1.The atomic mass unit is presently based on assigning a mass of exactly 12 amu to:

(a) an atom of carbon isotope ¹³C      (b) an atom of carbon isotope ¹²C     (c) all carbon atoms

(d) the average atomic mass of carbon

Which of the following samples contain the greatest number of oxygen atoms?

(a) 1mol H₂O (b) 3 x 10²³ molecules O₃    (c) 1mol CO₂   (d) 1mol CO

Approximately, how many oxygen molecules are in a 16.00 g sample of oxygen?

(a) 1 x 10²³    (b) 2 x 10²³    (c) 3 x 10²³    (d) 6 x 10²³     (e) 8 x 10²³   

The number of moles of nitric acid (HNO₃) present in 126.04 g of nitric acid is:

   (a) 1    (b) 2    (c) 0.5    (d) 1.5

Which one of the following is a correct expression for molarity?

   (a) mol solute/L solvent     (b) mol solute/L solution       (c) mol solvent/L solution

   (d) mol solution/L solvent

How many grams of potassium chloride are there in 100.0 ml of 1.50 M KCl ?

   (a) 11.2 g (b)112 g ( c) 1.12 g (d) None of these

Which statement is not true?

   (a) 1 mole of Na₂CO₃ contains same number of Na⁺ cations as CO₃^2- anions

   (b) 1 mole of Na₂CO₃ contains twice as many Na⁺ cations as CO₃^2- anions

   (c) 1 mole of Na₂CO₃ contains Na⁺ cations and CO₃^2- anions in the ratio 2:1

   (d) 1 mole of Na₂CO₃ contains twice the Avogadro number of Na⁺ cations

Which one of the following molecular formulas is not an empirical formula?

   (a) CHO     (b) C₂H₂O₃     (c) C₆H₉O₃       (d) C₁₂H₁₄O₃      (e) C₁₄H₁₂O₃

​Please help!!!

Balance the following redox reaction if it occurs in basic solution. What are the coefficients in front of Br2 and OH⁻ in the balanced reaction? Br2(l) → BrO3⁻(aq) + Br⁻(aq)

We are using 0.75 g of 1,2-dibromo-1,2-diphenylethane adn reacting with 0.75g KOH and 5 mL triethylene glycol to produce diphenyl acetylene.

What is the theoretical yield?

home / study / science / biology / questions and answers / which of the following best explains why atp is ... Question: Which of the following BEST explains why ATP is a ... Save Which of the following BEST explains why ATP is a positive regulator of aspartate transcarbamoylase (ATCase)? A. Aspartate is only available when ATP levels are high. B. ATP levels correspond to CTP levels, thus when both ATP and CTP are high, ATCase is active. C. Nucleic acids should only be produced when ATP levels are high. D. ATP always converts allosteric enzymes from the T state to the R state. E. None of the answers is correct.

Which of the following about covalent bonding are true?

1.There is free rotation around a pi bond

2.There is free rotation around a sigma bond

3. The electron density in a pi bond is concentrated along the bond axis between atoms in the bond

4. Atoms that are connected by only a sigma bond are further apart and are connected by both a sigma and pi bond

Vapour Pressure of Solutions of Non-Volatile or Volatile Solutes 22.555 g of a non-volatile solute is dissolved in 215.0 g of water. The solute does not react with water nor dissociate in solution. Assume that the resulting solution displays ideal Raoult's law behaviour. At 10°C the vapour pressure of the solution is 9.073 torr. The vapour pressure of pure water at 10°C is 9.209 torr. Calculate the molar mass of the solute (g/mol). See example 17.1 on pp865-6 of Zumdahl ''Chemical Principles'' 7th ed. 1pts Submit Answer Tries 0/5 Now suppose, instead, that 22.555 g of a volatile solute is dissolved in 215.0 g of water. This solute also does not react with water nor dissociate in solution. The pure solute displays, at 10°C, a vapour pressure of 0.921 torr. Again, assume an ideal solution. If, at 10°C the vapour pressure of this solution is also 9.073 torr. Calculate the molar mass of this volatile solute.

How much heat is released when 28.0 g of lithium metal reacts as shown below? (Answer should come out to 448 kJ)

2 Li (s) + 2 H₂O (ℓ) → 2 LiOH (s) + H₂ (g) ΔHº = −222 kJ

A 46.0%/54.0% by volume propane/n-butane mixture is cooled from 255°C to 193°C. FInd the change in ethalpy of this mixture by following the steps below. Assume ideal behavior. a) What is the average molar mass of the mixture? b) What is the change in specific enthalpy of pure propane from 255°C to 193°C? c) What is the change in specific enthalpy of pure n-butane from 255°C to 193°C? d) What is the change in specific enthalpy of the mixture from 255°C to 193°C? e) What is the change in enthalpy of the mixture from 255°C to 193°C in kJ/kg?

You want to make 750.00 mL of a 0.9550 M aqueous solution of Cr(NO3)2. You have available in lab a bottle of pure Cr(NO3)2 ∙ 6 H2O (s), a bottle of 1.672 M Cr(NO3)2 solution and a bottle of 0.5005 M Cr(NO3)2.

a) How many grams of the Cr(NO3)2 ∙ 6 H2O (s) would you need to use to prepare the desired solution?

b) How many mL of the 1.672 M Cr(NO3)2 solution would you need to use to prepare the desired solution?

c) Describe how you could use the 0.5005 M Cr(NO3)2 solution to prepare the desired solution.

Refer Appendix G in the text in order to determine the standard free energy change for each of these reactions. Determine whether or not the reaction is spontaneous under standard conditions (298 K, 1 atm). 2??3 → ?2 + 3?2 ???4 (?) + ?2 (?) → ???2 (?) + 2?2?(?) ?(???????) → ?(????ℎ???)

Which one of the following has the lowest vapor pressure at 25 degrees celsius? a) CH3OH b) HOCH2CH2OH c) CH3OCH3 d) CH3CH2OH

During a Structure and Solubility experiment how do you distinguish between the following:

a.) butane and 2-chlorobutane

b.)butane and 1-butanol

c.)1-butanol and 2-butanol

d.)1-butanol and butanoic acid

Can somebody explain to me the miscibility of isopropanol alcohol and ethanol alcohol in a NaCl solution and why higher levels of concentration of salt solution make the alcohol less miscible (homogeneous)?

a)What is the mass (in grams) of the solid product when 7.5 g of silver nitrate reacts in solution with excess sodium carbonate?AgNO₃(aq) + Na₂CO₃(aq) --> Ag₂CO₃(s) + NaNO₃(aq) [unbalanced]

b)What is the mass (in grams) of the precipitate when 7.62 g of silver nitrate reacts in solution with excess sodium phosphate?AgNO₃(aq) + Na₃PO₄(aq) --> Ag₃PO₄(s) + NaNO₃(aq) [unbalanced]

Mutliple step synthesis for 4-bromoacetanilide from aniline

1. during the synthesis of aniline from nitrobenxe, explain why it was necessary to make the solution alkaline (addition of NaOH)

2. During filtration, why is it important to only wash the solid with ice-cold solvent?

3. Why is it necessary ti acylate aniline prior to bromination?

4. If the synthesis of p-bromoacetanilide also provided a small amount of o-bromoacetanilide after the crystallixation step, how would that influence the melting point range od p-bromoacetanilide?