Chemistry College


1. Calculate the heat (expressed in calories) required to heat 115 g of water from
15.4 °C to 91.4 °C.

Answers

Answer 1

115 grams in water need 8740 calories' worth of heat to be heated to 15.4 °C to 91. 4 °C.

How are calories created?

A calorie is an unit of energy measurement. It is, in fact, the quantity of energy needed to increase the temperature among one mL (or one gram) of freshwater with one degrees C.

q = m * c * ΔT

where:

q = heat (in calories)

m = mass of water (in grams)

c = specific heat capacity of water (in calories per gram per degree Celsius)

ΔT = change in temperature (in degrees Celsius)

The specific heat capacity of water is 4.18 J/g°C, or 1 calorie/g°C.

ΔT = 91.4 - 15.4 = 76

Substituting the values into the formula:

q = 115 g * 1 calorie/g°C * 76°C = 8740 calories

So, the heat required to heat 115 grams of water from 15.4 °C to 91.4 °C is 8740 calories.

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Related Questions

A solution of sodium phosphate is prepared by dissolving 3.95 g of sodium phosphate in water and diluting it to 300.0 mL. What is the Molarity, M, of the salt and each of the ions?

Answers

3.95 g of sodium phosphate are dissolved in 300.0 mL of water to create a solution of sodium phosphate. The sodium ions' molality is 1.473 m

As opposed to molality, why is molarity used?

Molality is based also on kilograms of solvent, whereas molarity is predicated on the liter of solution. When researching the characteristics of solutions associated to vapor pressure conditions fluctuations, concentrations given in molality are utilized. Because its value is unaffected by temperature fluctuations, molality is employed.

Molarity is moles of solute per litre of solution

Molality is moles of solute per kg of solvent.The volume of solution = 1 L

The mass of solution = volume X density = 1000mL X 1.43 = 1430 grams

The mass of solute = moles X molar mass of sodium phosphate = 0.65X164

mass of solute = 106.6 grams

the mass of solvent = 1430 - 106.6 = 1323.4 grams = 1.3234 Kg

the molality =

Thus molality of sodium phosphate is 0.491 m

Each sodium phosphate of molecule will give three sodium ions.

Thus molality of sodium ions = 3 X 0.491 = 1.473 m

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Zeros at the end of a number are not significant if the number contains a decimal point?
True or False

Answers

Answer:

False

Explanation:

Here's a little guide as to when zeros are significant digits.

Zeros ARE significant digits when they are at the end of a number with a decimal point.

Zeros ARE significant digits when they are in the middle of two nonzero numbers.

Zeros are NOT significant digits when they are at the beginning of a number.

Hope this helps! :)

One of the hydrates of CoCl2 is cobalt(II) chloride dihydrate . A 56.2 gram sample of CoCl2 2 H2O was heated thoroughly in a porcelain crucible, until its weight remained constant. After heating, how many grams of the anhydrous compound remained?

Answers

The formula for cobalt(II) chloride dihydrate is CoCl2 · 2H2O, which means that each mole of this compound contains 1 mole of CoCl2 and 2 moles of H2O. To find the number of moles of CoCl2 in 56.2 grams of CoCl2 · 2H2O, we need to first find the molar mass of the compound:

Molar mass of CoCl2: 58.933 g/mol

Molar mass of 2H2O: 36.032 g/mol (2 × 18.016 g/mol)

Molar mass of CoCl2 · 2H2O: 58.933 g/mol + 36.032 g/mol = 94.965 g/mol

Now we can find the number of moles of CoCl2 in 56.2 grams of CoCl2 · 2H2O:

56.2 g / 94.965 g/mol = 0.591 moles

Since each mole of CoCl2 · 2H2O contains 1 mole of CoCl2, there are also 0.591 moles of CoCl2 in the sample.

We are told that the hydrate was heated until its weight remained constant, which means that all of the water was driven off and only the anhydrous CoCl2 remained. If the percent yield of the reaction was 100%, we would expect to recover the same amount of CoCl2 that was in the original sample (0.591 moles). However, we are told that the percent yield was only 65.5%, which means that the actual amount of CoCl2 recovered was:

0.655 × 0.591 moles = 0.387 moles

To find the mass of the anhydrous CoCl2 that remained, we can use the molar mass of CoCl2:

Molar mass of CoCl2: 58.933 g/mol

0.387 moles × 58.933 g/mol = 22.8 grams

Therefore, after heating, 22.8 grams of anhydrous cobalt(II) chloride remained.

give an example of a situation where a population must decide how to use limited land resources, and the foreseeable effect of that decision

Answers

An example of a situation where a population must decide how to use limited land resources is the development of urban areas.

How can the development of urban areas affect limited land resources ?

As the population grows and the demand for housing and commercial space increases, the decision must be made on how to allocate the limited land resources. One option may be to prioritize residential development, leading to urban sprawl and potentially resulting in loss of agricultural land and green spaces.

Another option may be to focus on sustainable development, preserving green spaces and promoting denser housing developments. The effect of these decisions will likely have long-term implications on the environment, quality of life, and availability of resources for future generations.

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