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3 years ago

I will give brainliest!! How long is the pencil? Make sure to use the appropriate amount of significant figures.

Chemistry

1 answer:

8090 [49]3 years ago

5 0

Answer: Option (c) is the correct answer.

Explanation:

The bottom of pencil is placed at the starting point of scale. Whereas the tip of pencil depicts the end point of its length.

The bottom of pencil is at 0 mm and tip of pencil is at 18.73 mm. The appropriate amount of significant figures is 18.73 mm.

Therefore, we can conclude that out of the given options, pencil is 18.73 mm long.

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3 years ago

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2 years ago

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"An aqueous CaCl2 solution has a vapor pressure of 83.1mmHg at 50 ∘C. The vapor pressure of pure water at this temperature is 92

Lynna [10]

Answer : The the concentration of $CaCl_2$ in mass percent is, 41.18 %

Solution : Given,

Molar mass of water = 18 g/mole

Molar mass of $CaCl_2$ = 110.98 g/mole

First we have to calculate the mole fraction of solute.

According to the relative lowering of vapor pressure, the vapor pressure of a component at a given temperature is equal to the mole fraction of that component of the solution multiplied by the vapor pressure of that component in the pure state.

$\fac{p^o-p_s}{p^o}=X_B$

where,

$p^o$ = vapor pressure of the pure component (water) = 92.6 mmHg

$p_s$ = vapor pressure of the solution = 83.1 mmHg

$X_B$ = mole fraction of solute, $(CaCl_2)$

Now put all the given values in this formula, we get the mole fraction of solute.

$\fac{92.6-83.1}{92.6}=X_B$

$X_B=0.102$

Now we have to calculate the mole fraction of solvent (water).

As we know that,

$X_A+X_B=1\\\\X_A=1-X_B\\\\X_A=1-0.102\\\\X_A=0.898$

The number of moles of solute and solvent will be, 0.102 and 0.898 moles respectively.

Now we have to calculate the mass of solute, $(CaCl_2)$ and solvent, $(H_2O)$ .

$\text{Mass of }CaCl_2=\text{Moles of }CaCl_2\times \text{Molar mass of }CaCl_2$

$\text{Mass of }CaCl_2=(0.102mole)\times (110.98g/mole)=11.32g$

$\text{Mass of }H_2O=\text{Moles of }H_2O\times \text{Molar mass of }H_2O$

$\text{Mass of }H_2O=(0.898mole)\times (18g/mole)=16.164g$

Mass of solution = Mass of solute + Mass of solvent

Mass of solution = 11.32 + 16.164 = 27.484 g

Now we have to calculate the mass percent of $CaCl_2$

$Mass\%=\frac{\text{Mass of}CaCl_2}{\text{Mass of solution}}\times 100=\frac{11.32g}{27.484g}\times 100=41.18\%$

Therefore, the the concentration of $CaCl_2$ in mass percent is, 41.18 %

4 0

2 years ago

Which of the following salts will be less soluble in 0.10 M NaCl than it is in pure water?

MariettaO [177]

The less soluble salt : PbCl₂

<h3>Further explanation</h3>

Given

0.1 M NaCl

Required

The less soluble salt

Solution

If we see from the answer option, the salt that is more difficult to dissolve in NaCl is PbCl₂ because it has the same ion (Cl)

When PbCl₂ is dissolved in water, ionization will occur

PbCl₂ ⇒ Pb²⁺+ 2Cl⁻

So, when dissolved in NaCl, NaCl itself will be ionized

NaCl ⇒ Na⁺ + Cl⁻

Based on the principle of equilibrium, the addition of an ion (one of the ions is enlarged), the reaction will shift towards the ion that was not added. In addition to this Cl ion, the reaction will shift to the left so that the solubility of PbCl₂ will decrease (the reaction to the right decreases)

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3 years ago