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3 years ago

Which terms are used to identify pure substances?

Chemistry

1 answer:

ratelena [41]3 years ago

6 0

Answer:

mabey c or d

Explanation:

color, odor, density, melting temperature, boiling temperature, and solubility are examples of physical properties. Physical properties can be used to identify a pure substance.

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why do you think that sodium chloride has to be heated to 800c before melting, but candle wax will start to melt at 50c?

RideAnS [48]

Answer:

Sodium chloride is an ionic compound which makes it stronger and have a higher melting and boiling point. Candle wax is a covalent compound so it has a low melting point.

Explanation:

<h2><u><em>PLEASE MARK AS BRAINLIEST!!!!!</em></u></h2>

5 0

3 years ago

The initial reaction rate for the elementary reaction 2A + B → 4C was measured as a function of temperature when the concentrati

Artist 52 [7]

Complete Question

The complete question is shown on the first uploaded image

Answer:

a) The activation energy is 124.776 $\frac{kJ}{mole}$

b) The frequency factor is 1.77 × $10^{18}$

c) The rate constant is 0.00033 $(\frac{dm^{3} }{mole} )^{2}$ $\frac{1}{s}$

Explanation:

From the question the elementary reaction for A and B is given as

2A + B → 4C

The rate equation the elementary reaction is

- $r_{A}$ = $k$ $[A]^{2}$ $[B]$

= $k[2]^{2}[1.5]$

= 6k

$k = \frac{-r_{A} }{6}$

When temperature changes, the rate constant change an this causes the rate of reaction to change as shown on the second uploaded image.

The relationship between temperature and rate constant can be deduced from these equation

$k = Aexp(-\frac{E_{a} }{RT} )$

taking ln of both sides we have

$lnk =ln A - (\frac{E_{a} }{R}) \frac{1}{T}$

Considering the graph for the rate constant $ln k$ and $(\frac{1}{T} )$ the slope from the equation is $-(\frac{E_{a} }{R})$ and the intercept is $ln A$

From the given table we can generate another table using the equation above as shown on the third uploaded image

The graph of $ln k$ vs $(\frac{1}{T} )$ is shown on the fourth uploaded image

From the graph we can see that the slope is $-(\frac{E_{a} }{R} ) = - 15008$

Now we can obtain the activation energy $E_{a}$ by making it the subject in the equation also generally R which is the gas constant is $8.145 \frac{J}{kmole}$

$E_{a} = 15008 × 8,3145\frac{J}{molK}$

$= 124\frac{KJ}{mole}$

Hence the activation energy is $= 124\frac{KJ}{mole}$

b) From the graph its intercept is $ln A = 42.019$

$A = exp(42.019)$

$=1.77 × 10^{18}$

Hence the frquency factor A is $=1.77 × 10^{18}$

c) From the equation of rate constant

$lnk =ln A - (\frac{E_{a} }{R}) \frac{1}{T}$

We have

$ln k = 42.019 - 15008 * (\frac{1}{300} )$

$k = 0.00033(\frac{dm^{3} }{mole} )^{2} \frac{1}{s}$

Hence the rate constant is $k = 0.00033(\frac{dm^{3} }{mole} )^{2} \frac{1}{s}$

6 0

3 years ago

The heat of vaporization for water is 40. 7 kJ/mol. How much heat energy must 150. 0 g of water absorb to boil away completely?

netineya [11]

The heat absorbed by the water sample for vaporization has been 6,105 kJ. Thus, option D is correct.

The heat of vaporization has been the amount of heat required to vaporize 1 gram of liquid.

The heat required for the vaporization has been given as:

$Q=m\Delta H_{vap}$

<h3 /><h3>Computation for the Heat of vaporization</h3>

The heat of vaporization of water has been given as, $\Delta H_{vap}=40.7\;\rm kJ/mol$

The mass of water sample has been, $m=150\;\rm g$

Substituting the values for the heat energy absorbed, <em>Q:</em>

<em />

<em /> $Q=150\;\times\;40.7\;\rm kJ\\
\textit Q=6,105\;kJ$

The heat absorbed by the water sample for vaporization has been 6,105 kJ. Thus, option D is correct.

Learn more about heat of vaporization, here:

brainly.com/question/2427061

3 0

3 years ago

At which electrode does oxidation occur in a

Trava [24]

The right answer for the question that is being asked and shown above is that: "(2) the cathode in a voltaic cell and the anode in an electrolytic cell." At the status of electrode does oxidation occur in a voltaic cell and in an electrolytic cell is that the cathode in a voltaic cell and the anode in <span>an electrolytic cell</span>

5 0

4 years ago

Read 2 more answers

Which letter? Thanks in advance!

Mashcka [7]

Answer: b

Explanation:

7 0

3 years ago