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3 years ago

Which of the following statements is not part of Dalton's atomic theory? ( points)

1 answer:

4 0

The answer is "different atoms come together to form an element"- it is wrong because elements are made up of the same atoms.

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Calculate the pH of each of the following solutions. a. 0.100 M propanoic acid (HC3H5O2, Ka 1.3 105 ) b. 0.100 M sodium propanoa

Allisa [31]

Answer:

a) pH = 2.95

b) pH = 8.94

c) pH = 7.00

d) pH = 4.89

Explanation:

a) The reaction is:

CH₃CH₂COOH(aq) + H₂O(l) ⇄ CH₃CH₂COO⁻(aq) + H₃O⁺(aq)(1)

At equlibrium: 0.1 - x x x

The dissociation constant of equation (1), Ka, is:

$K_{a} = \frac{[C_{3}H_{5}O_{2}^{-}][H_{3}O^{+}]}{[C_{3}H_{6}O_{2}]}$

$1.3\cdot 10^{-5} = \frac{x^{2}}{(0.1 - x)}$ (2)

Solving equation (2) for x, we have:

x = 0.00113 = [H₃O⁺] = [CH₃CH₂COO⁻]

Hence, the pH is:

$pH = -log [H_{3}O^{+}] = -log (0.00113) = 2.95$

b) The reaction is:

CH₃CH₂COO⁻(aq) + H₂O(l) ⇄ CH₃CH₂COOH(aq) + OH⁻(aq)

At equlibrium: 0.1 - x x x

The dissociation constant of the above equation, Kb, is:

$K_{b} = \frac{[C_{3}H_{6}O_{2}][OH^{-}]}{[C_{3}H_{5}O_{2}^{-}]}$

Also, we have that:

$K_{w} = K_{a}*K_{b} \rightarrow K_{b} = \frac{K_{w}}{K_{a}} = \frac{1 \cdot 10^{-14}}{1.3 \cdot 10^{-5}} = 7.69 \cdot 10^{-10}$

$7.69\cdot 10^{-10} = \frac{x^{2}}{0.1 - x}$ (3)

Solving equation (3) for x, we have:

x = 8.77x10⁻⁶ = [OH⁻] = [CH₃CH₂COOH]

Hence, the pH is:

$pOH = -log[OH^{-}] = -log(8.77\cdot 10^{-6}) = 5.06 \rightarrow pH = 14 - pOH = 8.94$

c) Pure water:

H₂O ⇄ H⁺ + OH⁻

$K_{w} = [H^{+}][OH^{-}] \rightarrow 1\cdot 10^{-14} = [H^{+}][OH^{-}]$

Since is pure water: [H⁺] = [OH⁻]

$1\cdot 10^{-14} = [H^{+}]^{2} \rightarrow [H^{+}] = \sqrt{1\cdot 10^{-14}} = 1 \cdot 10^{-7}$

Therefore, the pH is:

$pH = -log [H^{+}] = -log (1 \cdot 10^{-7}) = 7.00$

d) The reaction is:

CH₃CH₂COOH(aq) + H₂O(l) ⇄ CH₃CH₂COO⁻(aq) + H₃O⁺(aq)

At equlibrium: 0.1 0.1 x

The pH is:

$pH = pKa + log(\frac{[C_{3}H_{5}O_{2}^{-}]}{[C_{3}H_{6}O_{2}]}) = -log(1.3 \cdot 10^{-5}) + log(\frac{0.1}{0.1}) = 4.89$

I hope it helps you!

4 0

3 years ago

How sedimentary rock is formed

Shkiper50 [21]

Sedimentary rocks are formed from deposits of pre-existing rocks or pieces of once-living organism that accumulate on the Earth's surface. If sediment is buried deeply, it becomes compacted and cemented, forming sedimentary rock

hope this helps

8 0

2 years ago

Read 2 more answers

The amount of space an object takes up is called _____. gravity weight mass volume

baherus [9]

Volume is the amount of space an object takes up

4 0

3 years ago

As with any drug, aspirin (acetylsalicylic acid) must remain in the bloodstream long enough to be effective. Assume that the rem

Olenka [21]

Answer:

180 mg

Explanation:

For a first-order reaction, we can calculate the amount of aspirine (A) at a certain time (t) using the following expression.

$A=A_{0}.e^{-k.t}$

where,

k: rate constant

A₀: initial amount

If we know the half-life ( $t_{1/2}$ ) we can calculate the rate constant.

$k=\frac{ln2}{t_{1/2}} =\frac{ln2}{3h} =0.2h^{-1}$

When t = 4 h and A₀ = 400 mg, A is:

$A=400mg.e^{-0.2h^{-1}\times 4h} =180mg$

4 0

3 years ago

What is the difference between food web and food chain and what do they have in common?

abruzzese [7]

A food web is a system of interlocking and interdependent food chains.

A food chain is a hierarchical series of organisms each dependent on the next as a source of food.

Basically, the difference of the two is that a food web contains multiple different species in the same level that eat the animal below it's status. A food chain is one after the other.

7 0

3 years ago