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4 years ago

What is a prediction?

2 answers:

8 0

A prediction is not based upon evidence or reliable tests. A prediction is a guess as to what will happen in the future. Forecasts for example are nothing more than prediction, as even with "meteorological evidence", nothing is ever truly sure when in regard to wheather.

So "A"

lesya692 [45]4 years ago

5 0

A conclusion derived from evidence and logical reasoning

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Consider a mixture of NaCl and NaNO3 that is 31.8% Na by mass. Calculate the percentage by mass of NaCl in the mixture.

lutik1710 [3]

Answer: The percentage by mass of NaCl in the mixture is 38.5 %

Explanation:

To calculate the mass percentage of element in compound, we use the equation:

$\text{Mass percent of element}=\frac{\text{Mass of element}}{\text{Mass of compound}}\times 100$ .......(1)

For NaCl:

Mass of sodium element = 23 g

Mass of NaCl = 58.5 g

Putting values in equation 1, we get:

$\text{Mass percent of sodium element}=\frac{23g}{58.5g}\times 100=39.32\%$

Mass fraction of sodium metal in NaCl = 0.3932

For $NaNO_3$ :

Mass of sodium element = 23 g

Mass of $NaNO_3$ = 85 g

Putting values in equation 1, we get:

$\text{Mass percent of sodium element}=\frac{23g}{85g}\times 100=27.1\%$

Mass fraction of sodium metal in sodium nitrate = 0.271

Let us assume the mass fraction of NaCl in the mixture is 'x'

So, the mass fraction of $NaNO_3$ in the mixture will be '(1-x)'

We are given:

Percent by mass of Na in the mixture = 31.8 %

Mass fraction of Na in the mixture = 0.318

Evaluating the mass fraction of NaCl in the mixture:

$[(x\times 0.3932)+((1-x)\times 0.271)]=0.318$

x = 0.385

Percent by mass of NaCl in the mixture will be = $(0.385\times 100)=38.5\%$

Hence, the percentage by mass of NaCl in the mixture is 38.5 %

4 0

3 years ago

Which one of the following reactions would produce t-butyl methyl ether in high yield?

swat32

Answer:

D) sodium t-butoxide + bromomethane

Explanation:

The alkoxide ion is a strong nucleophile, that unlike alcohols, will react with primary alkyl halides to form ether. This general reaction is known as the Williamson synthesis, and is a SN₂ displacement. The alkyl halide must be primary so the back side attack is not hindered, and the alkoxide ion must be formed with the most hindered group.

The mechanism can be seen in the attachment.

7 0

4 years ago

Answer truthfully:))

BartSMP [9]

Answer:

b) velocity.

c) velocity, m/s²

d)change in velocity, change in direction, change in both velocity and direction.

e) increasing or decreasing

3 0

3 years ago

Help me please and only answer if you know what the answer is

avanturin [10]

They have similar chromosomes

3 0

3 years ago

What mass (g) of potassium chloride is contained in 430.0 mL of a potassium chloride solution that has a chloride ion concentrat

fredd [130]

Answer:

6.178 g.

Explanation:

KCl is ionized in the solution as:

KCl → K⁺ + Cl⁻.

∴ [KCl] = [K⁺] = [Cl⁻] = 0.193 M.

Molarity is defined as the no. of moles of the solute per 1.0 L of the solution.

∵ M = [(mass/molar mass)KCl][(1000)/(V of the solution)].

∴ mass of KCl = (M)(molar mass of KCl)(V of the solution)/1000 = (0.193 M)(74.55 g/mol)(430.0 mL)/1000 = 6.178 g.

8 0

3 years ago