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3 years ago

Why is calcium in group 2A if the modern periodic table

1 answer:

4 0

Calcium is in group 2A because it has two valence electrons and an oxidation state of 2+. Hope this is accurate & helpful! Enjoy your evening.

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It is necessary to make 225 mL of 0.222 M solution of nitric acid. Looking on the shelf, you see only 16 M nitric acid. How much

nalin [4]

Explanation:

The required concentration of $HNO_3$ M1 =0.222 M.

The required volume of $HNO_3$ is V1 =225 mL.

The standard solution of $HNO_3$ is M2 =16 M.

The volume of standard solution required can be calculated as shown below:

Since the number of moles of solute does not change on dilution.

The number of moles $n=molarity * volume$

$M_1.V_1=M_2.V_2$

$V2=\frac{M_1.V_1}{M_2} \\=0.222M x 225 mL / 16 M\\=3.12 mL$

Hence, 3.12 mL of 16 m nitric acid is required to prepare 0.222 M and 225 mL of nitric acid.

6 0

3 years ago

Chromium(III) oxide can be prepared by heating chromium(IV) oxide in vacuo at high temperature: 4Cr02 —2Cr2O3 +02 The reaction o

kkurt [141]

Answer: The theoretical yield and percent yield of chromium (III) oxide is 434.72 grams and 92.6 % respectively.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

Given mass of $CrO_2$ = 480.1 g

Molar mass of $CrO_2$ = 84 g/mol

Putting values in equation 1, we get:

$\text{Moles of }CrO_2=\frac{480.1g}{84g/mol}=5.72mol$

For the given chemical equation:

$4CrO_2\rightarrow 2Cr_2O_3+O_2$

By Stoichiometry of the reaction:

4 moles of $CrO_2$ produces 2 moles of chromium (III) oxide

So, 5.72 moles of $CrO_2$ will produce = $\frac{2}{4}\times 5.72=2.86mol$ of chromium (III) oxide

Now, calculating the mass of chromium (III) oxide from equation 1, we get:

Molar mass of chromium (III) oxide = 152 g/mol

Moles of chromium (III) oxide = 2.86 moles

Putting values in equation 1, we get:

$2.86mol=\frac{\text{Mass of chromium (III) oxide}}{152g/mol}\\\\\text{Mass of chromium (III) oxide}=(2.86mol\times 152g/mol)=434.72g$

To calculate the percentage yield of chromium (III) oxide, we use the equation:

$\%\text{ yield}=\frac{\text{Experimental yield}}{\text{Theoretical yield}}\times 100$

Experimental yield of chromium (III) oxide = 402.4 g

Theoretical yield of chromium (III) oxide = 434.72 g

Putting values in above equation, we get:

$\%\text{ yield of chromium (III) oxide}=\frac{402.4g}{434.72g}\times 100\\\\\% \text{yield of chromium (III) oxide}=\%$

Hence, the theoretical yield and percent yield of chromium (III) oxide is 434.72 grams and 92.6 % respectively.

7 0

3 years ago

The United States has about which percentage of the world's coal reserves?

aev [14]

Answer:

The United States leads the world with over 260 billion short tons of recoverable coal reserves—28% of total global reserves and 50% more than Russia, which possesses the world's second largest reserves. so the answer would be 28%

Explanation:

5 0

3 years ago

Read 2 more answers

A solution is made by dissolving 23.5 grams of glucose (C6H12O6) in 0.245 kilograms of water. If the molal freezing point consta

aalyn [17]

Answer:

- 0.99 °C ≅ - 1.0 °C.

Explanation:

We can solve this problem using the relation:

ΔTf = (Kf)(m),

where, ΔTf is the depression in the freezing point.

Kf is the molal freezing point depression constant of water = -1.86 °C/m,

m is the molality of the solution (m = moles of solute / kg of solvent = (23.5 g / 180.156 g/mol)/(0.245 kg) = 0.53 m.

∴ ΔTf = (Kf)(m) = (-1.86 °C/m)(0.53 m) = - 0.99 °C ≅ - 1.0 °C.

4 0

4 years ago

I need an answer now please asap and you will me marked brainiest please it's missing I need it now.

valentina_108 [34]

Answer:

C. NaHCO3 → Na2CO3 + H2O + CO2

Explanation:

» For a balanced equation, the number of atoms of reactants and products must be equal.

» In equation C, the reactant side has one sodium atom while ptoduct side has 2 sodium atoms.

» The balanced equations mus be;

${ \rm{ 2NaHCO _{3(aq)} → Na _{2}CO _{3(s)}+ H _{2} O _{(l)} + }CO _{2(g)} }$

7 0

2 years ago

Read 2 more answers