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snow_lady [41]
3 years ago
9

1.Which of the following are considered pure substances

Chemistry
1 answer:
PilotLPTM [1.2K]3 years ago
5 0
1.) homogeneous mixtures

2.) <span>NaCI, because sodium is a metal and chlorine is a nonmetal</span>

3.) I'm thinking the first the option 
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The number of _______________ in the nucleus determines an element's atomic number. this number defines the name of the element,
AleksandrR [38]

The number of <u>protons</u> in the nucleus determines an element's atomic number.

4 0
3 years ago
How many grams sodium bromide can be formed from 51 grams of sodium hydroxide?
raketka [301]

Explanation:

When working with moles only, you will start by applying stoichiometry to determine how the reactants will affect your amount of products in this reaction. For this question, we will assume that other reactants are in infinite qualities, so therefore, it is the amount of aluminum that we will be concerned with. You need to figure out how much aluminum is in the specified amount of aluminum bromide, and then how much aluminum hydroxide that will be able to create. Make sure all your units cancel out!

9.24 mol AlBr3 x (1 mol Al / 1 mol AlBr3) x (1 mol Al(OH)3 / 1 mol Al) = 9.24 mol AlBr3

When you're working with mole ratios that involve grams to moles conversions, the first thing you want to do is calculate the molecular weight of each component you are being asked about. Because the question was given to you as words instead of chemical formulas, you will want to figure out the chemical formulas. For example, aluminum hydroxide is Al(OH)3 and aluminum bromide is AlBr3. To calculate molecular weight, you will want to consult a periodic table, find the molecular weight for each atom, and then calculate the correct sum of each molecular weight. Make sure you keep track of the number of each atom you have, i.e. 3 oxygen and 3 hydrogen for aluminum hydroxide.

Na = 22.990 g/mol

O = 15.999 g/mol

H = 1.008 g/mol

NaOH = 22.990 g/mol + 15.999 g/mol + 1.008 g/mol = 39.997 g/mol

Al = 26.982 g/mol

O = 15.999 g/mol

H = 1.008 g/mol

Al(OH)3 = 26.982 g/mol + (3 x 15.999 g/mol) + (3 x 1.008 g/mol) = 78.003 g/mol

Now, if you begin with an amount of NaOH in grams, you will first have to convert that to moles in order to use the mole ratio.

24 g NaOH x (1 mol NaOH / 39.997 g NaOH) = 0.600 mol NaOH

Now, you will have to account for the part of the sodium hydroxide that will be present in the aluminum hydroxide. In this case, it is the hydroxide (OH) portion of the formula. There is one mole of OH in each mole of NaOH, but there are 3 moles of OH in each mole of Al(OH)3. You will start with the 0.600 mol NaOH you know you have and then use the mole ratio.

0.600 mol NaOH x (1 mol OH / 1 mol NaOH) x (1 mol Al(OH)3 / 3 mol OH) = 0.200 mol Al(OH)3

Finally, when you are converting from grams to grams, you will have to find the molecular weight of both the reactant and the product, convert reactants in grams to reactants in moles, then use the mole ratio, then convert the moles of product back to grams of product. This time, you are concerned about the mole ratio of sodium, as that is the element that is in both chemical formulas.

7 0
2 years ago
True or False When one side of a molecule is electronegative (δ-) and the other side of the
lesya [120]

Answer:

True; When one side of a molecule is electronegative (δ-) and the other side of the

molecule is electropositive (δ+), it is said to have a dipole moment.

Explanation:

A dipole moment exists in a molecule as a result of differences in the electronegativity values between the atoms of the elements involved in the chemical bonding.

When a strogly electronegative atom such as oxygen or chlorine is chemically bonded to a less electronegative or an electropositive atom such as hydrogen, there is an uneven sharing of the electrons involved in the bonding. The more electronegative atoms tends to draw the shared electrons mostly to themselves. This induces a partially negative charge (δ-) on them while leaving the electropositive atoms with a partially positive charge (δ+).

Water is an example of a molecule having a dipole moment. The oxygen atoms are more electronegative than hydrogen and as such draw the shared electrons to themselves more, inducing a partial positive charge (δ+) on the hydrogen atoms while they themselves develop a partial negative charge (δ-).

8 0
3 years ago
Which statement is incorrect?
Katena32 [7]

Answer:

e. When the indicator changes color and remains, 2 more drops of the solution in the buret should be added.

Explanation:

<em>Which statement is incorrect? </em>

<em>Select one: </em>

<em> a. The volume of solution in the buret should be recorded when the endpoint is reached. </em> CORRECT. At the endpoint, the titrant is expected to have completely reacted with the titrand.

<em>b. It is good practice to place the flask over a white background to better observe the color change of the solution.</em>  CORRECT. Using a white background makes it easier to detect the changes in the color of the indicator.

<em>c. The endpoint is when the indicator changes color.</em> CORRECT. This is the function of an indicator.

<em>d. Phenolphthalein will go from a colorless solution to a pink solution for the addition of NaOH to an acid solution.</em>  CORRECT. Phenolphthalein is colorless when pH < 8.3 and it is pink when pH > 10.0.

<em>e. When the indicator changes color and remains, 2 more drops of the solution in the buret should be added.</em> INCORRECT. When the endpoint is reached, no more titrant should be added.

4 0
3 years ago
Why are gamma rays not able to reflect off a mirrors surface
ElenaW [278]

Answer:

the Ray's go right through it

Explanation:

the Ray's are so small they punch right through them

7 0
3 years ago
Read 2 more answers
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