All categories

3 years ago

How many joules of heat energy are released when 50.0 g of water are cooled from 70.00C to 60.00C?

Chemistry

1 answer:

baherus [9]3 years ago

5 0

Answer:

2090 joules are released.

Explanation:

Calorimetry is applied to this problem:

Q = m . C . (Final T° - Initial T°)

C is the Specific Heat, a constant for each substance, that determines the heat per unit mass, which is required to raise one degree Celsius.

C for water is 4.18 kJ /kg.°C

We convert the mass of water to kg

50 g . 1kg / 1000 g = 0.05 kg

Let's replace data in the formula:

Q = 0.05 kg . 4.18 kJ /kg.°C (60°C - 70°c)

Q = -2.09 kJ

As we have a negative value, heat is released. We need the |Q| for the value

2.09 kJ . 1000 J /kJ = 2090 joules

You might be interested in

The element thallium is 70% thallium-205 and 30% thallium-203. Calculate its relative atomic mass to 1 decimal place.

xxMikexx [17]

Answer:

answer-

The relative atomic mass = 204.4

explanation:

Thallium -203 = 30%

Thallium -205 = 70%

Therefore ,

relative mass of thallium = (30×203 + 70×205)/100

relative mass of thallium = (20440)/100

relative mass of thallium = 204.40 amu

Thus,

relative atomic mass of thalium =204.4 ( to 1 decimal place)

6 0

3 years ago

What is the pH difference of two samples if the concentration of [H+] ions is 1000-fold less in the second sample?

snow_tiger [21]

The correct answer is a. This is because the pH of a solution is defined as -log10(concentration of H+ ions). An inverse logarithmic scale such as this means that a solution with a lower concentration of H+ ions will have a higher pH than one with a higher concentration. Therefore we know that the pH of the second sample will be higher than the first.

Since the logarithmic scale has the base 10, a change by 1 on the scale is a consequence of multiplication/division of the H+ concentration by a factor of 10. As the scale is inverse, this means that a decrease of concentration by factor 1000 is equivalent to increasing the pH by (1000/10) = 3.

4 0

3 years ago

Read 2 more answers

The amount ofcalcium present in milk can be determined by adding oxalate to asample and measuring the massof calcium oxalate pre

Sauron [17]

<u>Answer:</u> The mass percent of calcium in milk is 0.107 %

<u>Explanation:</u>

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 calcium oxalate = 0.429 g

Molar mass of calcium oxalate = 128.1 g/mol

Putting values in equation 1, we get:

$\text{Moles of calcium oxalate}=\frac{0.429g}{128.1g/mol}=0.0033mol$

The given chemical equation follows:

$Na_2C_2O_4(aq.)+Ca^{2+}(aq.)\rightarrow CaC_2O_4(s)+2Na^+(aq.)$

Sodium oxalate is present in excess. So, it is considered as an excess reagent. And, calcium ion is a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

1 mole of calcium oxalate is produced from 1 mole of calcium ion

So, 0.0033 moles of calcium oxalate is produced from = $\frac{1}{1}\times 0.0033=0.0033mol$ of calcium ions