Learning calculations in chemistry

If 45.0 mL of ethanol (density = 0.789 g/mL) initially at 8.0 ∘C is mixed with 45.0 mL of water (density = 1.0 g/mL) initially a

strojnjashka [21]

Answer : The final temperature of the mixture is, $22.14^oC$

Explanation :

First we have to calculate the mass of ethanol and water.

$\text{Mass of ethanol}=\text{Density of ethanol}\times \text{Volume of ethanol}=0.789g/mL\times 45.0mL=35.5g$

and,

$\text{Mass of water}=\text{Density of water}\times \text{Volume of water}=1.0g/mL\times 45.0mL=45.0g$

Now we have to calculate the final temperature of the mixture.

In this problem we assumed that heat given by the hot body is equal to the heat taken by the cold body.

$q_1=-q_2$

$m_1\times c_1\times (T_f-T_1)=-m_2\times c_2\times (T_f-T_2)$

where,

$c_1$ = specific heat of ethanol = $2.42J/g^oC$

$c_2$ = specific heat of water = $4.18J/g^oC$

$m_1$ = mass of ethanol = 35.5 g

$m_2$ = mass of water = 45.0 g

$T_f$ = final temperature of mixture = ?

$T_1$ = initial temperature of ethanol = $8.0^oC$

$T_2$ = initial temperature of water = $28.6^oC$

Now put all the given values in the above formula, we get:

$35.5g\times 2.42J/g^oC\times (T_f-8.0)^oC=-45.0g\times 4.18J/g^oC\times (T_f-28.6)^oC$

$T_f=22.14^oC$

Therefore, the final temperature of the mixture is, $22.14^oC$

3 0

3 years ago

Express 749 000 000 in scientific notation,

Dima020 [189]

Answer:

7.49 × 108

Explanation:

Scientific notation is a way to express numbers in a form that makes numbers that are too small or too large more convenient to write. It is commonly used in mathematics, engineering, and science, as it can help simplify arithmetic operations. In scientific notation, numbers are written as a base, b, referred to as the significant, multiplied by 10 raised to an integer exponent, n, which is referred to as the order of magnitude:

8 0

3 years ago

Why would two poles of different magnets attract each other?

Kruka [31]

When two magnets are brought near each other, like poles repel; opposite poles attract. When a magnet is brought near a piece of iron, the iron also gets attracted to the magnet, and it acquires the same ability to attract other pieces of iron.

3 0

2 years ago

If 10.00 g of iron metal is burned in the presence of excess of O2 how many grams of Fe2O3 will form

sergiy2304 [10]

14.292 grams of Fe2O3 is formed when 10 gram of iron metal is burned.

Explanation:

The balanced equation for the reaction is to be known so that number of moles taking part can be known.

The balanced chemical equation is

4Fe + 3 $O_{2}$ ⇒ 2 $Fe{2}$ $O{3}$

From the given weight of iron to be used for the production of $Fe{2}$ $O{3}$ , number of moles of Fe taking part in the reaction can be known by the formula:

Number of moles= mass ÷ Atomic mass of one mole of the element.

(Atomic weight of Fe is 55.845 gm/mole)

Putting the values in equation

Number of moles = 10 gm ÷ 55.845 gm/mole

= 0.179 moles

Applying the stoichiometry concept

4 moles of Fe gives 2 Moles of Fe2O3

0.179 moles will produce x moles of Fe2O3

So, 2÷ 4 = x ÷ 0.179

2/4 = x/ 0.179

2 × 0.179 = 4x

2 × 0.179 / 4 = x

x = 0.0895 moles

So from 10 grams of iron metal 0.0895 moles of Fe2O3 is formed.

Now the formula used above will give the weight of Fe2O3

weight = atomic weight × number of moles

= 159.69 grams × 0.0895

= 14.292 grams of Fe2O3 formed.

4 0

2 years ago

PLEASE ANSWER THIS QUESTION FAST :(

kramer

Mol sulfuric acid = 19 g * (1 mol) / (98.1 g) = 0.19367 mol
mol H2O = 0.19367 mol H2SO4 * (2 H2O) / (1 H2SO4)
= 0.387359 mol H2O
grams H2O = 0.387359 mol H2O * (18 g)/(1 mol)
= 6.97 g
The answer is 7.0 grams of water

6 0

2 years ago