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4 years ago

Student mixes 5 g of sand into a beaker of 20 g of water. Is this a physical or chemical change-why?

Chemistry

1 answer:

oee [108]4 years ago

8 0

Physical change. the sand is not dissolving into the water, but simply finding a place in it.

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A mixture of hydrochloric and sulfuric acids is prepared so that it contains 0.315 M HCl and 0.125 M H2SO4. What volume of 0.55

Xelga [282]

Answer: The volume of NaOH required is 402.9 mL

Explanation:

To calculate the number of moles for given molarity, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}$ .....(1)

For HCl:

Molarity of HCl solution = 0.315 M

Volume of solution = 503.4 mL = 0.5034 L (Conversion factor: 1 L = 1000 mL)

Putting values in equation 1, we get:

$0.315M=\frac{\text{Moles of HCl}}{0.5034L}\\\\\text{Moles of HCl}=(0.315mol/L\times 0.5034L)=0.1586mol$

For sulfuric acid:

Molarity of sulfuric acid solution = 0.125 M

Volume of solution = 503.4 mL = 0.5034 L

Putting values in equation 1, we get:

$0.125M=\frac{\text{Moles of }H_2SO_4}{0.5034L}\\\\\text{Moles of }H_2SO_4=(0.125mol/L\times 0.5034L)=0.0630mol$

As, all of the acid is neutralized, so moles of NaOH = [0.1586 + 0.0630] moles = 0.2216 moles

Molarity of NaOH solution = 0.55 M

Moles of NaOH = 0.2216 moles

Putting values in equation 1, we get:

$0.55M=\frac{0.2216}{\text{Volume of solution}}\\\\\text{Volume of solution}=\frac{0.2216}{0.55}=0.4029L=402.9mL$

Hence, the volume of NaOH required is 402.9 mL

6 0

3 years ago

Name this chemical reaction H2 + 2 AgNO3 → 2 Ag + 2 HNO3

gulaghasi [49]

Answer:

Single Replacement Reaction

Explanation:

simply because only 1 element switched places.

6 0

3 years ago

Determine the percent ionization of a 0.225 M solution of benzoic acid. Express your answer using two significant figures.

Assoli18 [71]

Answer:

1.68% is ionized

Explanation:

The Ka of benzoic acid, C₇H₆O₂, is 6.46x10⁻⁵, the equilibrium in water of this acid is:

C₇H₆O₂(aq) + H₂O(l) ⇄ C₇H₅O₂⁻(aq) + H₃O⁺(aq)

Ka = 6.46x10⁻⁵ = [C₇H₅O₂⁻] [H₃O⁺] / [C₇H₆O₂]

Where [] are concentrations in equilibrium

In equilibrium, some 0.225M of the acid will react producing both C₇H₅O₂⁻ and H₃O⁺, the equilibrium concentrations are:

[C₇H₆O₂] = 0.225-X

[C₇H₅O₂⁻] = X

[H₃O⁺] = X

Replacing:

6.46x10⁻⁵ = [X] [X] / [0.225-X]

1.4535x10⁻⁵ - 6.46x10⁻⁵X = X²

1.4535x10⁻⁵ - 6.46x10⁻⁵X - X² = 0

Solving for X:

X = -0.0038. False solution, there is no negative concentrations.

X = 0.00378M. Right solution.

That means percent ionization (100 times Amount of benzoic acid ionized over the initial concentration of the acid) is:

0.00378M / 0.225M * 100 =

<h3>1.68% is ionized</h3>

8 0

3 years ago

Which set of measurements correctly identifies the speed of an object?

In-s [12.5K]

Answer:

A. Distance = 18 m

time = 2 hr

speed = 9 m/hr

Explanation:

Speed is the same thing as velocity.

Velocity = distance/time

18m/2hr = 9m/hr

For choice B, the numbers are right, but the units are mixed (minutes were changed to hours)

4 0

3 years ago

What is the molarity of 3.0 L of solution containing 4.0 moles MgO

AysviL [449]

Explanation:

v=3.0L (to calculate M, volume must be in L)

n=4.0 moles

M=n/v (formula molarity)

=4.0/3.0

=1.333M

7 0

4 years ago