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3 years ago

How many grams of solute are needed to make 37.5 mL of 0.750 M KI solution? Round to three significant digits.

Chemistry

1 answer:

Marysya12 [62]3 years ago

8 0

4.648 gm of solute is needed to make 37.5 mL of 0.750 M KI solution.

Solution:

We will start with the Molarity

$\text { Molarity }=\text { Mole of solute } \div \text { liter of solution }$

Also we know 1000 ml = 1 L

Therefore 37.5 ml by 1000ml we obtained 0.0375L

Equation for solving mole of solute

$\text { Mole of solute }=\text { Molarity } \times \text { Liters of solution }$

Now, multiply 0.750M by 0.0375

Substitute the known values in the above equation we get

$0.750 \times 0.0375=0.0281$

Also we know that Molar mass of KI is 166 g/mol

So divide the molar mass value to get the no of grams.

$0.028 \times 166=4.648$

So 4.648 gm of Solute is required for make 37.5 mL of 0.750 M KI solution.

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3 years ago

What is the binding energy of a nucleus that has a mass defect of 5.81*10-^29 kg

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Answer:

Choice A: Approximately $5.23 \times 10^{-29}$ joules.

Explanation:

Apply the famous mass-energy equivalence equation to find the energy that correspond to the $\rm 5.81\times 10^{-29}$ kilograms of mass.

$E = m \cdot c^{2}$ ,

where

$E$ stands for energy,
$m$ stands for mass, and
$c$ is the speed of light in vacuum.

The speed of light in vacuum is a constant. However, finding the right units for this value can simplify the calculations a lot. What should be the unit of $c$ ?

The mass given is in the appropriate SI unit:

Mass is in kilograms.

Thus, proceed with the speed of light in SI units. The SI unit for speed is meters per second. For the speed of light, $c \approx \rm 3.00\times 10^{8}\;m\cdot s^{-1}$ .

Apply the mass-energy equivalence:

$\begin{aligned} E &= m \cdot c^{2} \\ &= \rm 5.81\times 10^{-29}\; kg \times {\left(3.00\times 10^{8}\; m\cdot s^{-1}\right)}^{2}\\ &\approx \rm 5.23\times 10^{-12}\;kg\cdot m^{2}\cdot s^{-2} \end{aligned}$ .

The unit of energy is not in joules. Don't be alerted. Consider the definition of a joule of energy. One joule is the work done on an object when a force of one newton acts on the object in the direction of the force through the distance of one meter. (English Wikipedia.)

$\rm 1\; J = 1\; N \times 1\; m$ .

However, a force of one newton is defined as the force required to accelerated an object with a mass of one kilogram (not gram) at a rate of one meter per second squared. (English Wikipedia.)

$\begin{aligned}\rm 1\; J &= \rm 1\; N \times 1\; m\\ & = \rm \left(1\; kg\times 1\; m\cdot s^{-2}\right)\times 1\; m\\ &= \rm 1\; kg \cdot m^{2}\cdot s^{-2}\end{aligned}$ .