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3 years ago

10

Chemical energy comes from... 1. chemical change 2. physical change

2 answers:

solmaris [256]3 years ago

4 0

Answer:

1

Explanation:

Physical change does not cause chemical energy.

Snowcat [4.5K]3 years ago

4 0

Chemical change Yw btw

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What is the pH of a mixture of 0.042 M NaH2PO4 and 0.058 M Na2HPO4? Hint: The pKa of phosphate is 6.86.

AlekseyPX

Answer:

The pH value of the mixture will be 7.00

Explanation:

Mono and disodium hydrogen phosphate mixture act as a buffer to maintain pH value around 7. Henderson–Hasselbalch equation is used to determine the pH value of a buffer mixture, which is mathematically expressed as,

$pH=pK_{a} + log(\frac{[Base]}{[Acid]})$

According to the given conditions, the equation will become as follow

$pH=pK_{a} + log(\frac{[Na_{2}HPO_{4} ]}{[NaH_{2}PO_{4}]})$

The base and acid are assigned by observing the pKa values of both the compounds; smaller value means more acidic. NaH₂PO₄ has a pKa value of 6.86, while Na₂HPO₄ has a pKa value of 12.32 (not given, but it's a constant). Another more easy way is to the count the acidic hydrogen in the molecular formula; the compound with more acidic hydrogens will be assigned acidic and vice versa.

Placing all the given data we obtain,

$pH=6.86 + log(\frac{0.058}{0.042})$

$pH=7.00$

5 0

3 years ago

Morphine is a well known pain killer but is highly addictive. The lethal dose of morphine varies from person to person based on

Aliun [14]

Answer:

0.252 milimoles

Explanation:

To convert mass of a substance to moles it is necessary to use the molar mass of the substance.

The formula of morphine is C₁₇H₁₉NO₃, thus, its molar mass is:

C: 17*12.01g/mol = 204.17g/mol

H: 19*1.01g/mol = 19.19g/mol

N: 1*14g/mol = 14g/mol

O: 3*16g/mol = 48g/mol.

204.17 + 19.19 + 14 + 16 = <em>285.36g/mol</em>

Thus, moles of 71.891 mg = 0.071891g:

0.071891g × (1mol / 285.36g) = 2.5193x10⁻⁴ moles

As 1 mole = 1000 milimoles:

2.5193x10⁻⁴ moles = <em>0.252 milimoles</em>

7 0

3 years ago

What's your favorite song

Inessa [10]

Run it up by nav and lemonade by dont oliver

3 0

3 years ago

Calculate the ratio of the mass ratio of SS to OO in SOSO to the mass ratio of SS to OO in SO2SO2. Consider a sample of SOSO in

Veronika [31]

Answer:

The ratio of the mass ratio of S to O; in SO, to the mass ratio of S to O; in SO₂, is 2:1

Explanation:

According to the consideration, let us first find the ratio of S and O in both the compounds

For SO:

$\frac{m_{S} }{m_{O} }= \frac{32}{16}\\\\ \frac{m_{S} }{m_{O} }= 2$

Let us express it as

$SO_{\frac{m_{S} }{m_{O} }} = 2$

For SO₂,

Due to two oxygen atoms in the molecule, the mass of oxygen will be taken two times

$\frac{m_{S} }{m_{O} }= \frac{32}{(2)(16)}\\\\ \frac{m_{S} }{m_{O} }= 1$

Let us express it as

$SO_2_{\frac{m_{S} }{m_{O} }}= 1$

Now, for the ratio of both the above-calculated ratios,

$\frac{SO_{\frac{m_{S} }{m_{O} }}}{SO_2_{\frac{m_{S} }{m_{O} }}}=\frac{2}{1}$

The required ratio is 2:1

3 0

2 years ago

What do you call a solid which dissolves?

san4es73 [151]

Answer:

solute

Explanation:

for example sugar salt etc

solute dissolve in solvent

8 0

2 years ago