain why the student must have made an error in her measurement.
Physics
1 answer:
Lena [83]4 years ago
6 0

The student must have made an error in her measurement in the concentration of hydrogen ion in the basic solution given. From her measurement, the concentration is  1 × 10−3 M. If we calculate the pH, we get:

pH = -log ( 1 × 10−3) = 3

A pH of 3 does not signifies a basic solution it is in the acidic range. So, the measurement is wrong.

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A marathon runner completes a 42.238 km course in 2 h, 31 min, and 46 s . There is an uncertainty of 29 m in the distance run an
icang [17]

Answer:

The percentage uncertainty in the average speed is 0.10% (2 sig. fig.)

Explanation:

Consider the formula for average speed \bar{v}.

\displaystyle \bar{v} = \frac{s}{t},

where

  • s is the total distance, and
  • t is the time taken.

The percentage uncertainty of a fraction is the sum of percentage uncertainties in

  • the numerator, and
  • the denominator.

What are the percentage uncertainties in s and t in this question?

The unit of the absolute uncertainty in s is meters. Thus, convert the unit of s to meters:

s = \rm 42.238\;km = 42.238\times 10^{3}\;m.

\begin{aligned}\displaystyle \text{Percentage Uncertainty in }s &= \frac{\text{Absolute Uncertainty in } s}{\text{Measured Value of }s}\times 100\% \\ &=\rm\frac{29\; m}{42.238\times 10^{3}\;m}\times 100\%\\ &= 0.0687\%\end{aligned}.

The unit of the absolute uncertainty in t is seconds. Convert the unit of t to seconds:

t = \rm 2\times 3600 + 31\times 60 + 46 = 9106\;s

Similarly,

\begin{aligned}\displaystyle \rm \text{Percentage Uncertainty in }t &= \frac{\text{Absolute Uncertainty in }t}{\text{Measured Value of }t}\times 100\% \\ &=\rm\frac{46\; s}{9106\;s}\times 100\%\\ &= 0.0329\%\end{aligned}.

The average speed \bar{v} here is a fraction of s and t. Both s and t come with uncertainty. The percentage uncertainty in \bar{v} will be the sum of percentage uncertainties in s and t. That is:

\text{Percentage Uncertainty in }\bar{v}\\=(\text{Percentage Uncertainty in } s) + (\text{Percentage Uncertainty in } t)\\ = 0.0687\% + 0.0329\%\\ = 0.010\%.

Generally, keep

  • two significant figures for percentage uncertainties that are less than 2%, and
  • one for those that are greater than 2%.

The percentage uncertainty in \bar{v} here is less than 2%. Thus, keep two significant figures. However, keep more significant figures than that in calculations to make sure that the final result is accurate.

3 0
4 years ago
Темирказык жулдызынын жулдыздык шамасы 2,02, ал Веганын жулдыздык шамасы 0,03. Осылардын кайсысы жарык жане неше есе жарык?
miv72 [106K]

Temirkazık ruled Myanmar value of about 2.02, Vega Funny 0.03. What is the orange light which of these factors times the light?

ლ,ᔑ•ﺪ͟͠•ᔐ.ლლ,ᔑ•ﺪ͟͠•ᔐ.ლ
7 0
3 years ago
A sign is attached to the side of a building as seen below. The sign is attached to a steel rod. A wire connects to the end of t
Kruka [31]

Answer:

500N

Explanation:

50kgx10N/kg

= 500N

3 0
3 years ago
1. Since sleep is so important, we might wonder why people so often fail to get a sufficient amount
ziro4ka [17]

Answer: 9/10

Explanation:

because it's really important and makes you energetic

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Which statement is always true about objects which exert gravitational force on each other? (3 points)
kumpel [21]

Answer:

They have mass is always true.

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