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3 years ago

Match the change to its definition.

1 answer:

5 0

<h3>Answer:</h3><h3 /><h3><em>I </em><em>didnt </em><em>understand</em><em> </em><em>you </em><em>have</em><em> </em><em>already</em><em> </em><em>done </em><em>it </em><em>perfect</em><em> </em></h3>

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If the half-life of a sample of a radioactive substance is 30 seconds, how much would be left after 60 seconds? A. one-fourth B.

Basile [38]

$m=m_{0}*(\frac{1}{2})^{\frac{60}{30}}\\\\
m=m_{0}*(\frac{1}{2})^{2}\\\\
m=\frac{1}{4}m_{0}$

If the half-life of a sample of a radioactive substance is 30 seconds, how much would be left after 60 seconds? <span>A. one-fourth</span>

7 0

3 years ago

Read 2 more answers

In a ________ change, such as a change of state, the substance as a whole changes, but its underlying structure remain the same.

pav-90 [236]

Answer:

Im pretty sure it is chemical change

4 0

3 years ago

A quantity must be divided by multiples of ten when converting from a larger unit to a smaller unit.

seraphim [82]

Answer:It is false

Explanation:

I took a quiz with this question in it and I chose true but I got it wrong

8 0

3 years ago

According to the ideal gas law, increasing the volume of a closed reaction container decreases the thermal energy because the

hichkok12 [17]

Answer:

b is ur answer the temputer does increase

Explanation:

8 0

3 years ago

g A 500. mL solution contains 0.665 M NaC2H3O2 and 0.475 M HC2H3O2. What mass of HCl in grams needs to be added for the solution

77julia77 [94]

Answer:

7.38g HCl

Explanation:

Using H-H equation for acetic buffer:

pH = pKa + log [NaC2H3O2] / [HC2H3O2]

<em>Where pKa is -log Ka = 4.74 and [] could be taken as moles of each compound.</em>

The initial moles of each specie is:

[NaC2H3O2]:

0.500L * (0.665mol/L) = 0.3325moles

[HC2H3O2]:

0.500L * (0.475mol/L) = 0.2375 moles

That means total moles are:

[NaC2H3O2] + [HC2H3O2] = 0.57 moles <em>(1)</em>

And solving H-H equation for a pH of 4.21:

4.21 = 4.74 + log [NaC2H3O2] / [HC2H3O2]

0.29512 = [NaC2H3O2] / [HC2H3O2] <em>(2)</em>

Replacing (1) in (2):

0.29512 = 0.57mol - [HC2H3O2] / [HC2H3O2]

0.29512 [HC2H3O2] = 0.57mol - [HC2H3O2]

1.29512 [HC2H3O2] = 0.57mol

[HC2H3O2] = 0.44 moles

The HCl reacts with NaC2H3O2 producing HC2H3O2, that means you need to add:

0.44 moles - 0.2375 moles =

0.2025 moles of HCl

Using molar mass of HCl (36.45g/mol), to convert these moles to grams:

0.2025 moles * (36.45g/mol) =

8 0

3 years ago