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xxTIMURxx [149]
3 years ago
6

How many copper atoms are in a pure copper statue with a mass of 142kg

Chemistry
1 answer:
Ksenya-84 [330]3 years ago
5 0
142 kg in grams:

1 kg ---------- 1000 g
142 kg -------- ?

142 x 1000 / 1 => 142000 g 

Atomic mass Cu =  63.54 a.m.u

Therefore:

63.54 g ------------ 6.02x10²³ atoms
142000 g --------- ??

142000 x ( 6.02x10²³) / 63.54 =

8.54.10²⁸ / 63.54 => 1.34.10²⁷ atoms of Cu



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Labels of many food products have expiration dates, at which point they are typically removed from the supermarket shelves. A pa
White raven [17]

Answer:

Explanation:

Since it first order, we use order rate equation

In ( \frac{A1}{A0}) = -kt where A1 is the final quality = 0.8 (80%), A0 is the initial quality = 1 ( 100%)

also, t half life = \frac{In2}{k} where k is rate constant

k = \frac{In 2}{45 days} = 0.0154

In ( \frac{0.8}{1}) = - 0.0154 t

-0.223 / -0.0154 = t

t = 14.49 approx 14.5 days from the date the yogurt was packaged

6 0
4 years ago
Density of a piece of wood that has a measurement of 24 cm3 and 768 g
Brut [27]

Answer:

<h3>The answer is 32 g/cm³</h3>

Explanation:

The density of a substance can be found by using the formula

density =  \frac{mass}{volume} \\

From the question

mass = 768 g

volume = 24 cm³

We have

density =  \frac{768}{24}  \\

We have the final answer as

<h3>32 g/cm³</h3>

Hope this helps you

4 0
3 years ago
Read 2 more answers
Consider the following reaction between mercury(II) chloride and oxalate ion:
siniylev [52]

Answer : The reaction rate will be, 1.9\times 10^{-4}M/s

Explanation :

Rate law is defined as the expression which expresses the rate of the reaction in terms of molar concentration of the reactants with each term raised to the power their stoichiometric coefficient of that reactant in the balanced chemical equation.

For the given chemical equation:

2HgCl_2(aq)+C_2O_2^{4-}(aq)\rightarrow 2Cl^-(aq)+2CO_2(g)+HgCl_2(s)

Rate law expression for the reaction:

\text{Rate}=k[HgCl_2]^a[C_2O_2^{4-}]^b

where,

a = order with respect to HgCl_2

b = order with respect to C_2O_2^{4-}

Expression for rate law for first observation:

3.2\times 10^{-5}=k(0.164)^a(0.15)^b ....(1)

Expression for rate law for second observation:

2.9\times 10^{-4}=k(0.164)^a(0.45)^b ....(2)

Expression for rate law for third observation:

1.4\times 10^{-4}=k(0.082)^a(0.45)^b ....(3)

Expression for rate law for fourth observation:

4.8\times 10^{-5}=k(0.246)^a(0.15)^b ....(4)

Dividing 1 from 2, we get:

\frac{2.9\times 10^{-4}}{3.2\times 10^{-5}}=\frac{k(0.164)^a(0.45)^b}{k(0.164)^a(0.15)^b}\\\\9=3^b\\(3)^2=3^b\\b=2

Dividing 3 from 2, we get:

\frac{2.9\times 10^{-4}}{1.4\times 10^{-4}}=\frac{k(0.164)^a(0.45)^b}{k(0.082)^a(0.45)^b}\\\\2=2^a\\a=1

Thus, the rate law becomes:

\text{Rate}=k[HgCl_2]^1[C_2O_2^{4-}]^2

Now, calculating the value of 'k' by using any expression.

Putting values in above rate law, we get:

3.2\times 10^{-5}=k(0.164)^1(0.15)^2

k=8.7\times 10^{-3}M^{-2}s^{-1}

Now we have to determine the reaction rate when the concentration of HgCl_2 is 0.135 M and that of C_2O_2^{-4} is 0.40 M.

\text{Rate}=k[HgCl_2]^1[C_2O_2^{4-}]^2

\text{Rate}=(8.7\times 10^{-3})\times (0.135)^1\times (0.40)^2

\text{Rate}=1.9\times 10^{-4}M/s

Therefore, the reaction rate will be, 1.9\times 10^{-4}M/s

6 0
4 years ago
If 31.6 g of KMnO4 is dissolved in enough water to give 160 mL of solution, what is the molarity?
Zina [86]

Answer:

A. 1.25M

B. 19.98g

Explanation:

A. Data obtained from the question include the following:

Mass of KMnO4 = 31.6 g

Volume = 160 mL

Molarity =..?

We'll begin by calculating the number of mole KMnO4 in the solution. This is can be obtained as follow:

Mass of KMnO4 = 31.6 g

Molar mass of KMnO4 = 39 + 55 + (16x4) = 158g/mol

Number of mole of KMnO4 =..?

Mole = mass /Molar mass

Number of mole of KMnO4 = 31.6/158 = 0.2 mole

Now, we can obtain the molarity of the solution as follow:

Volume = 160 mL = 160/1000 = 0.16L

Mole of KMnO4 = 0.2 mole

Molarity = mole /Volume

Molarity = 0.2/0.16 = 1.25M

B. Data obtained from the question include the following:

Volume = 300mL

Molarity = 0.74 M

Mass of H2C2O4 =..?

First, we shall determine the number of mole H2C2O4. This is illustrated below:

Volume = 300mL = 300/1000 = 0.3L

Molarity = 0.74 M

Mole of H2C2O4 =?

Mole = Molarity x Volume

Mole of H2C2O4 = 0.74 x 0.3

Mole of H2C2O4 = 0.222 mole

Now, we can easily find the mass of H2C2O4 by converting 0.222 mole to grams as shown below:

Number of mole of H2C2O4 = 0.222 mole

Molar mass of H2C2O4 = (2x1) + (12x2) + (16x4) = 2 + 24 + 64 = 90g/mol

Mass of H2C2O4 =..?

Mass = mole x molar mass

Mass of H2C2O4 = 0.222 x 90

Mass of H2C2O4 = 19.98g

5 0
3 years ago
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