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anygoal [31]
3 years ago
10

A 29.2 mL sample of a 0.458 M aqueous hydrofluoric acid solution is titrated with a 0.337 M aqueous sodium hydroxide solution. W

hat is the pH at the start of the titration, before any sodium hydroxide has been added
Chemistry
1 answer:
Svetach [21]3 years ago
4 0

Answer:

3.51

Explanation:

Before any sodium hydroxide has been added, the pH is that of the aqueous hydrofluoric acid solution.

HF is a weak acid that dissociates according to the following equation.

HF(aq) ⇄ H⁺(aq) + F⁻(aq)      Ka = 6.76 × 10⁻⁴

We can find [H⁺] using the following expression.

[H⁺] = √(Ca × Ka)

where

Ca: concentration of the acid

Ka: acid dissociation constant

[H⁺] = √(Ca × Ka)

[H⁺] = √(0.458 × 6.76 × 10⁻⁴)

[H⁺] = 3.10 × 10⁻⁴ M

The pH is:

pH = -log [H⁺]

pH = -log 3.10 × 10⁻⁴ = 3.51

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Calculate: (a) the weight (in lbf) of a 30.0 lbm object. (b) the mass in kg of an object that weighs 44N. (c) the weight in dyne
belka [17]

Answer:

a) 965,1 lbf

b) 4,5 kg

c) 1,33 * 10^6 dynes

Explanation:

Mass of an object refers to the amount of mattter it cotains, it can be expressed it gr, kg, lbm, ton, etc.

Weight of an object refers to a force, and is the measurement of the pull of gravitiy on an object. It may be definide as the mass times the acceleration of gravity.

                                        w=mg

In Planet Earth, the nominal "average" value for gravity is 9,8 m/s² (in the International  System) or 32,17 ft/s² (in the FPS system).

To solve this problem we'll use the following conversion factors:

1 lbf = 1 lbm*ft/s²

1 N = 1 kg*m/s²

1 dyne = 1 gr*cm/s²   and 1 N =10^5 dynes

1 ton = 907,18 kg

1 k = 1000 gr

a) m = 30 lbm

w = 30 lbm * 32,17 ft/s^{2} = 965, 1 \frac{lmb*ft}{s^{2} } = 965,1 lbf

b) w = 44 N

First, we clear m of the weight equation and then we replace our data.

m = \frac{w}{g} = \frac{44 N}{9,8 \frac{m}{{s}^{2}} } = 4,5 kg

c) m = 15 ton

m=15 ton * \frac{907,18 kg}{1 ton} = 13607,7 kg \\ w = mg = 13607,7 kg * 9,8 m/s2 = 133355,5 N * \frac{10^{5} dynes }{1 N} = 1,33 * 10^{6}dynes

4 0
4 years ago
Which group on the periodic table already stable?
viktelen [127]
The noble gases AKA the column with full outermost valence shells. (Group 18)
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The atmospheric pressure on the surface of Venus is 6.84X10^4. Calculate the atmospheric pressure in atm and torr. Round each of
quester [9]

Answer:

0.675 atm

513 Torr

Explanation:

Given is that, the atmospheric pressure on the surface of Venus is

6.84 X 10⁴ Pa.

1 atm (atmospheric pressure) is equal to 101325 pascal (Pa).

To convert divide the pressure value by 101325.

Pressure in atm = \frac{6.84 \times 10^{4} }{101325}

= 0.675055 atm

Rounding it off to 3 significant digits: 0.675 atm

Now,  one Torr is 133.322 Pa. For conversion, divide the pressure value by 133.322.

Pressure in Torr = \frac{6.84 \times 10^{4} }{133.322}

=513.04219 Torr

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5 0
3 years ago
The heat of vaporization of water at 100°c is 40.66 kj/mol. Calculate the quantity of heat that is absorbed/released when 9.00 g
timofeeve [1]

Answer:

20.3 kJ of heat is absorbed when 9.00 g of steam condenses to liquid water.

Explanation:

Heat is being consumed during vaporization and heat is being released during condensation.

To vaporize 1 mol of water, 40.66 kJ of heat is being consumed.

Molar mass of water = 18.02 g/mol

Hence, to vaporize 18.02 g of water , 40.66 kJ of heat is being consumed.

So, to vaporize 9.00 g of water, (\frac{40.66}{18.02}\times 9.00)kJ of heat or 20.3 kJ of heat is being consumed

As condensation is a reverse process of vaporization therefore 20.3 kJ of heat is absorbed when 9.00 g of steam condenses to liquid water.

5 0
4 years ago
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