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3 years ago

How many grams of NaOH are needed to make 500 mL of a 2.5 M NaOH solution

1 answer:

4 0

The number of grams of NaOH that are needed to make 500 ml of 2.5 M NaOH solution

calculate the number of moles =molarity x volume/1000

= 2.5 x 500/1000 = 1.25 moles

mass = moles x molar mass of NaOH

= 1.25 x40= 50 grams of NaOH

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A sample of 28 Mg decays initially at a rate of 53500 disintegrations per minute, but the decay rate falls to 10980 disintegrati

prisoha [69]

Answer : The half life of 28-Mg in hours is, 6.94

Explanation :

First we have to calculate the rate constant.

Expression for rate law for first order kinetics is given by:

$k=\frac{2.303}{t}\log\frac{a}{a-x}$

where,

k = rate constant

t = time passed by the sample = 48.0 hr

a = initial amount of the reactant disintegrate = 53500

a - x = amount left after decay process disintegrate = 53500 - 10980 = 42520

Now put all the given values in above equation, we get

$k=\frac{2.303}{48.0}\log\frac{53500}{42520}$

$k=9.98\times 10^{-2}hr^{-1}$

Now we have to calculate the half-life.

$k=\frac{0.693}{t_{1/2}}$

$9.98\times 10^{-2}=\frac{0.693}{t_{1/2}}$

$t_{1/2}=6.94hr$

Therefore, the half life of 28-Mg in hours is, 6.94

8 0

3 years ago

Which best describes an element?

Aleonysh [2.5K]

I think the answer is a pure substance

6 0

3 years ago

<img src="https://tex.z-dn.net/?f=%7B%5Clarge%7B%5Cred%7B%5Cmapsto%7B%5Cmaltese%7B%5Cunderline%7B%5Cgreen%7B%5Cboxed%7B%5Cblue%7

RoseWind [281]

Answer:

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Raoult's law states that the vapor pressure of a solvent above a solution is equal to the vapor pressure of the pure solvent at the same temperature scaled by the mole fraction of the solvent present: Psolution=χsolventPosolvent.

5 0

3 years ago

How many pints are in a 48 cups?

Feliz [49]

1 cup = 2 pints

48 × 2 = 96 pints

HOPE THIS HELPED
:)

8 0

3 years ago

At a temperature of 273 K, a 400.-milliliter gas sample has a pressure of 760. millimeters of mercury. If the pressure is change

KatRina [158]

Answer:

188.03K

Explanation:

The following data were obtained from the question:

T1 (initial temperature) =273K

V1 (initial volume) = 400mL

P1 (initial pressure) = 760mmHg

P2 (final pressure) = 380mmHg

V2 (final volume) = 551mL

T2 (final temperature) =?

Applying the general gas equation P1V1/T1 = P2V2/T2, the final temperature of the gas can be obtained as follow:

P1V1/T1 = P2V2/T2

760 x 400/273 = 380 x 551/T2

Cross multiply to express in linear form as shown below:

760 x 400 x T2 = 273 x 380 x 551

Divide both side by 760 x 400

T2 = (273 x 380 x 551)/(760 x 400)

T2 = 188.03K.

Therefore, at a temperature of 188.03K, the gas sample will have a volume of 551mL

3 0

3 years ago