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4 years ago

Compare and contrast chemical change and physical change

1 answer:

3 0

Well physical would be if you have Clay and you molded into a new shape or if you put butter on your toes and it melts or water evaporating from the surface of the ocean chemical changes would be milk going sour jewellery tarnishing which means turning into a different color or rust bread putting it in the oven and turning it into toes or rust forming on the nail that is left outside

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If the pKa value for a given acid is low, what does that say about the acid (is it weak or strong)?

Dmitry [639]

Answer:

If the pKa of the acid is low (negative), then the acid is strong.

Explanation:

Ka, <em>the acid ionization constant, </em>measures the strength of an acid in a solution. Stronger acids have higher Ka values.

We defined: pKa = -log[Ka]

This function is a decreasing function, meaning that pKa will be getting smaller and smaller, while increasing Ka (high values of Ka will have negative pKa values). Therefore, stronger acids (high values of Ka), will have low (negative) pKa values.

3 0

3 years ago

Will a precipitate form from Pb(NO3)2(aq) and HCl(aq)?

Rus_ich [418]

1. Write out the formula Pb(NO3)2 (aq) + 2HCl (aq) ----> PbCl2 + 2HNO3 2. Use solubility guidelines (gotta memorize 'em) for the products to see if a solid forms Nitrates are always soluble so 2HNO3 (aq) Chlorides (Cl) are always soluble except for when you mix them with copper, lead, mercury, or silver. Since you mixed it with lead (Pb) it is solid and forms a precipitate. PbCl2 (s)

5 0

3 years ago

I have 2 samples of solid chalk (aka calcium carbonate). Sample A has a total mass of 4.12 g and Sample B has a total mass of 19

IRINA_888 [86]

Answer:

A) Sample B has more calcium carbonate molecules

Explanation:

M = Molar mass of calcium carbonate = 100.0869 g/mol

$N_A$ = Avogadro's number = $6.022\times 10^{23}\ \text{mol}^{-1}$

For the 4.12 g sample

Moles of a substance is given by

$n=\dfrac{m}{M}\\\Rightarrow n=\dfrac{4.12}{100.0869}\\\Rightarrow n=0.0411\ \text{mol}$

Number of molecules is given by

$nN_A=0.0411\times 6.022\times 10^{23}=2.48\times 10^{22}\ \text{molecules}$

For the 19.37 g sample

$n=\dfrac{19.37}{100.0869}\\\Rightarrow n=0.193\ \text{mol}$

Number of molecules is given by

$nN_A=0.193\times 6.022\times 10^{23}=1.16\times 10^{23}\ \text{molecules}$

$1.16\times 10^{23}\ \text{molecules}>2.48\times 10^{22}\ \text{molecules}$

So, sample B has more calcium carbonate molecules.

The ratio of the elements of carbon, oxygen, calcium atoms, ions, has to be same in both the samples otherwise the samples cannot be considered as calcium carbonate. Same is applicable for impurities. If there are impurites then the sample cannot be considered as calcium carbonate.

7 0

3 years ago

Are your knees the elbows of your legs or are your elbows the knees of your

Nimfa-mama [501]

Answer:

Explanation:

it is confusing lol

but i think that it is C.both

hope it helps

have a nice day

5 0

3 years ago

Read 2 more answers

Term that means to break down

astraxan [27]

Answer:

decompose

Explanation:

3 0

4 years ago