Answer:
aqueous solutions of silver nitrate and sodium chloride turn cloudy after mixing aqueous solutions of hydrochloric acid and sodium hydrogen carbonate produces bubbles on mixing Sodium hydroxide is mixed with water and the container feels warmer
Explanation:
A chemical change involves the formation of new substances. Also heat is absorbed or released in a chemical change. Another name for a chemical change is a chemical reaction.
In the first case, a reaction of the sort;
AgNO3(aq) + NaCl(aq) ---> AgCl(s) + NaNO3(aq)
The cloudy solution is due to the formation of AgCl precipitate.
In the second case, a reaction of the sort;
HCl(aq) + NaHCO3(aq) ---> NaCl(aq) + CO2(g) + H2O(l)
The gas evolved is due to the formation of CO2 in the process. Heat is also evolved showing that it is a chemical change.
Answer:
4. 2.0 M CaC12(aq)
Explanation:
According to the van't Hoff factor, (the measurement of the solute's colligative properties effect (boiling point,freezing point depression)) a solution that has the highest point at standard pressure, id the one with the most particles or ions.
van't Hoff factor can also be described as the ratio between the original concentration of the solutions's atoms when the solution is dissolved and the concentration of the solutions taken from its mass.
Answer:
The possible options are :
(1) 1.0 M KC1(aq) (3) 2.0 M KCl(aq) (2) 1.0 M CaC12(aq) (4) 2.0 M CaC12(aq)
Answer is (4) 2.0 M CaC12(aq)
Explanation:
vant Hoff factor highest BP has the most particles...ions CaCl2 forms 3 ==> Ca2+ and 2Cl-.
The van 't Hoff factor i (named after Dutch chemist Jacobus Henricus van 't Hoff) is a measure of the effect of a solute upon colligative properties such as osmotic pressure, relative lowering in vapor pressure, boiling-point elevation and freezing-point depression.
b. 56.00 s ( a time measured by a stopwatch)
c. 4 choices ( the number of choices in this list)
d. 3 lbs ( the weight of an object measured on a scale )
Answer: a. 2.54 cm ( the number of centimeters in exactly 1 in) and c. 4 choices ( the number of choices in this list)
Justification:
1) a. 2.54 cm ( the number of centimeters in exactly 1 in)
Although the exact length of one inch has varied in the past, currently the inch is defined as exactly 2.54 cm, so this is an exact number.
b. 56.00 s ( a time measured by a stopwatch)
The time measured by a stopwatch is not an exact number. The number is limited by the precision of the instrument (the stopwatch) and it migh have been 56.004 instead of 56.00, and the stopwatch cannot shoe that. So, this is not an exact number.
c. 4 choices ( the number of choices in this list)
This is, indeed an exact number. It is 4, not 4.1, nor 3.9, nor any other number.
d. 3 lbs ( the weight of an object measured on a scale )
As reasoned with the stopwatch, this measure, 3 lbs, is subject to the precision of the scale. It is not an exact number. It could be other number close to 3: 2.99 for example.
These are exact numbers: c. 4 choices ( the number of choices in this list) and d. 3 lbs ( the weight of an object measured on a scale )
The exact number is a value that is known with complete certainty. Examples are counted numbers of objects or certain unit conversions such as exactly 3 feet in 1 yard. Another example is, a dozen is defined as 12 objects, and a pound is defined as 16 ounces.
Fraction an exact number is a fraction takes two integers and places them in a ratio, for example 3/4 or 10/15. A decimal can express the same numerical quantity, but it does so with a single number (like 0.75 or 0.66). So, the fraction makes the relationship among numbers clear in the way it is written.
While a decimal can express the same numerical quantity, but it does so with a single number (like 0.75 or 0.66).
a. 2.54 cm ( the number of centimeters in exactly 1 in) is decimal
b. 56.00 s ( a time measured by a stopwatch) is not exact numbers
c. 4 choices ( the number of choices in this list) is exact numbers
d. 3 lbs ( the weight of an object measured on a scale ) is exact numbers
Grade: 9
Subject: chemistry
Chapter: exact number
Keywords: exact number
B. The subscript 2 indicates that two atoms of oxygen are present in the substance.
C. The chemical symbol Al indicates that oxygen is present in the substance.
D. The subscript 2 indicates that two atoms of aluminum are present in the substance
In the formula Al2O3, the subscript 2 indicates the presence of two atoms of Aluminium, and the subscript 3 indicates the presence of three atoms of Oxygen.
The formula Al2O3 is for aluminium oxide. The coefficient and subscript in this formula tell us about the number of atoms of each element present in the compound. In this case:
So, the correct answer to the question is, the subscript 2 indicates that two atoms of aluminum are present in the substance (option D).
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Molecular compounds can not conduct electricity because they do not break up into ions. Therefore, option (A) is correct.
Molecular compounds can be characterized as those compounds where the atoms are connected by covalent bonds. The covalent bond is generally created by the mutual sharing of electrons by the atoms. In molecular compounds, intermolecular forces are responsible for bond formation.
The melting point of the molecular compound is low as compared to the ionic compound as the energy required to break bonds is less compared to the ionic bond between ions in the crystalline ionic compound.
Molecular compounds are generally by the reaction between non-metals. Molecular compounds are also known as covalent compounds. The ionic and molecular compound differ from each in their physical properties,
The molecular compounds do not conduct electricity as they do not bark into ions. Therefore they can behave as insulators while ionic compounds conduct electricity.
Learn more about Molecular compounds, here:
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The moon surface isvisible to an observer on earth due to the gravitational force that attracts themoon to the earth. The more massive the body is, the more the smaller body isattracted to the larger body. We can only see the side of the moon due to thespeed at which the moon rotates.