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larisa86 [58]
2 years ago
8

2 human activities that contribute to runoff into water systems

Chemistry
1 answer:
Elodia [21]2 years ago
6 0
Urinating respiration crying flooding
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A first-order reaction has a half-life of 20.0 minutes. Starting with 1.00 × 1020 molecules of reactant at time t = 0, how many
zalisa [80]

Half-life time of a reaction is time at which reactant concentration becomes half of its initial value.

Half-life of the first order reaction is 20 min. Rate constant can be calculated as follows:

K=\frac{0.6932}{t_{1/2}}=\frac{0.6932}{20 min}=0.03466 min^{-1}

The rate expression for first order reaction is as follows:

k=\frac{2.303}{t}log\frac{A_{0}}{A_{t}}

initial number of molecules of reactant are 10^{20}, time is 100 min thus, putting the values to calculate number of reactant at time 100 min,

0.03466 min^{-1}=\frac{2.303}{100 min}log\frac{[10^{20}]}{A_{t}}

On rearranging,

\frac{10^{20}}{A_{t}}=31.988

Or,

A_{t}=3.13\times 10^{18}

Therefore, number of molecules unreacted will be 3.13\times 10^{18}

7 0
3 years ago
Value of an extensive property
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The value of an intensive property may vary with time and its position within the system. Examples of intensive properties include temperature, velocity, mass density, specific volume, and specific energy. An extensive property does not have a value at a point, and its value depends on the extent or size of the system.

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3 years ago
The degree to which a measurement approaches a standard value is _____. accuracy
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Refer to the illustration above. Which time period shows exponential growth of the population
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4 0
3 years ago
How many joules of heat are removed from a 21.0 g sample of water if it is cooled from 34.0°C
yaroslaw [1]

Answer:

527.184 J of heat is removed from a 21 g water sample if it is cooled from 34.0 ° C to 28.0 ° C.

Explanation:

Calorimetry is the measurement and calculation of the amounts of heat exchanged by a body or a system.

When the heat added or removed from a substance causes a change in temperature in it, this heat is called sensible heat.

In other words, the sensible heat of a body is the amount of heat received or transferred by a body when it undergoes a change in temperature without there being a change in physical state (solid, liquid or gaseous). The equation that allows to calculate this heat exchange is:

Q = c * m * ΔT

Where Q is the heat exchanged by a body of mass m, constituted by a substance of specific heat c and where ΔT=Tfinal-Tinitial is the change in temperature.

In this case:

  • c= 4.184 \frac{J}{g*C}
  • m=21 g
  • ΔT=Tfinal-Tinitial=28 °C - 34 °C=-6 °C

Replacing:

Q= 4.184 \frac{J}{g*C} * 21 g* (-6 C)

Q= - 527.184 J

To lower the temperature, heat has to be given, for that the final temperature must be lower than the initial temperature; and it receives the name of transferred heat and has a negative value, as in this case.

<u><em> 527.184 J of heat is removed from a 21 g water sample if it is cooled from 34.0 ° C to 28.0 ° C.</em></u>

4 0
3 years ago
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