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Kazeer [188]
3 years ago
14

Explain why sharpening a pencil is different type of physical change than freezing water to make ice cubes

Chemistry
1 answer:
Ann [662]3 years ago
8 0
A pencil is a solid, an ice cube is a liquid. hope it helps
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Carbon burns in the presence of oxygen to give carbon dioxide. Which chemical equation describes this reaction?
sasho [114]
2.) carbon + oxygen → carbon dioxide 
6 0
3 years ago
Read 2 more answers
A mixture of calcium carbonate, CaCO3, and barium carbonate, BaCO3, weighing 5.40 g reacts fully with hydrochloric acid, HCl(aq)
amid [387]

Answer:

CaCO₃ = 85.18%

BaCO₃ = 14.82%

Explanation:

The acid will react with the salts, the partial reactions are:

CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O

BaCO₃ + 2HCl → BaCl₂ + CO₂ + H₂O

So, the total amount of CaCO₃ BaCO₃ will form the CO₂.

Using the ideal gas law to calculate the number of moles of CO₂:

PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant (0.082 atm*L/mol*K), and T is the temperature (50ºC + 273 = 323 K).

0.904*1.39 = n*0.082*323

26.486n = 1.25656

n = 0.05 mol

So, the number of moles of the mixture is 0.05 mol.

The molar masses of the components are:

CaCO₃ = 40 g/mol of Ca + 12 g/mol of C + 3*16 g/mol of O = 100 g/mol

BaCO₃ = 137.3 g/mol of Ba + 12 g/mol of C + 3*16 g/mol of O = 197.3 g/mol

Let's call x the number of moles of CaCO₃ and y the number of moles of BaCO₃, so:

100x + 197.3y = 5.4

x + y = 0.05 mol

y = 0.05 - x

100x + 197.3*(0.05 - x) = 5.4

100x - 197.3x = 5.4 - 9.865

97.3x = 4.465

x = 0.046 mol of CaCO₃

y = 0.004 mol of BaCO₃

So, the masses are:

CaCO₃ = 100* 0.046 = 4.60 g

BaCO₃ = 137.3*0.004 = 0.80 g

The percentages in the mixture are:

CaCO₃ = (4.60/5.40)*100% = 85.18%

BaCO₃ = (0.80/5.40)*100% = 14.82%

4 0
3 years ago
Explain why calcium metal after reacting with water starts floating on its surface. Write the chemical equation for this reactio
Oksanka [162]

Firstly, the chemical equation between the calcium metal and water will be:  

Ca(s) + 2 H₂O(l) → Ca(OH)₂(aq) + H₂(g)  

We can see from the equation the bubbles of hydrogen gas which are formed during the reaction stick to the surface of the metal and hence calcium floats on water.  

The other metal that will float on the water during the reaction is magnesium which have the same chemical behavior like calcium, we can illustrate that by the chemical equation:

Mg(s) + 2 H₂O(l) → Mg(OH)₂(aq) + H₂(g)

3 0
3 years ago
Where on the periodic table are the majority of radioactive isotopes found?
Oliga [24]
Periodic table is an arrangement of chemical elements in an organized manner with atomic number. Elements are distributed in columns and groups in periodic table according to their properties.
Many elements have their isotopes and mostly are radioactive but isotopes are not mentioned on the periodic table, elements are mentioned there and all trans-uranium elements are most radioactive.
5 0
3 years ago
Select the true statement for the following reaction: N2 + 3 H2 → 2 NH3 1. Each N atom is reduced from 0 to +3. Each H atom is o
ELEN [110]

Answer: option 2

Explanation: each nitrogen is reduced from zero to -3 and Each H is Oxidised from 0 to +1

Since oxidation no of Nitrogen in molecular N2 is always zero and for H2 also zero.

In NH3, x+3(+1)=0

X+3=0

X=-3

And and hydrogen shows +1 Oxidation no when it is combined with non metal(like N,O,cl) and with -2 with metal like Na,Ca etc.

And zero in molecular form H2.

7 0
3 years ago
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