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3 years ago

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Chemistry

2 answers:

Ira Lisetskai [31]3 years ago

8 0

Answer:

true

Explanation:

cause im smart

enyata [817]3 years ago

6 0

Answer:

True, The Answer is true. Mechanical digestion involves physically breaking the food into smaller pieces.

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I NEED HELP FAST!!!!! Can you tell me about examples of elements compounds and mixtures??? I have a DBA in a few minutes and I d

Jet001 [13]

Okay Elements can combine to created element compounds a few examples can be lets say Gold(Au) Is an example of an Iconic Compound (usually a common compound). An Element Mixture is literal a mixture Ex. Brass. Brass is usually 10% copper and 45% zinc. So in order to get Brass you must physically m<span />ix copper with zinc and the other metal (sorry i don't remember the name) Also mixtures tend to not be chemically constant, this is because it was physically mixed rather than all of the atoms be the same if they were chemically combined.

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4 years ago

What is the ph of a 2.00 m hno2 solution if ka=5.00 e-6?

zysi [14]

Answer: -

2.5

Explanation: -

Initial [HNO₂] = 2.00 M

ka = 5.00 x 10 ⁻⁶

ICE table for HNO₂ =

[ $\left[\begin{array}{cccc}concentrations&HNO2&H+&NO2\\Initial&2.00&0&0\\Change&-x&+x&+x\\Equilibrium&2.00-x&x&x\end{array}\right]$

Ka = $\frac{x2}{2.00-x}$

5.00 x 10-6 = $\frac{x2}{2.00-x}$

x = 0.0032 M

pH = - log [H⁺]

= - log 0.0032

= 2.5

6 0

3 years ago

Carbon-14 has a half-life of 5,700 years.

Maksim231197 [3]

Answer:

$3.106\ \text{g}$

Explanation:

$t_{1/2}$ = Half-life of carbon = 5700 years

t = Time at which the remaining mass is to be found = 10400 years

$m_0$ = Initial mass of carbon = 11 g

Decay constant is given by

$\lambda=\dfrac{\ln2}{t_{1/2}}$

Amount of mass remaining is given by

$m=m_0e^{-\lambda t}\\\Rightarrow m=m_0e^{-\dfrac{\ln2}{t_{1/2}} t}\\\Rightarrow m=11e^{-\dfrac{\ln 2}{5700}\times 10400}\\\Rightarrow m=3.106\ \text{g}$

The amount of the substance that remains after 10400 years is $3.106\ \text{g}$ .

5 0

3 years ago

PLEASE ANSWER QUICKLY!! 25. Which gas sample contains a total of 3.0 x 1023 molecules?

nevsk [136]

Answer:

14 g of N2

Explanation:

If we look at the options, we will notice that the correct answer needs to be a gas that has about half of the molecular mass of the gas.

If we consider nitrogen gas whose molecular mass is 28g/mol, half of the molecular mass is 14 g.

So;

28g of N2 contains 6.02 × 10^23 molecules of N2

14g of N2 contains 14 × 6.02 × 10^23 /28

= 3.0 x 10^23

4 0

3 years ago

Cryolite, Na3AlF6(s), an ore used in the production of aluminum, can be synthesized using aluminum oxide. Balance the equation f

Korvikt [17]

Answer:

$55.2kgNa_{3}AlF_{6}$

Explanation:

1. First balance the equation for the synthesis of cryolite:

$Al_{2}O_{3}_{(s)}+6NaOH_{(l)}+12HF_{(g)}=2Na_{3}AlF_{6}+9H_{2}O_{(g)}$

2. Find the limiting reagent between the $Al_{2}O_{3},NaOH$ and $HF$

- First calculate the number of moles of each compound using its molar mass and the mass that reacted completely:

$13.4kgAl_{2}O_{3}*\frac{1molAl_{2}O_{3}}{101.96gAl_{2}O_{3}}*\frac{1000g}{1kg}=131molesAl_{2}O_{3}$

$55.4kgNaOH*\frac{1molNaOH}{40kgNaOH}*\frac{1000g}{1kg}=1385molesNaOH$ $55.4kgHF*\frac{1molHF}{20kgHF}*\frac{1000g}{1kg}=2770molesHF$

- Divide the number of moles obtained between the stoichiometric coefficient of each compound in the chemical reaction:

$Al_{2}O_{3}:\frac{131}{1}=131$

$NaOH:\frac{1385}{6}=231$

$HF:\frac{2770}{12}=231$

The $Al_{2}O_{3}$ is the limiting reagent because it has the smallest number.

3. Find the mass of cryolite produced:

$13.4kgAl_{2}O_{3}*\frac{1molAl_{2}O_{3}}{0.10196kgAl_{2}O_{3}}*\frac{2molesNa_{3}AlF_{6}}{1molAl_{2}O_{3}}*\frac{0.20994kgNa_{3}AlF_{6}}{1molNa_{3}AlF_{6}}=55.2kgNa_{3}AlF_{6}$

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4 years ago