Why are burning candles and rusting nails examples of chemical change?

1 answer:

8 0

First Rusting is slow oxidation of iron into iron oxide using H2O and oxygen in atmosphere which is a chemical reaction.

burning is also a oxidation but kinda fast using oxygen in atmosphere to oxidize the hydrocarbon(paraffin wax) in candle to give heat and CO2.

So they are both chemical reactions which happens at different rate.

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Which statement is true about a polyatomic ion?

nataly862011 [7]

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A student obtains a 10.0g sample of a white powder labeled as BaCl2. After completely dissolving the powder in 50.0mL of distill

LekaFEV [45]

Answer:

Whether barium chloride solution was pure

Explanation:

We may answer whether barium chloride was pure. The sequence of this experiment might be depicted by the following balanced chemical equations:

$BaCl_2 (aq)\rightarrow Ba^{2+} (aq) + 2 Cl^- (aq)$

$Ba^{2+} (aq) + SO_4^{2-} (aq)\rightarrow BaSO_4 (s)$

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$\omega_{Ba^{2+}} = \frac{M_{Ba}}{M_{BaCl_2}} = \frac{137.327 g/mol}{208.23 g/mol\cdot 100\% = 65.95 \%$

This means in 10.0 g, we have a total of:

$m_{Ba^{2+}} = 10.0 g\cdot 0.6595 = 6.595 g$ of barium cations.

The precipitate is then formed and we measure its mass. Having its mass determined, we'll firstly find the percentage of barium in barium sulfate using the same approach:

$\omega_{Ba} = \frac{137.327 g/mol}{233.38 g/mol}\cdot 100\% = 58.84 \%$

Multiplying the mass we obtained by the fraction of barium will yield mass of barium in barium sulfate. Then:

if this number is equal to 6.595 g, we have a pure sample of barium chloride;
if this number is lower than 6.595 g, this means we have an impure sample of barium chloride, as we were only able to precipitate a fraction of 6.595 g.

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Answer:

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