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3 years ago

What is the molarity of a solution of 17.0 g of nh4br in enough h2o to make 158 ml of solution? answer in units of m?

1 answer:

6 0

Unit of M is also mole/L, where mole is the moles of solute and L is the volume of the solution. The latter is given: 158 mL or 0.158 L. So we need to find out the moles of NH4Br.

Moles of NH4Br = Mass of NH4Br/molar mass of NH4Br = 17.0g/(14+1*4+79.9)g/mol = 0.1736 mole.

So, the molarity of the solution = 0.1736mole/0.158L = 1.10 mole/L = 1.10 M

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3 years ago

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How long, in seconds, would it take for the concentration of A to decrease from 0.860 M to 0.310 M?

kogti [31]

Answer:

2.038 seconds.

Explanation:

So, in the question above we are given the following parameters in order to solve this question. We are given a rate constant of 0.500 s^-, initial concentration= 0.860 M and final concentration= 0.310 M,the time,t =??.

Assuming that the equation for the first order of reaction is given below,that is;

A ---------------------------------> products.

Recall the formula below;

B= B° e^-kt.

Therefore, e^-kt = B/B°.

-kt = ln B/B°.

kt= ln B°/B.

Where B° and B are the amount of the initial concentration and the amount of the concentration remaining, k is the rate constant and t = time taken for the concentration to decrease.

So, we have; time taken,t = ln( 0.860/.310)/0.500.

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3 years ago

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4 years ago

A sample of fluorine contains isotopes with different masses; F-19 and F-18. In the sample 94% of the

zalisa [80]

The relative mass of the sample : 18.94

<h3>Further explanation </h3>

The elements in nature have several types of isotopes

Isotopes are atoms whose no-atom has the same number of protons while still having a different number of neutrons.

So Isotopes are elements that have the same Atomic Number (Proton)

Atomic mass is the average atomic mass of all its isotopes

Mass atom X = mass isotope 1 . % + mass isotope 2.%

F-19 = 94% of the sample

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The relative mass :

$\tt = 0.94\times 19+0.06\times 18\\\\=18.94$

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3 years ago

Hydrogen peroxide decomposes to form water and oxygen gas according to the following equation: 2H2O2(aq)  2H2O(l) + O2(g) If 31

olya-2409 [2.1K]

Answer:

141.89 dm^3

Explanation:

The equation of the reaction is;

2H2O2(aq) --------->2H2O(l) + O2(g)

Now , we are told that the mass of hydrogen peroxide decomposed was 315g. Number of moles of hydrogen peroxide in 315g of the substance is given by;

Number of moles= mass/molar mass

Molar mass of hydrogen peroxide= 34.0147 g/mol

Number of moles= 315g/34.0147 g/mol = 9.26 moles of hydrogen hydrogen peroxide.

From the reaction equation;

2 moles of hydrogen peroxide yields 1 mole of oxygen

9.26 moles of hydrogen peroxide yields 9.26 ×1/2 = 4.63 moles of oxygen

From the ideal gas equation;

Volume of the gas V= the unknown

Pressure of the gas P= 0.792 atm

Temperature of the gas= 23°C +273 = 296 K

Number of moles of oxygen = 4.63 moles of oxygen

R= 0.082atmdm^3K-1mol-1

Hence, from PV=nRT

V= nRT/P

V= 4.63 × 0.082 × 296/0.792 = 141.89 dm^3

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3 years ago