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3 years ago

How many significant figures are in this number? : 2.7 x 10^-3

Chemistry

1 answer:

Lady_Fox [76]3 years ago

6 0

Answer:

2 significant figures i.e. 2 and 7.

Explanation:

We need to find the number of significant figures in the given number i.e. $2.7\cdot10^{-3}$ .

It has 2 significant figures i.e. 2 and 7.

It means the power of 10 doesn't count in the significant figures.

Hence, there are 2 significant figures.

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15. A food sample contains 25 g carbohydrate, 8 g fat and 5 g protein. The energy content is:

Musya8 [376]

Answer:

C) 170 Cal

Explanation:

We are given the composition of a food sample as;

Carbohydrate = 25 g

fat = 8 g

Protein = 5 g

We are needed to determine the energy content of the food;

We need to know the amount energy yielded by each food substance.

That is; carbohydrates and proteins generate 4 calories per gram while fats generates 9 calories per gram.

Therefore;

Amount of energy will be;

= (25 × 4 cal/g) + (8g × 9 cal/g) + (5 g × 4 cal/g)

= 172 cal

Approximately , 170 calories

Therefore, the energy content will be 170 calories

6 0

3 years ago

Ice has a density of 0.92g/cm3. It will float in water.

SVEN [57.7K]

The density of pure water is 1 g/cm^3.

Its density is 0.98 g cm 3 at room temperature, in comparison with the handiest zero.92 g cm 3 for ice, a reality that has to be defined through atomic, and molecular concepts. If ice has been no longer much less dense than water, it might sink, having a devastating impact on lake backside ecosystems. believe it or now not, ice is honestly about 9% much less dense than water. for the reason that water is heavier, it displaces the lighter ice, causing the ice to glide to the pinnacle.

The density of ice is about 90 percent that of water, but that could range because ice can contain air, too. meaning that about 10 percent of an ice cube or iceberg will be above the water line. The density of water is maximum at four∘C, and the density of the ice is much less than the water due to its susceptible intermolecular pressure of attraction. as the density of water is more, it's miles heavier than ice. therefore ice floats on the floor of the water. Ice continually floats due to the fact it's far less dense than everyday water. because frozen water molecules shape a crystal.

Learn more about A density here:-brainly.com/question/17780219

#SPJ9

6 0

1 year ago

White phosphorus, P4, is prepared by fusing

damaskus [11]

2Ca3(PO4)2 + 6SiO2 + 10C ---> P4 + 6CaSiO3 + 10CO

1 mole of Ca3(PO4)2 = 310g
1 mole of P4 = 124g

according to the reaction:
2*310g Ca3(PO4)2----------------124g P4
x g Ca3(PO4)2 ------------------------ 30g P4
x = 150g Ca3(PO4)2

so, your answer is good

3 0

3 years ago

If 6.96 mol of C 5 H 12 reacts with excess O 2 , how many moles of CO 2 will be produced by the following combustion reaction? C

kati45 [8]

Answer:

34.8 moles of CO₂ are produced

Explanation:

This is the reaction:

1C₅H₁₂ + 8O₂ → 6H₂O + 5CO₂

Ratio is 1:5. We make a rule of three

1 mol of pentane can produce 5 moles of CO₂

Then, 6.96 moles of pentane may produce (6.96 .5) / 1 = 34.8 moles

7 0

3 years ago

Each 5-ml teaspoon of Extra Strength Maalox Plus contains 450 mg of magnesium hydroxide and 500 mg of aluminum hydroxide. How ma

Art [367]

Answer:

0.0347 moles of hydronium ions

Explanation:

The equation of the neutralization reaction between hydroxide and hydronium ions is given below:

H₃O+ (aq) + OH- (aq) ----> 2 H₂O (l)

From the equation above, 1 mole of hydroxide ions will neutralize one mole hydronium ions.

The moles of hydroxide ions present in 1 teaspoon or 5 mL of antacid product is calculated as follows:

Number of moles = mass / molar mass

Molar mass of Magnesium hydroxide, Mg(OH)₂ = 58 g/mol

Molar mass of aluminium hydroxide, Al(OH)₃ = 78 g/mol

Mass of magnesium hydroxide = 450 g = 0.45 g

Mass of aluminium hydroxide = 500 mg = 0.5 g

Moles of magnesium hydroxide = (0.45/58) moles

Moles of aluminium hydroxide = (0.5/78) moles

Equation of the ionization of magnesium hydroxide and aluminium hydroxide is given below:

Mg(OH)₂ (aq) ----> Mg²+ (aq) + 2 OH- (aq)

Al(OH)₃ (aq) ---> Al³+ (aq) + 3 OH- (aq)

Number of moles of hydroxide ions present in (0.45/58) moles of magnesium hydroxide = 2 × (0.45/58) moles = 0.0155 moles

Number of moles of hydroxide ions present in (0.5/78) moles of aluminium hydroxide = 3 × (0.5/78) moles = 0.0192 moles

Total moles of hydroxide ions = 0.0155 + 0.0192 = 0.0347 moles hydroxide ions

Therefore, 0.0347 moles of hydroxide ions will neutralize 0.0347 moles of hydronium ions.

3 0

3 years ago