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3 years ago

Explain how to use a graph to show whether or not the speed of an object is constant.

Chemistry

1 answer:

Sonbull [250]3 years ago

3 0

Answer:

A horizontal line on a speed-time graph represents a constant speed. A sloping line on a speed-time graph represents an acceleration. The sloping line shows that the speed of the object is changing. The object is either speeding up or slowing down.

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The gas in the piston is at constant temperature. A student increases the pressure on the piston from 2 atm to 3 atm. The observ

Vesna [10]

Answer: row 1, the volume decreases when the pressure increased

Explanation:

7 0

3 years ago

"How much NH4Cl, when present in 2.00 liters of 0.200 M ammonia, will give a solution with pH = 8.20? For NH3, Kb = 1.8 x 10-5"

Andru [333]

Answer:

245.66g of NH₄Cl is the mass we need to add to obtain the desire pH

Explanation:

The mixture of NH3/NH4Cl produce a buffer. We can find the pH of a buffer using H-H equation:

pH = pKa + log [A⁻] / [HA]

Where [A⁻] is the molar concentration of the base, NH₃, and [HA] molar concentration of the acid, NH₄⁺. This molar concentration can be taken as the moles of each chemical

First, we need to find pKa of NH₃ using Kb. Then, the moles of NH₃ and finally replace these values in H-H equation to solve moles of NH₄Cl we need to obtain the desire pH.

pKa NH₃/NH₄⁺

pKb = - log Kb

pKb = -log 1.8x10⁻⁵ = 4.74

pKa = 14 - pKb

pKa = 14 - 4.74

pKa = 9.26

Moles NH₃

2.00L ₓ (0.200mol NH₃ / L) = 0.400 moles NH₃

H-H equation:

pH = pKa + log [NH₃] / [NH₄Cl]

8.20 = 9.26 + log [0.400 moles] / [NH₄Cl]

-1.06 = log [0.400 moles] / [NH₄Cl]

0.0087 = [0.400 moles] / [NH₄Cl]

[NH₄Cl] = 0.400 moles / 0.0087

[NH₄Cl] = 4.59 moles of NH₄Cl we need to add to original solution to obtain a pH of 8.20. In grams (Using molar mass NH₄Cl=53.491g/mol):

4.59 moles NH₄Cl ₓ (53.491g / mol) =

<h3>245.66g of NH₄Cl is the mass we need to add to obtain the desire pH</h3>

3 0

4 years ago

How many half-lives are required for the concentration of reactant to decrease to 1.56% of its original value?4247.56.56

neonofarm [45]

Answer:

6 half-lives are required for the concentration of reactant to decrease to 1.56% of its original value.

Explanation:

Using integrated rate law for first order kinetics as:

$[A_t]=[A_0]e^{-kt}$

Where,

$[A_t]$ is the concentration at time t

$[A_0]$ is the initial concentration

Given:

Concentration is decreased to 1.56 % which means that 0.0156 of $[A_0]$ is decomposed. So,

$\frac {[A_t]}{[A_0]}$ = 0.0156

Thus,

$\frac {[A_t]}{[A_0]}=e^{-k\times t}$

$0.0156=e^{-k\times t}$

kt = 4.1604

The expression for the half life is:-

Half life = 15.0 hours

$t_{1/2}=\frac {ln\ 2}{k}$

Where, k is rate constant

So,

$k=\frac {ln\ 2}{t_{1/2}}$

$\frac{4.1604}{t}=\frac {ln\ 2}{t_{1/2}}$

$t = 6\times t_{1/2}$

6 half-lives are required for the concentration of reactant to decrease to 1.56% of its original value.

6 0

3 years ago

The flame in a torch used to cut metal is produced by burning acetylene (C2H2) in pure oxygen. Assuming the combustion of 1 mole

Nookie1986 [14]

Answer:

19.8 kg of C₂H₂ is needed

Explanation:

We solve this by a rule of three:

If 1251 kJ of heat are relased in the combustion of 1 mol of acetylene

95.5×10⁴ kJ of heat may be released by the combustion of

(95.5×10⁴ kJ . 1) /1251kJ = 763.4 moles of C₂H₂

Let's convert the moles to mass → 763.4 mol . 26 g/1 mol = 19848 g

If we convert the mass from g to kg → 19848 g . 1kg / 1000g = 19.8 kg

7 0

3 years ago

Read 2 more answers

1. A solution with a pH of 9 has a pOH of

Alecsey [184]

Answer:

strength = 10⁻²/10⁻³ = 10 times more acidic

Explanation:

1. A solution with a pH of 9 has a pOH of

pH + pOH = 14 => pOH = 14 - pH = 14 - 9 = 5

2. Which is more acidic, a solution with a pH of 6 or a pH of 4?

pH of 4 => Higher [H⁺] = 10⁻⁴M vs pH of 6 => [H⁺] = 10⁻⁶M

3. How many times more acidic is a solution with a pH of 2 than a solution with a pH of 3?

soln with pH = 2 => [H⁺] = 10⁻²M

soln with pH = 3 => [H⁺] = 10⁻³M

strength = 10⁻²/10⁻³ = 10 times more acidic

4. What is the hydrogen ion concentration [H + ] in a solution that has a pH of 8?

[H⁺] = 10^-pH = 10⁻⁸M

5. A solution has a pOH of 9.6. What is the pH? (Use the formula.)

pH + pOH = 14 => pH = 14 - 9.6 = 4.4

8 0

3 years ago